1.
Iceland
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Iceland is a Nordic island country in the North Atlantic Ocean. It has a population of 332,529 and an area of 103,000 km2, the capital and largest city is Reykjavík. Reykjavík and the areas in the southwest of the country are home to over two-thirds of the population. Iceland is volcanically and geologically active, the interior consists of a plateau characterised by sand and lava fields, mountains and glaciers, while many glacial rivers flow to the sea through the lowlands. Iceland is warmed by the Gulf Stream and has a climate, despite a high latitude just outside the Arctic Circle. Its high latitude and marine influence still keeps summers chilly, with most of the archipelago having a tundra climate. According to the ancient manuscript Landnámabók, the settlement of Iceland began in the year 874 AD when the Norwegian chieftain Ingólfr Arnarson became the first permanent settler on the island. In the following centuries, Norwegians, and to a lesser extent other Scandinavians, emigrated to Iceland, the island was governed as an independent commonwealth under the Althing, one of the worlds oldest functioning legislative assemblies. Following a period of strife, Iceland acceded to Norwegian rule in the 13th century. The establishment of the Kalmar Union in 1397 united the kingdoms of Norway, Denmark, Iceland thus followed Norways integration to that Union and came under Danish rule after Swedens secession from that union in 1523. In the wake of the French revolution and the Napoleonic wars, Icelands struggle for independence took form and culminated in independence in 1918, until the 20th century, Iceland relied largely on subsistence fishing and agriculture, and was among the poorest in Europe. Industrialisation of the fisheries and Marshall Plan aid following World War II brought prosperity, in 1994, it became a part of the European Economic Area, which further diversified the economy into sectors such as finance, biotechnology, and manufacturing. Iceland has an economy with relatively low taxes compared to other OECD countries. It maintains a Nordic social welfare system that provides health care. Iceland ranks high in economic, political and social stability and equality, in 2013, it was ranked as the 13th most-developed country in the world by the United Nations Human Development Index. Iceland runs almost completely on renewable energy, some bankers were jailed, and the economy has made a significant recovery, in large part due to a surge in tourism. Icelandic culture is founded upon the nations Scandinavian heritage, most Icelanders are descendants of Germanic and Gaelic settlers. Icelandic, a North Germanic language, is descended from Old Norse and is related to Faroese
2.
Pressure system
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A pressure system is a relative peak or lull in the sea level pressure distribution. The surface pressure at sea level varies minimally, with the lowest value measured 870.0 hectopascals, pressure systems cause weather experienced locally. Pressure systems are analyzed by those in the field of meteorology within surface weather maps, a low-pressure area, or low, is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence that occur in upper levels of the troposphere, the formation process of a low-pressure area is known as cyclogenesis. Thermal lows form due to localized heating caused by greater sunshine over deserts, since localized areas of warm air are less dense than their surroundings, this warmer air rises, which lowers atmospheric pressure near that portion of the Earths surface. Large-scale thermal lows over continents help create pressure gradients that drive monsoon circulations, low-pressure areas can also form due to organized thunderstorm activity over warm water. When such an occurrence occurs over the tropics in concert with the Intertropical Convergence Zone, monsoon troughs reach their northerly extent in August and their southerly extent in February. When a convective low acquires a well-defined circulation in the tropics it is termed a tropical cyclone, tropical cyclones can form during any month of the year globally, but can occur in either the northern hemisphere or the southern hemisphere during November. Atmospheric lift caused by low-level wind convergence into the surface low brings clouds, the low-pressure areas cloudy skies act to minimize diurnal temperature extremes. Since clouds reflect sunlight, incoming solar radiation is less. At night, the effect of clouds on outgoing longwave radiation, such as heat energy from the surface. The stronger the area of low pressure the stronger the winds experienced in its vicinity, around the world, low-pressure systems are most frequently located over the Tibetan Plateau and in the lee of the Rocky mountains. In Europe, recurring low-pressure weather systems are known as depressions. The lowest recorded barometric pressure was 870 hectopascals, occurred in the Western Pacific during Typhoon Tip on 12 October 1979. High-pressure systems are associated with light winds at the surface and subsidence through the lower portion of the troposphere. In general, subsidence will dry out an air mass by adiabatic or compressional heating, thus, high pressure typically brings clear skies. During the day, since no clouds are present to reflect sunlight, there is more incoming solar radiation. At night, the absence of means that outgoing longwave radiation is not absorbed
3.
Atmospheric pressure
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Atmospheric pressure, sometimes also called barometric pressure, is the pressure exerted by the weight of air in the atmosphere of Earth. In most circumstances atmospheric pressure is approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation. On average, a column of air one square centimetre in cross-section, measured from sea level to the top of the atmosphere, has a mass of about 1.03 kilograms and that force is a pressure of 10.1 N/cm2 or 101 kN/m2. A column 1 square inch in cross-section would have a weight of about 14.7 lb or about 65.4 N and it is modified by the planetary rotation and local effects such as wind velocity, density variations due to temperature and variations in composition. The standard atmosphere is a unit of pressure defined as 101325 Pa, the mean sea level pressure is the average atmospheric pressure at sea level. This is the pressure normally given in weather reports on radio, television. When barometers in the home are set to match the weather reports, they measure pressure adjusted to sea level. The altimeter setting in aviation, is an atmospheric pressure adjustment, average sea-level pressure is 1013.25 mbar. In aviation weather reports, QNH is transmitted around the world in millibars or hectopascals, except in the United States, Canada, however, in Canadas public weather reports, sea level pressure is instead reported in kilopascals. The highest sea-level pressure on Earth occurs in Siberia, where the Siberian High often attains a sea-level pressure above 1050 mbar, the lowest measurable sea-level pressure is found at the centers of tropical cyclones and tornadoes, with a record low of 870 mbar. Pressure varies smoothly from the Earths surface to the top of the mesosphere, although the pressure changes with the weather, NASA has averaged the conditions for all parts of the earth year-round. As altitude increases, atmospheric pressure decreases, one can calculate the atmospheric pressure at a given altitude. Temperature and humidity affect the atmospheric pressure, and it is necessary to know these to compute an accurate figure. The graph at right was developed for a temperature of 15 °C, at low altitudes above the sea level, the pressure decreases by about 1.2 kPa for every 100 meters. See pressure system for the effects of air pressure variations on weather, Atmospheric pressure shows a diurnal or semidiurnal cycle caused by global atmospheric tides. This effect is strongest in tropical zones, with an amplitude of a few millibars and these variations have two superimposed cycles, a circadian cycle and semi-circadian cycle. The highest adjusted-to-sea level barometric pressure recorded on Earth was 1085.7 hPa measured in Tosontsengel
4.
Troposphere
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The troposphere is the lowest portion of Earths atmosphere, and is also where nearly all weather takes place. It contains approximately 75% of the mass and 99% of the total mass of water vapor. The average depths of the troposphere are 20 km in the tropics,17 km in the mid latitudes, the lowest part of the troposphere, where friction with the Earths surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to 2 km deep depending on the landform, atop the troposphere is the tropopause, which is the border between the troposphere and stratosphere. The tropopause is a layer, where the air temperature ceases to decrease with height. Most of the phenomena we associate with day-to-day weather occur in the troposphere, by volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor. The chemical composition of the troposphere is essentially uniform, with the exception of water vapor. The source of vapor is at the surface through the processes of evaporation. Thus the proportion of water vapor is normally greatest near the surface, the pressure of the atmosphere is maximum at sea level and decreases with altitude. This is because the atmosphere is nearly in hydrostatic equilibrium. The temperature of the troposphere generally decreases as altitude increases, the rate at which the temperature decreases, − d T / d z, is called the environmental lapse rate. The ELR is nothing more than the difference in temperature between the surface and the tropopause divided by the height. The reason for this difference is that the ground absorbs most of the suns energy. Meanwhile, the radiation of heat at the top of the results in the cooling of that part of the atmosphere. The ELR assumes the atmosphere is still, but as air is heated it becomes buoyant, when a parcel of air rises, it expands, because the pressure is lower at higher altitudes. As the air expands, it pushes the surrounding air outward. As energy transfer to a parcel of air by way of heat is very slow, such a process is called an adiabatic process
5.
Cyclogenesis
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Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere. Cyclogenesis is a term for at least three different processes, all of which result in the development of some sort of cyclone. Tropical cyclones form due to latent heat driven by significant thunderstorm activity, extratropical cyclones form as waves along weather fronts before occluding later in their life cycle as cold core cyclones. Mesocyclones form as warm core cyclones over land, and can lead to tornado formation, waterspouts can also form from mesocyclones, but more often develop from environments of high instability and low vertical wind shear. The anticyclonic equivalent, the process of formation of pressure areas, is anticyclogenesis. The opposite of cyclogenesis is cyclolysis, there are four main scales, or sizes of systems, dealt with in meteorology, the macroscale, the synoptic scale, the mesoscale, and the microscale. The macroscale deals with systems with global size, such as the Madden–Julian oscillation, synoptic scale systems cover a portion of a continent, such as extratropical cyclones, with dimensions of 1, 000-2,500 km across. The mesoscale is the smaller scale, and often is divided into two ranges, meso-alpha phenomena range from 200-2,000 km across, while meso-beta phenomena range from 20–200 km across. The microscale is the smallest of the scales, with a size under two kilometers. These horizontal dimensions are not rigid divisions but instead reflect typical sizes of phenomena having certain dynamic characteristics, for example, a system does not necessarily transition from meso-alpha to synoptic scale when its horizontal extent grows from 2,000 to 2,001 km. The Norwegian Cyclone Model is an idealized model of cold-core cyclonic storms developed by Norwegian meteorologists during the First World War. A preexisting frontal boundary, as defined in surface analysis, is required for the development of a mid-latitude cyclone. However, enhanced along-frontal stretching rates in the troposphere can suppress the growth of extratropical cyclones. Cyclogenesis can only occur when temperature decreases polewards, and pressure perturbation lines tilt westward with height, cyclogenesis is most likely to occur in regions of cyclonic vorticity advection, downstream of a strong westerly jet. The combination of vorticity advection and thermal advection created by the temperature gradient, if the temperature gradient is strong enough, temperature advection will increase, driving more vertical motion. This increases the strength of the system. Shearwise updrafts are the most important factor in determining cyclonic growth and strength, the surface low could have a variety of causes for forming. Topography can force a surface low when dense low-level high pressure ridges in east of a north-south mountain barrier
6.
Meteorology
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Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not occur until the 18th century, the 19th century saw modest progress in the field after weather observation networks were formed across broad regions. Prior attempts at prediction of weather depended on historical data, Meteorological phenomena are observable weather events that are explained by the science of meteorology. Different spatial scales are used to describe and predict weather on local, regional, Meteorology, climatology, atmospheric physics, and atmospheric chemistry are sub-disciplines of the atmospheric sciences. Meteorology and hydrology compose the interdisciplinary field of hydrometeorology, the interactions between Earths atmosphere and its oceans are part of a coupled ocean-atmosphere system. Meteorology has application in diverse fields such as the military, energy production, transport, agriculture. The word meteorology is from Greek μετέωρος metéōros lofty, high and -λογία -logia -logy, varāhamihiras classical work Brihatsamhita, written about 500 AD, provides clear evidence that a deep knowledge of atmospheric processes existed even in those times. In 350 BC, Aristotle wrote Meteorology, Aristotle is considered the founder of meteorology. One of the most impressive achievements described in the Meteorology is the description of what is now known as the hydrologic cycle and they are all called swooping bolts because they swoop down upon the Earth. Lightning is sometimes smoky, and is then called smoldering lightning, sometimes it darts quickly along, at other times, it travels in crooked lines, and is called forked lightning. When it swoops down upon some object it is called swooping lightning, the Greek scientist Theophrastus compiled a book on weather forecasting, called the Book of Signs. The work of Theophrastus remained a dominant influence in the study of weather, in 25 AD, Pomponius Mela, a geographer for the Roman Empire, formalized the climatic zone system. According to Toufic Fahd, around the 9th century, Al-Dinawari wrote the Kitab al-Nabat, ptolemy wrote on the atmospheric refraction of light in the context of astronomical observations. St. Roger Bacon was the first to calculate the size of the rainbow. He stated that a rainbow summit can not appear higher than 42 degrees above the horizon, in the late 13th century and early 14th century, Kamāl al-Dīn al-Fārisī and Theodoric of Freiberg were the first to give the correct explanations for the primary rainbow phenomenon. Theoderic went further and also explained the secondary rainbow, in 1716, Edmund Halley suggested that aurorae are caused by magnetic effluvia moving along the Earths magnetic field lines. In 1441, King Sejongs son, Prince Munjong, invented the first standardized rain gauge and these were sent throughout the Joseon Dynasty of Korea as an official tool to assess land taxes based upon a farmers potential harvest. In 1450, Leone Battista Alberti developed a swinging-plate anemometer, and was known as the first anemometer, in 1607, Galileo Galilei constructed a thermoscope
7.
Rossby wave
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Rossby waves, also known as planetary waves, are a natural phenomenon in the atmosphere and oceans of planets that largely owe their properties to rotation of the planet. Rossby waves are a subset of inertial waves, atmospheric Rossby waves on Earth are giant meanders in high-altitude winds that have a major influence on weather. These waves are associated with systems and the jet stream. Oceanic Rossby waves move along the thermocline, the boundary between the upper layer and the cold deeper part of the ocean. Atmospheric Rossby waves result from the conservation of vorticity and are influenced by the Coriolis force. A fluid, on the Earth, that moves toward the pole will deviate toward the east, the deviations are caused by the Coriolis force and conservation of potential vorticity which leads to changes of relative vorticity. This is analogous to conservation of momentum in mechanics. In planetary atmospheres, including Earth, Rossby waves are due to the variation in the Coriolis effect with latitude, carl-Gustaf Arvid Rossby first identified such waves in the Earths atmosphere in 1939 and went on to explain their motion. One can identify a terrestrial Rossby wave as its velocity, marked by its wave crest. However, the set of Rossby waves may appear to move in either direction with what is known as its group velocity. In general, shorter waves have a group velocity and long waves a westward group velocity. The terms barotropic and baroclinic are used to distinguish the structure of Rossby waves. Barotropic Rossby waves do not vary in the vertical, and have the fastest propagation speeds, the baroclinic wave modes, on the other hand, do vary in the vertical. They are also slower, with speeds of only a few centimeters per second or less, most investigations of Rossby waves has been done on those in Earths atmosphere. Rossby waves in the Earths atmosphere are easy to observe as large-scale meanders of the jet stream, the action of Rossby waves partially explains why eastern continental edges, such as the Northeast United States and Eastern Canada, are colder than Western Europe at the same latitudes. Deep convection to the troposphere is enhanced over very warm sea surfaces in the tropics and this tropical forcing generates atmospheric Rossby waves that have a poleward and eastward migration. Poleward-propagating Rossby waves explain many of the observed statistical connections between low- and high-latitude climates, one such phenomenon is sudden stratospheric warming. Poleward-propagating Rossby waves are an important and unambiguous part of the variability in the Northern Hemisphere, similar mechanisms apply in the Southern Hemisphere and partly explain the strong variability in the Amundsen Sea region of Antarctica
8.
Westerlies
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The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the areas in the horse latitudes and tend towards the poles. Tropical cyclones which cross the ridge axis into the westerlies recurve due to the increased westerly flow. The winds are predominantly from the southwest in the Northern Hemisphere, the strongest westerly winds in the middle latitudes can come in the roaring forties, between 40 and 50 degrees latitude. The westerlies play an important role in carrying the warm, equatorial waters and winds to the coasts of continents. If the Earth were a planet, solar heating would cause winds across the mid-latitudes to blow in a poleward direction. This is why winds across the Northern Hemisphere tend to blow from the southwest, when pressures are lower over the poles, the strength of the westerlies increases, which has the effect of warming the mid-latitudes. This occurs when the Arctic oscillation is positive, and during low pressure near the poles is stronger than it would be during the summer. When it is negative and pressures are higher over the poles, the flow is more meridional, blowing from the direction of the pole towards the equator, throughout the year, the westerlies vary in strength with the polar cyclone. As the cyclone reaches its maximum intensity in winter, the increase in strength. As the cyclone reaches its weakest intensity in summer, the Westerlies weaken, an example of the impact of the westerlies is when dust plumes, originating in the Gobi desert combine with pollutants and spread large distances downwind, or eastward, into North America. The westerlies can be strong, especially in the Southern Hemisphere. The currents in the Northern Hemisphere are weaker than those in the Southern Hemisphere due to the differences in strength between the westerlies of each hemisphere. The process of western intensification causes currents on the boundary of an ocean basin to be stronger than those on the eastern boundary of an ocean. These western ocean currents transport warm, tropical water polewards toward the polar regions, ships crossing both oceans have taken advantage of the ocean currents for centuries. The Antarctic Circumpolar Current, or the West Wind Drift, is a current that flows from west to east around Antarctica. The ACC is the dominant circulation feature of the Southern Ocean and, at approximately 125 Sverdrups, the largest ocean current. The Kuroshio is a western boundary current in the western north Pacific Ocean, similar to the Gulf Stream
9.
Trough (meteorology)
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A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts. Unlike fronts, there is not a symbol for a trough on a weather chart. The weather charts in countries or regions mark troughs by a line. In the United States, a trough may be marked as a dashed line. In the UK, Hong Kong and Fiji, it is represented by a line extended from a low pressure center or between two low pressure centers, in Macau and Australia, it is a dashed line. If they are not marked, troughs may still be identified as an extension of isobars away from a low pressure center, sometimes the region between two high pressure centers may assume the character of a trough when there is a detectable wind shift noted at the surface. In the absence of a shift, the region is designated a col. If a trough forms in the mid-latitudes, a difference between two sides of the trough usually exists in the form of a weather front. A weather front is less convective than a trough in the tropics or subtropics. Sometimes collapsed frontal systems will degenerate into troughs, convective cells may develop in the vicinity of troughs and give birth to a tropical cyclone. Some tropical or subtropical regions such as the Philippines or south China are greatly affected by convection cells along a trough, in the mid-latitude westerlies, troughs and ridges often alternate, especially when upper-level winds are in a high-amplitude pattern. Tropical waves are a type of trough in easterly currents, a cyclonic northward deflection of the trade winds, troughs may be at the surface, or aloft, or both under various conditions. Most troughs bring clouds, showers, and a wind shift and this results from convergence or squeezing which forces lifting of moist air behind the trough line. In addition to standard troughs, some may be described further with a term indicating a specific or a set of characteristics. An inverted trough is a trough which is oriented opposite to most troughs of the mid-latitudes. Most inverted troughs are tropical waves, the situation is opposite in the Southern Hemisphere. Inverted troughs in both hemispheres move to the west from the east, while mid-latitude troughs generally move with the westerlies toward the east
10.
Wavelength
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In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the waves shape repeats, and thus the inverse of the spatial frequency. Wavelength is commonly designated by the Greek letter lambda, the concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also applied to modulated waves. Wavelength depends on the medium that a wave travels through, examples of wave-like phenomena are sound waves, light, water waves and periodic electrical signals in a conductor. A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric, water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary, wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves. For example, in waves over deep water a particle near the waters surface moves in a circle of the same diameter as the wave height. The range of wavelengths or frequencies for wave phenomena is called a spectrum, the name originated with the visible light spectrum but now can be applied to the entire electromagnetic spectrum as well as to a sound spectrum or vibration spectrum. In linear media, any pattern can be described in terms of the independent propagation of sinusoidal components. The wavelength λ of a sinusoidal waveform traveling at constant speed v is given by λ = v f, in a dispersive medium, the phase speed itself depends upon the frequency of the wave, making the relationship between wavelength and frequency nonlinear. In the case of electromagnetic radiation—such as light—in free space, the speed is the speed of light. Thus the wavelength of a 100 MHz electromagnetic wave is about, the wavelength of visible light ranges from deep red, roughly 700 nm, to violet, roughly 400 nm. For sound waves in air, the speed of sound is 343 m/s, the wavelengths of sound frequencies audible to the human ear are thus between approximately 17 m and 17 mm, respectively. Note that the wavelengths in audible sound are much longer than those in visible light, a standing wave is an undulatory motion that stays in one place. A sinusoidal standing wave includes stationary points of no motion, called nodes, the upper figure shows three standing waves in a box. The walls of the box are considered to require the wave to have nodes at the walls of the box determining which wavelengths are allowed, the stationary wave can be viewed as the sum of two traveling sinusoidal waves of oppositely directed velocities. Consequently, wavelength, period, and wave velocity are related just as for a traveling wave, for example, the speed of light can be determined from observation of standing waves in a metal box containing an ideal vacuum. In that case, the k, the magnitude of k, is still in the same relationship with wavelength as shown above
11.
Shortwave (meteorology)
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A shortwave or shortwave trough is an embedded kink in the trough / ridge pattern. Its length scale is smaller than that of longwaves, which are responsible for the largest scale weather systems. Shortwaves may be contained within or found ahead of longwaves and range from the mesoscale to the synoptic scale, shortwaves are most frequently caused by either a cold pool or an upper level front. Shortwaves are often associated with warm air advection or cold air advection, due to the way they move the air around them and the way air moves away from them, shortwaves produce positive curvature vorticity and positive shear vorticity, respectively. Ahead of a shortwave there is large-scale lift due to divergence from positive vorticity advection, in a capped environment, the lift generated by a shortwave may cool the inversion layer as a result of the rapid expansion of the air, allowing for deep, moist convection
12.
Atmosphere
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An atmosphere is a layer of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is likely to be retained if the gravity it is subject to is high. The atmosphere of Earth is mostly composed of nitrogen, oxygen, argon with carbon dioxide, the atmosphere helps protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. Its current composition is the product of billions of years of modification of the paleoatmosphere by living organisms. The term stellar atmosphere describes the region of a star. Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere, Atmospheric pressure is the force per unit area that is applied perpendicularly to a surface by the surrounding gas. It is determined by a gravitational force in combination with the total mass of a column of gas above a location. On Earth, units of air pressure are based on the recognized standard atmosphere. It is measured with a barometer, the pressure of an atmospheric gas decreases with altitude due to the diminishing mass of gas above. The height at which the pressure from an atmosphere declines by a factor of e is called the height and is denoted by H. For such an atmosphere, the pressure declines exponentially with increasing altitude. However, atmospheres are not uniform in temperature, so the determination of the atmospheric pressure at any particular altitude is more complex. Surface gravity, the force that holds down an atmosphere, differs significantly among the planets, for example, the large gravitational force of the giant planet Jupiter is able to retain light gases such as hydrogen and helium that escape from objects with lower gravity. Thus, the distant and cold Titan, Triton, and Pluto are able to retain their atmospheres despite their relatively low gravities, rogue planets, theoretically, may also retain thick atmospheres. Since a collection of gas molecules may be moving at a range of velocities. Lighter molecules move faster than ones with the same thermal kinetic energy. It is thought that Venus and Mars may have lost much of their water when, after being photo dissociated into hydrogen and oxygen by solar ultraviolet, Earths magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the polar regions due to auroral activity
13.
Thermal low
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Over land, intense, rapid solar heating of the land surface results in heating of the lowest layers of the atmosphere via reradiated energy in the infrared spectrum. The resulting hotter air is less dense than surrounding cooler air and this, combined with the rising of the hot air, results in the formation of a low pressure area. Elevated areas can enhance the strength of the low as they warm more quickly than the atmosphere which surrounds them at the same altitude. Over the water, instability lows form during the winter when the air overlying the land is colder than the water body. Thermal lows tend to have weak circulations, and can extend to 3,100 metres in height, thermal lows over the western and southern portions of North America, northern Africa, and southeast Asia are strong enough to lead to summer monsoon conditions. Development of thermal lows inland of the lead to the development of sea breezes. Sea breezes combined with rugged topography near the coast can encourage poor air quality, in deserts, lack of ground and plant moisture that would normally provide evaporative cooling can lead to intense, rapid solar heating of the lower layers of air. The hot air is less dense than surrounding cooler air and this, combined with the rising of the hot air, results in a low pressure area called a thermal low. During the cold season, warm water bodies such as the Great Lakes can induce an instability low. Thermal lows which develop near sea level can build in height during the season, or summer, to the elevation of the 700 hPa pressure surface. Heat lows normally are stationary and have a weak cyclonic circulation, as they are strongest at the surface and warm near their center, and weaker aloft where the air is more stable, the thermal low is considered warm core. The formation of the heat low over northern Africa leads to a westerly jet stream from June into October. Monsoons are caused by the amplitude of the seasonal cycle of land temperature compared to that of nearby oceans. Additionally, the heat capacity of liquid water is significantly higher than that of most materials that make up land. The hot air over the land tends to rise, creating an area of low pressure and this creates a steady wind blowing toward the land, bringing the moist near-surface air over the oceans with it. Similar rainfall is caused by the moist ocean air being lifted upwards by mountains, surface heating, convergence at the surface, divergence aloft, however the lifting occurs, the air cools due expansion in lower pressure, which in turn produces condensation. In winter, the land cools off quickly, but the keeps the heat longer due to its higher specific heat. The hot air over the ocean rises, creating a low pressure area, the sea is warmed by the sun to a greater depth than the land due to its greater specific heat
14.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
15.
Continent
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A continent is one of several very large landmasses on Earth. Generally identified by convention rather than any strict criteria, up to seven regions are regarded as continents. Ordered from largest in size to smallest, they are, Asia, Africa, North America, South America, Antarctica, Europe, in geology, areas of continental crust include regions covered with water. Islands are frequently grouped with a continent to divide all the worlds land into geopolitical regions. Under this scheme, most of the countries and territories in the Pacific Ocean are grouped together with the continent of Australia to form a geopolitical region called Oceania. By convention, continents are understood to be large, continuous, discrete masses of land, many of the seven most commonly recognized continents identified by convention are not discrete landmasses separated completely by water. Earths major landmasses all have coasts on a single, continuous World Ocean, the most restricted meaning of continent is that of a continuous area of land or mainland, with the coastline and any land boundaries forming the edge of the continent. From this perspective the edge of the shelf is the true edge of the continent. In this sense the islands of Great Britain and Ireland are part of Europe, while Australia, as a cultural construct, the concept of a continent may go beyond the continental shelf to include oceanic islands and continental fragments. In this way, Iceland is considered part of Europe and Madagascar part of Africa, extrapolating the concept to its extreme, some geographers group the Australasian continental plate with other islands in the Pacific into one continent called Oceania. This divides the land surface of Earth into continents or quasi-continents. The ideal criterion that each continent be a discrete landmass is commonly relaxed due to historical conventions, of the seven most globally recognized continents, only Antarctica and Australia are completely separated from other continents by ocean. Several continents are defined not as absolutely distinct bodies but as more or less discrete masses of land, Asia and Africa are joined by the Isthmus of Suez, and North and South America by the Isthmus of Panama. In both cases, there is no separation of these landmasses by water. Both these isthmuses are very narrow compared to the bulk off the landmasses they unite, North America and South America are treated as separate continents in the seven-continent model. However, they may also be viewed as a continent known as America or the Americas. This viewpoint was common in the United States until World War II and this remains the more common vision in Latin American countries, Spain, Portugal, France, Italy and Greece, where they are taught as a single continent. The criterion of a landmass is completely disregarded if the continuous landmass of Eurasia is classified as two separate continents, Europe and Asia
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Monsoon
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Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is sometimes used for locally heavy but short-term rains. The major monsoon systems of the world consist of the West African and Asia-Australian monsoons, the inclusion of the North and South American monsoons with incomplete wind reversal has been debated. The south-west monsoon winds are called Nairutya Maarut in India, the English monsoon came from Portuguese monção, ultimately from Arabic mawsim and/or Hindi mausam, perhaps partly via early modern Dutch monsun. Strengthening of the Asian monsoon has been linked to the uplift of the Tibetan Plateau after the collision of the Indian sub-continent and Asia around 50 million years ago. Because of studies of records from the Arabian Sea and that of the wind-blown dust in the Loess Plateau of China, testing of this hypothesis awaits deep ocean sampling by the Integrated Ocean Drilling Program. The monsoon has varied significantly in strength since this time, largely linked to climate change. A study of marine plankton suggested that the Indian Monsoon strengthened around 5 million years ago, then, during ice periods, the sea level fell and the Indonesian Seaway closed. When this happened, cold waters in the Pacific were impeded from flowing into the Indian Ocean and it is believed that the resulting increase in sea surface temperatures in the Indian Ocean increased the intensity of monsoons. Five episodes during the Quaternary at 2.22 Ma,1.83 Ma,0.68 Ma,0.45 Ma and 0.04 Ma were identified which showed a weakening of Leeuwin Current. The weakening of the LC would have an effect on the sea surface temperature field in the Indian Ocean, thus these five intervals could probably be those of considerable lowering of SST in the Indian Ocean and would have influenced Indian monsoon intensity. The impact of monsoon on the weather is different from place to place. In some places there is just a likelihood of having a more or less rain. In other places, quasi semi-deserts are turned into green grasslands where all sorts of plants. The Indian Monsoon turns large parts of India from a kind of semi-desert into green lands, see photos only taken 3 months apart in the Western Ghats. In places like this it is crucial for farmers to have the right timing for putting the seeds on the fields, Monsoons are large-scale sea breezes which occur when the temperature on land is significantly warmer or cooler than the temperature of the ocean. These temperature imbalances happen because oceans and land absorb heat in different ways, in contrast, dirt, sand, and rocks have lower heat capacities, and they can only transmit heat into the earth by conduction and not by convection. Therefore, bodies of water stay at an even temperature
17.
Intertropical Convergence Zone
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The Intertropical Convergence Zone, known by sailors as the doldrums, is the area encircling the earth near the equator where the northeast and southeast trade winds converge. When it lies near the equator, it is called the near-equatorial trough, where the ITCZ is drawn into and merges with a monsoonal circulation, it is sometimes referred to as a monsoon trough, a usage more common in Australia and parts of Asia. In the seamens speech the zone is referred to as the doldrums because of its weather patterns with stagnant calms. The ITCZ appears as a band of clouds, usually thunderstorms, in the Northern Hemisphere, the trade winds move in a southwestern direction from the northeast, while in the Southern Hemisphere, they move northwestward from the southeast. When the ITCZ is positioned north or south of the equator, for instance, when the ITCZ is situated north of the equator, the southeast trade wind changes to a southwest wind as it crosses the equator. The ITCZ is formed by vertical motion largely appearing as convective activity of thunderstorms driven by heating, which effectively draw air in. The ITCZ is effectively a tracer of the branch of the Hadley cell. The dry descending branch is the horse latitudes, the location of the intertropical convergence zone varies over time with the seasons. Over land, it moves back and forth across the following the suns zenith point. Over the oceans, where the convergence zone is better defined, sometimes, a double ITCZ forms, with one located north and another south of the equator, one of which is usually stronger than the other. When this occurs, a ridge of high pressure forms between the two convergence zones. The South Pacific convergence zone is a reverse-oriented, or west-northwest to east-southeast aligned and it lies just south of the equator during the Southern Hemisphere warm season, but can be more extratropical in nature, especially east of the International Date Line. It is considered the largest and most important piece of the ITCZ, longer term changes in the intertropical convergence zone can result in severe droughts or flooding in nearby areas. In some cases, the ITCZ may become narrow, especially when it moves away from the equator, there appears to be a 15- to 25-day cycle in thunderstorm activity along the ITCZ, which is roughly half the wavelength of the Madden–Julian oscillation. Within the ITCZ the average winds are slight, unlike the north and south of the equator where the trade winds feed. Early sailors named this belt of calm the doldrums because of the inactivity, to find oneself becalmed in this region in a hot and muggy climate could mean death in an era when wind was the only effective way to propel ships across the ocean. Even today leisure and competitive sailors attempt to cross the zone as quickly as possible as the erratic weather and wind patterns may cause unexpected delays. Tropical cyclogenesis depends upon low-level vorticity as one of its six requirements, surges of higher pressure from high latitudes can enhance tropical disturbances along its axis
18.
Monsoon trough
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Westerly monsoon winds lie in its equatorward portion while easterly trade winds exist poleward of the trough. Right along its axis, heavy rains can be found which usher in the peak of a locations respective rainy season, as it passes poleward of a location, hot and dry conditions develop. The monsoon trough plays a role in creating many of the worlds rainforests, the term monsoon trough is most commonly used in monsoonal regions of the Western Pacific such as Asia and Australia. The migration of the ITCZ/monsoon trough into a landmass heralds the beginning of the rainy season during summer months. Depressions and tropical cyclones form in the vicinity of the monsoon trough. Monsoon troughing in the western Pacific reaches its zenith in latitude during the summer when the wintertime surface ridge in the opposite hemisphere is the strongest. It can reach as far as the 40th parallel in East Asia during August and its poleward progression is accelerated by the onset of the summer monsoon which is characterized by the development of lower air pressure over the warmest part of the various continents. In the Southern Hemisphere, the monsoon trough associated with the Australian monsoon reaches its most southerly latitude in February, increases in the relative vorticity, or spin, with the monsoon trough are normally a product of increased wind convergence within the convergence zone of the monsoon trough. Wind surges can lead to increase in convergence. A strengthening or equatorward movement in the ridge can cause a strengthening of a monsoon trough as a wind surge moves towards the location of the monsoon trough. A key way of detecting whether a wind surge has reached a trough is the formation of a burst of thunderstorms within the monsoon trough. If a circulation forms within the trough, it is able to compete with the neighboring thermal low over the continent. Such a circulation which is broad in nature within a trough is known as a monsoon depression. In the Northern Hemisphere, monsoon depressions are generally asymmetric, light and variable winds cover a large area near their center, while bands of showers and thunderstorms develop within their area of circulation. Even though these systems can develop over land, the portions of monsoon depressions are similar to tropical cyclones. In India, for example,6 to 7 monsoon depressions move across the country yearly, monsoon depressions are efficient rainfall producers, and can cause a years worth of rainfall when they move through drier areas such as the outback of Australia. Its abrupt movement to the north between May and June is coincident with the beginning of the regime and rainy seasons across South. This convergence zone has been linked to prolonged heavy rain events in the Yangtze river as well as northern China and its presence has also been linked to the peak of the rainy season in locations within Australia
19.
Tropical cyclone
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Depending on its location and strength, a tropical cyclone is referred to by names such as hurricane, typhoon /taɪˈfuːn/, tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy through the evaporation of water from the ocean surface and this energy source differs from that of mid-latitude cyclonic storms, such as noreasters and European windstorms, which are fueled primarily by horizontal temperature contrasts. The strong rotating winds of a tropical cyclone are a result of the conservation of momentum imparted by the Earths rotation as air flows inwards toward the axis of rotation. As a result, they form within 5° of the equator. Tropical cyclones are typically between 100 and 2,000 km in diameter, Tropical refers to the geographical origin of these systems, which form almost exclusively over tropical seas. Cyclone refers to their nature, with wind blowing counterclockwise in the Northern Hemisphere. The opposite direction of circulation is due to the Coriolis effect, in addition to strong winds and rain, tropical cyclones are capable of generating high waves, damaging storm surge, and tornadoes. They typically weaken rapidly over land where they are cut off from their energy source. For this reason, coastal regions are vulnerable to damage from a tropical cyclone as compared to inland regions. Heavy rains, however, can cause significant flooding inland, though their effects on human populations are often devastating, tropical cyclones can relieve drought conditions. They also carry heat away from the tropics and transport it toward temperate latitudes. Tropical cyclones are areas of low pressure in the troposphere. On Earth, the pressures recorded at the centers of tropical cyclones are among the lowest ever observed at sea level, the environment near the center of tropical cyclones is warmer than the surroundings at all altitudes, thus they are characterized as warm core systems. The near-surface wind field of a cyclone is characterized by air rotating rapidly around a center of circulation while also flowing radially inwards. At the outer edge of the storm, air may be nearly calm, however, due to the Earths rotation, as air flows radially inward, it begins to rotate cyclonically in order to conserve angular momentum. At an inner radius, air begins to ascend to the top of the troposphere and this radius is typically coincident with the inner radius of the eyewall, and has the strongest near-surface winds of the storm, consequently, it is known as the radius of maximum winds. Once aloft, air flows away from the center, producing a shield of cirrus clouds
20.
Cloud cover
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Cloud cover refers to the fraction of the sky obscured by clouds when observed from a particular location. Okta is the unit of measurement of the cloud cover. The cloud cover is correlated to the duration as the least cloudy locales are the sunniest ones while the cloudiest areas are the least sunny places. The global cloud cover averages around 0.68 when analysing clouds with optical depth larger than 0.1 and this value is lower when considering clouds with an optical depth larger than 2 and higher when counting subvisible cirrus clouds. Clouds play multiple roles in the climate system. In particular, being bright objects in the part of the solar spectrum, they efficiently reflect light to space. Cloud cover thus plays an important role in the balance of the atmosphere. Cloud cover values only vary by 0.03 from year to year, whereas the local, most data sets agree on the fact that the land is covered by 0. 10-0.15 less cloud than the oceans. Lastly, there is a variation in the cloud cover. Almost the same variation is found 20°S, on the other hand, in the storm regions of the Southern Hemisphere midlatitudes were found to have with 0. 15-0.25 more cloudiness than the global mean at 60°S. On average, about 52% of Earth is cloud-covered at any moment, some regions are almost always cloudy such as the Amazon Rainforest and some others are almost always clear such as the Sahara Desert
21.
Diurnal temperature variation
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Atmospheric temperature range is the numerical difference between the minimum and maximum values of temperature observed in a given location during a period of time or the average. The variation in temperature occurs from the highs of the day to the cool of nights is called diurnal temperature variation. Average yearly temperature is 22.4 degrees Celsius, ranging from a minimum of 12.2 degrees to a maximum of 29.9 degrees. The average temperature range is 11.4 degrees, variability along the year is small. It is easy to see in the graph another typical phenomenon of temperature ranges, in Campinas, for example, the daily temperature range in July may vary between typically 10 and 24 degrees Celsius, while in January, it may range between 20 and 30 degrees Celsius. The effect of latitude, tropical climate, constant gentle wind and sea-side locations show smaller average temperature ranges, smaller variations of temperature, average maximum yearly temperature is 28.7 degrees Celsius and average minimum is 21.9. The average temperature range is 5.7 degrees only, temperature variation along the year in Aracaju is very damped. Most of the places with these characteristics are located in the transition between temperate and tropical climates, approximately around the tropics, particularly in the Southern hemisphere, the minimum temperature at night does not occur on the ground but few tens of centimeters above the ground. The phenomenon is attributed to the interaction of radiation effects on atmospheric aerosols
22.
Sunlight
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Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is filtered through Earths atmosphere, and is obvious as daylight when the Sun is above the horizon, when the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When it is blocked by clouds or reflects off other objects, the World Meteorological Organization uses the term sunshine duration to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter. Other sources indicate an Average over the earth of 164 Watts per square meter over a 24 hour day. The ultraviolet radiation in sunlight has both positive and negative effects, as it is both a principal source of vitamin D3 and a mutagen. Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun. A photon starting at the center of the Sun and changing every time it encounters a charged particle would take between 10,000 and 170,000 years to get to the surface. Researchers may record sunlight using a sunshine recorder, pyranometer, or pyrheliometer, to calculate the amount of sunlight reaching the ground, both Earths elliptical orbit and the attenuation by Earths atmosphere have to be taken into account. In this formula dn–3 is used, because in modern times Earths perihelion, the closest approach to the Sun and, therefore, the value of 0.033412 is determined knowing that the ratio between the perihelion squared and the aphelion squared should be approximately 0.935338. The solar illuminance constant, is equal to 128×103 lx, the atmospheric extinction brings the number of lux down to around 100000. The total amount of energy received at ground level from the Sun at the zenith depends on the distance to the Sun and it is about 3. 3% higher than average in January and 3. 3% lower in July. In terms of energy, sunlight at Earths surface is around 52 to 55 percent infrared,42 to 43 percent visible, and 3 to 5 percent ultraviolet. At the top of the atmosphere, sunlight is about 30% more intense, having about 8% ultraviolet, direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux. This is higher than the efficacy of most artificial lighting, which means using sunlight for illumination heats up a less than using most forms of artificial lighting. Multiplying the figure of 1050 watts per square metre by 93 lumens per watt indicates that bright sunlight provides an illuminance of approximately 98000 lux on a surface at sea level. The illumination of a surface will be considerably less than this if the Sun is not very high in the sky. Averaged over a day, the highest amount of sunlight on a horizontal surface occurs in January at the South Pole, dividing the irradiance of 1050 W/m2 by the size of the suns disk in steradians gives an average radiance of 15.4 MW per square metre per steradian. Multiplying this by π gives a limit to the irradiance which can be focused on a surface using mirrors,48.5 MW/m2
23.
Solar radiation
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Solar irradiance is the power per unit area received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Irradiance may be measured in space or at the Earths surface after atmospheric absorption and it is measured perpendicular to the incoming sunlight. Total solar irradiance, is a measure of the power over all wavelengths per unit area incident on the Earths upper atmosphere. The solar constant is a measure of mean TSI at a distance of one astronomical Unit. Irradiance is a function of distance from the Sun, the solar cycle, Irradiance on Earth is also measured perpendicular to the incoming sunlight. Insolation is the received on Earth per unit area on a horizontal surface. It depends on the height of the Sun above the horizon, the solar irradiance integrated over time is called solar irradiation, solar exposure or insolation. However, insolation is often used interchangeably with irradiance in practice, the SI unit of irradiance is watt per square meter. An alternate unit of measure is the Langley per unit time, the solar energy industry uses watt-hour per square metre per unit time, the relation to the SI unit is thus 1 kW/m2 =24 kWh/m2/day =8760 kWh/m2/year. Irradiance can also be expressed in Suns, where one Sun equals 1000 W/m2 at the point of arrival, part of the radiation reaching an object is absorbed and the remainder reflected. Usually the absorbed radiation is converted to energy, increasing the objects temperature. Manmade or natural systems, however, can convert part of the radiation into another form such as electricity or chemical bonds. The proportion of reflected radiation is the objects reflectivity or albedo, insolation onto a surface is largest when the surface directly faces the sun. As the angle between the surface and the Sun moves from normal, the insolation is reduced in proportion to the angles cosine, see effect of sun angle on climate. In the figure, the angle shown is between the ground and the rather than between the vertical direction and the sunbeam, hence the sine rather than the cosine is appropriate. A sunbeam one mile wide arrives from directly overhead, and another at a 30° angle to the horizontal, the sine of a 30° angle is 1/2, whereas the sine of a 90° angle is 1. Therefore, the angled sunbeam spreads the light over twice the area, consequently, half as much light falls on each square mile. This projection effect is the reason why Earths polar regions are much colder than equatorial regions
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Temperature
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A temperature is an objective comparative measurement of hot or cold. It is measured by a thermometer, several scales and units exist for measuring temperature, the most common being Celsius, Fahrenheit, and, especially in science, Kelvin. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, the kinetic theory offers a valuable but limited account of the behavior of the materials of macroscopic bodies, especially of fluids. Temperature is important in all fields of science including physics, geology, chemistry, atmospheric sciences, medicine. The Celsius scale is used for temperature measurements in most of the world. Because of the 100 degree interval, it is called a centigrade scale.15, the United States commonly uses the Fahrenheit scale, on which water freezes at 32°F and boils at 212°F at sea-level atmospheric pressure. Many scientific measurements use the Kelvin temperature scale, named in honor of the Scottish physicist who first defined it and it is a thermodynamic or absolute temperature scale. Its zero point, 0K, is defined to coincide with the coldest physically-possible temperature and its degrees are defined through thermodynamics. The temperature of zero occurs at 0K = −273. 15°C. For historical reasons, the triple point temperature of water is fixed at 273.16 units of the measurement increment, Temperature is one of the principal quantities in the study of thermodynamics. There is a variety of kinds of temperature scale and it may be convenient to classify them as empirically and theoretically based. Empirical temperature scales are historically older, while theoretically based scales arose in the middle of the nineteenth century, empirically based temperature scales rely directly on measurements of simple physical properties of materials. For example, the length of a column of mercury, confined in a capillary tube, is dependent largely on temperature. Such scales are only within convenient ranges of temperature. For example, above the point of mercury, a mercury-in-glass thermometer is impracticable. A material is of no use as a thermometer near one of its phase-change temperatures, in spite of these restrictions, most generally used practical thermometers are of the empirically based kind. Especially, it was used for calorimetry, which contributed greatly to the discovery of thermodynamics, nevertheless, empirical thermometry has serious drawbacks when judged as a basis for theoretical physics. Theoretically based temperature scales are based directly on theoretical arguments, especially those of thermodynamics, kinetic theory and they rely on theoretical properties of idealized devices and materials
25.
Outgoing longwave radiation
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Outgoing Longwave Radiation is the energy radiating from the Earth as infrared radiation at low energy to Space. OLR is electromagnetic radiation emitted from Earth and its atmosphere out to space in the form of thermal radiation, the flux of energy transported by outgoing longwave radiation is measured in W/m². Over 99% of outgoing longwave radiation has wavelengths between 4 µm and 100 µm, in the infrared part of the electromagnetic spectrum. Contributions with wavelengths larger than 40 µm are small, therefore often only wavelengths up to 50 µm are considered, radiative cooling by outgoing longwave radiation is the primary way the Earth System loses energy. The balance between loss and the energy gained by radiative heating from incoming solar shortwave radiation determines global heating or cooling of the Earth system. Local differences between radiative heating and cooling provide the energy that drives atmospheric dynamics, OLR is a critical component of the Earths energy budget, and represents the total radiation going to space emitted by the atmosphere. Earths radiation balance is quite closely achieved since the OLR very nearly equals the Shortwave Absorbed Radiation received at high energy from the sun, thus, the Earths average temperature is very nearly stable. The OLR is affected by clouds and dust in the atmosphere, some of this radiation is directed back towards the Earth, increasing the average temperature of the Earths surface. The OLR is dependent on the temperature of the radiating body and it is affected by the Earths skin temperature, skin surface emissivity, atmospheric temperature, water vapor profile, and cloud cover. Longwave radiation typically refers to radiation in the region from 3 to 100 microns. In the Earth’s climate system, longwave radiation involves processes of absorption, scattering, and emissions from atmospheric gases, aerosols, clouds, outgoing longwave radiation has been monitored globally since 1975 by a number of successful and valuable satellite missions. Downwelling longwave radiation at the surface is measured by Pyrgeometer. Calculations of these solve the radiative transfer equations that describe radiation in the atmosphere. Usually the solution is done numerically by an Atmospheric radiative transfer code adapted to the specific problem
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Wind
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Wind is the flow of gases on a large scale. On the surface of the Earth, wind consists of the movement of air. Winds are commonly classified by their scale, their speed, the types of forces that cause them, the regions in which they occur. The strongest observed winds on a planet in the Solar System occur on Neptune, Winds have various aspects, an important one being its velocity, another the density of the gas involved, another its energy content or wind energy. In meteorology, winds are referred to according to their strength. Short bursts of high speed wind are termed gusts, strong winds of intermediate duration are termed squalls. Long-duration winds have various names associated with their strength, such as breeze, gale, storm. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet, within the tropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds, in areas that have variable terrain, mountain, Wind powers the voyages of sailing ships across Earths oceans. Hot air balloons use the wind to take trips, and powered flight uses it to increase lift. Areas of wind caused by various weather phenomena can lead to dangerous situations for aircraft. When winds become strong, trees and man-made structures are damaged or destroyed, Winds can shape landforms, via a variety of aeolian processes such as the formation of fertile soils, such as loess, and by erosion. Wind also affects the spread of wildfires, Winds can disperse seeds from various plants, enabling the survival and dispersal of those plant species, as well as flying insect populations. When combined with temperatures, wind has a negative impact on livestock. Wind affects animals food stores, as well as their hunting, Wind is caused by differences in the atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the pressure area. On a rotating planet, air will also be deflected by the Coriolis effect, globally, the two major driving factors of large-scale wind patterns are the differential heating between the equator and the poles and the rotation of the planet. Outside the tropics and aloft from frictional effects of the surface, near the Earths surface, friction causes the wind to be slower than it would be otherwise
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Tibetan Plateau
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It stretches approximately 1,000 kilometres north to south and 2,500 kilometres east to west. Sometimes termed the Third Pole, the Tibetan Plateau contains the headwaters of the basins of most of the streams in surrounding regions. Its tens of thousands of glaciers and other geographical and ecological features serve as a water tower storing water, the impact of global warming on the Tibetan Plateau is of intense scientific interest. The Tibetan Plateau is surrounded by mountain ranges. In the west the curve of the rugged Karakoram range of northern Kashmir embraces the plateau, the Indus River originates in the western Tibetan Plateau in the vicinity of Lake Mansarovar. The Tibetan Plateau is bounded in the north by an escarpment where the altitude drops from around 5,000 metres to 1,500 metres over a horizontal distance of less than 150 kilometres. Along the escarpment is a range of mountains, in the west the Kunlun Mountains separate the plateau from the Tarim Basin. About halfway across the Tarim the bounding range becomes the Altyn-Tagh, in the V formed by this split is the western part of the Qaidam Basin. The Altyn-Tagh ends near the Dangjin pass on the Dunhuang-Golmud road, to the west are short ranges called the Danghe, Yema, Shule, and Tulai Nanshans. The easternmost range is the Qilian Mountains, the line of mountains continues east of the plateau as the Qin Mountains which separate the Ordos Region from Sichuan. North of the runs the Gansu or Hexi Corridor which was the main silk-road route from China proper to the West. The plateau is an arid steppe interspersed with mountain ranges. Annual precipitation ranges from 100 to 300 millimetres and falls mainly as hail, the southern and eastern edges of the steppe have grasslands which can sustainably support populations of nomadic herdsmen, although frost occurs for six months of the year. Permafrost occurs over parts of the plateau. Proceeding to the north and northwest, the plateau becomes progressively higher, colder and drier, here the average altitude exceeds 5,000 metres and winter temperatures can drop to −40 °C. The geological history of the Tibetan Plateau is closely related to that of the Himalayan mountain range, the Himalayas are among the youngest mountain ranges on the planet and consist mostly of uplifted sedimentary and metamorphic rock. Their formation is a result of a collision or orogeny along the convergent boundary between the Indo-Australian Plate and the Eurasian Plate. The collision began in the Upper Cretaceous period about 70 million years ago, since these sediments were light, they crumpled into mountain ranges rather than sinking to the floor
28.
Windward and leeward
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Windward is the direction upwind from the point of reference. Leeward is the direction downwind from the point of reference, the side of a ship that is towards the leeward is its lee side. If the vessel is heeling under the pressure of the wind, during the age of sail, the term weather was used as a synonym for windward in some contexts, as in the weather gage. Windward and leeward directions are important factors to consider when sailing a sailing ship, other terms with broadly the same meaning are widely used, particularly upwind and downwind. The windward vessel is normally the more maneuverable vessel, for this reason, rule 12 of the International Regulations for Preventing Collisions at Sea stipulates that the windward vessel gives way to the leeward vessel. The opposing warship to leeward could often do little but comply without exposing itself unduly and this was particularly important once artillery was introduced to naval warfare. The ships heeled away from the wind so that the vessel was exposing part of her bottom to shot. Leeward and windward refer respectively to what a game stalker would call downwind and upwind, the terms are used by seamen in relation to their ships but also in reference to islands in an archipelago and to the different sides of a single island. In the latter case, the side is that side of an island subject to the prevailing wind. The leeward side is the side protected by the elevation of the island from the prevailing wind, thus, leeward or windward siting is an important weather and climate factor on oceanic islands. In the case of an archipelago, windward islands are upwind and leeward islands are the downwind ones
29.
Rocky Mountains
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The Rocky Mountains, commonly known as the Rockies, are a major mountain range in western North America. The Rocky Mountains stretch more than 3,000 miles from the northernmost part of British Columbia, in western Canada, to New Mexico, in the Southwestern United States. Within the North American Cordillera, the Rockies are somewhat distinct from the Pacific Coast Ranges, the Rocky Mountains were initially formed from 80 million to 55 million years ago during the Laramide orogeny, in which a number of plates began to slide underneath the North American plate. The angle of subduction was shallow, resulting in a belt of mountains running down western North America. Since then, further tectonic activity and erosion by glaciers have sculpted the Rockies into dramatic peaks, at the end of the last ice age, humans started to inhabit the mountain range. The first mention of their present name by a European was in the journal of Jacques Legardeur de Saint-Pierre in 1752, the Rocky Mountains are commonly defined as stretching from the Liard River in British Columbia south to the Rio Grande in New Mexico. The United States definition of the Rockies includes the Cabinet and Salish Mountains of Idaho and their counterparts north of the Kootenai River, the Columbia Mountains, are considered a separate system in Canada, lying to the west of the huge Rocky Mountain Trench. This runs the length of British Columbia from its beginnings in the middle Flathead River valley in western Montana to the bank of the Liard River. The Rockies vary in width from 70 to 300 miles, also west of the Rocky Mountain Trench, farther north and facing the Muskwa Range across the trench, are the Stikine Ranges and Omineca Mountains of the Interior Mountains system of British Columbia. A small area east of Prince George, British Columbia on the side of the Trench. In Canada geographers define three main groups of ranges, the Continental Ranges, Hart Ranges and Muskwa Ranges, the Muskwa and Hart Ranges together comprise what is known as the Northern Rockies. The western edge of the Rockies includes ranges such as the Wasatch near Salt Lake City, the Great Basin and Columbia River Plateau separate these sub-ranges from distinct ranges further to the west, most prominent among which are the Sierra Nevada, Cascade Range and Coast Mountains. The Rocky Mountain System within the United States is a United States physiographic region, the Rocky Mountains are notable for containing the highest peaks in central North America. The ranges highest peak is Mount Elbert located in Colorado at 14,440 feet above sea level, Mount Robson in British Columbia, at 12,972 feet, is the highest peak in the Canadian Rockies. The Continental Divide of the Americas is located in the Rocky Mountains, triple Divide Peak in Glacier National Park is so named because water that falls on the mountain reaches not only the Atlantic and Pacific, but Hudson Bay as well. Farther north in Alberta, the Athabasca and other rivers feed the basin of the Mackenzie River, see Rivers of the Rocky Mountains for a list of rivers. Human population is not very dense in the Rocky Mountains, with an average of four people per square kilometer, however, the human population grew rapidly in the Rocky Mountain states between 1950 and 1990. The 40-year statewide increases in range from 35% in Montana to about 150% in Utah
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British Isles
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The British Isles are a group of islands off the north-western coast of continental Europe that consist of the islands of Great Britain, Ireland and over six thousand smaller isles. Situated in the North Atlantic, the islands have an area of approximately 315,159 km2. Two sovereign states are located on the islands, Ireland and the United Kingdom of Great Britain, the oldest rocks in the group are in the north west of Scotland, Ireland and North Wales and are 2,700 million years old. During the Silurian period the north-western regions collided with the south-east, the topography of the islands is modest in scale by global standards. Ben Nevis rises to an elevation of only 1,344 metres, and Lough Neagh, the climate is temperate marine, with mild winters and warm summers. The North Atlantic Drift brings significant moisture and raises temperatures 11 °C above the average for the latitude. This led to a landscape which was dominated by temperate rainforest. The region was re-inhabited after the last glacial period of Quaternary glaciation, Ireland, which became an island by 12,000 BC, was not inhabited until after 8000 BC. Great Britain became an island by 5600 BC, Hiberni, Pictish and Britons tribes, all speaking Insular Celtic, inhabited the islands at the beginning of the 1st millennium AD. Much of Brittonic-controlled Britain was conquered by the Roman Empire from AD43, the first Anglo-Saxons arrived as Roman power waned in the 5th century and eventually dominated the bulk of what is now England. Viking invasions began in the 9th century, followed by permanent settlements. Most of Ireland seceded from the United Kingdom after the Irish War of Independence, the term British Isles is controversial in Ireland, where there are objections to its usage due to the association of the word British with Ireland. The Government of Ireland does not recognise or use the term, as a result, Britain and Ireland is used as an alternative description, and Atlantic Archipelago has had limited use among a minority in academia, while British Isles is still commonly employed. Within them, they are sometimes referred to as these islands. The earliest known references to the islands as a group appeared in the writings of sea-farers from the ancient Greek colony of Massalia. The original records have been lost, however, later writings, e. g. Avienuss Ora maritima, in the 1st century BC, Diodorus Siculus has Prettanikē nēsos, the British Island, and Prettanoi, the Britons. Strabo used Βρεττανική, and Marcian of Heraclea, in his Periplus maris exteri, historians today, though not in absolute agreement, largely agree that these Greek and Latin names were probably drawn from native Celtic-language names for the archipelago. Along these lines, the inhabitants of the islands were called the Πρεττανοί, the shift from the P of Pretannia to the B of Britannia by the Romans occurred during the time of Julius Caesar
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Cyclone
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In meteorology, a cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure. A cyclone differs from a hurricane or typhoon only on the basis of location, a hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a cyclone occurs in the south Pacific or Indian Ocean. Cyclones are characterized by inward spiraling winds that rotate about a zone of low pressure, the largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes and dust devils lie within the smaller mesoscale, Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the Tropical Upper Tropospheric Trough during the summer months in the Northern Hemisphere. Cyclones have also seen on extraterrestrial planets, such as Mars. Cyclogenesis describes the process of formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones and these zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their cycle, extratropical cyclones occlude as cold air masses undercut the warmer air. A cyclones track is guided over the course of its 2 to 6 day life cycle by the flow of the subtropical jet stream. Weather fronts mark the boundary between two masses of air of different temperature, humidity, and densities, and are associated with the most prominent meteorological phenomena. Strong cold fronts typically feature narrow bands of thunderstorms and severe weather, such fronts form west of the circulation center and generally move from west to east, warm fronts form east of the cyclone center and are usually preceded by stratiform precipitation and fog. Warm fronts move poleward ahead of the cyclone path, occluded fronts form late in the cyclone life cycle near the center of the cyclone and often wrap around the storm center. Tropical cyclogenesis describes the process of development of tropical cyclones, Tropical cyclones form due to latent heat driven by significant thunderstorm activity, and are warm core. Cyclones can transition between extratropical, subtropical, and tropical phases, mesocyclones form as warm core cyclones over land, and can lead to tornado formation. Waterspouts can also form from mesocyclones, but more often develop from environments of high instability, henry Piddington published almost 40 papers dealing with tropical storms from Calcutta between 1835 and 1855 in The Journal of the Asiatic Society. He also coined the term cyclone, meaning the coil of a snake, in 1842, he published his landmark thesis, Laws of the Storms. There are a number of characteristics common to all cyclones
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High-pressure area
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A high-pressure area, high or anticyclone is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment. Winds within high-pressure areas flow outward from the higher areas near their centers towards the lower pressure areas further from their centers. Viewed from above this twist in wind direction is in the direction as the rotation of the planet. The strongest high-pressure areas are associated with air masses which push away out of polar regions during the winter when there is less sun to warm neighboring regions. These Highs change character and weaken once they move further over relatively warmer water bodies, many of the features of Highs may be understood in context of middle- or meso-scale and relatively enduring dynamics of a planets atmospheric circulation. For example, massive atmospheric subsidences occur as part of the branches of Ferrel cells. Hadley cells help form the ridge, steer tropical waves. The subtropical ridge also helps form most of the worlds deserts, on English-language weather maps, high-pressure centers are identified by the letter H. Weather maps in other languages may use different letters or symbols. The direction of flow around an atmospheric high-pressure area and a low-pressure area, as seen from above. High-pressure systems rotate clockwise in the northern Hemisphere, low-pressure systems rotate counterclockwise in the southern hemisphere, the scientific terms in English used to describe the weather systems generated by highs and lows were introduced in the mid-1800s, mostly by the British. The scientific theories which explain the general phenomena originated about two centuries earlier, the term Cyclone was coined by Henry Piddington of the British East India Company to describe the devastating storm of December 1789 in Coringa, India. A cyclone forms around a low-pressure area, anticyclone, the term for the kind of weather around a high-pressure area, was coined in 1877 by Francis Galton to indicate an area whose winds revolved in the opposite direction of a cyclone. In British English, the direction of clockwise is referred to as anticlockwise. So, both the earth and winds around a low-pressure area rotate counter-clockwise in the hemisphere. The opposite to two cases occurs in the case of a high. These results derive from the Coriolis effect, that explains in detail the physics. High-pressure systems form due to motion through the troposphere, the atmospheric layer where weather occurs. Preferred areas within a flow pattern in higher levels of the troposphere are beneath the western side of troughs
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Synoptic scale meteorology
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The synoptic scale in meteorology is a horizontal length scale of the order of 1000 kilometres or more. This corresponds to a horizontal scale typical of mid-latitude depressions, most high and low-pressure areas seen on weather maps such as surface weather analyses are synoptic-scale systems, driven by the location of Rossby waves in their respective hemisphere. Low-pressure areas and their related frontal zones occur on the edge of a trough within the Rossby wave pattern. Most precipitation areas occur near frontal zones, the word synoptic is derived from the Greek word συνοπτικός, meaning seen together. The Navier–Stokes equations applied to atmospheric motion can be simplified by scale analysis in the synoptic scale and it can be shown that the main terms in horizontal equations are Coriolis force and pressure gradient terms, therefore, one can use geostrophic approximation. In vertical coordinates, the equation simplifies to the hydrostatic equilibrium equation. The first weather maps in the 19th century were drawn well after the fact to help devise a theory on storm systems, use of surface analyses began first in the United States, spreading worldwide during the 1870s. Use of the Norwegian cyclone model for frontal analysis began in the late 1910s across Europe, surface weather analyses have special symbols which show frontal systems, cloud cover, precipitation, or other important information. For example, an H represents high pressure, implying good, an L represents low pressure, which frequently accompanies precipitation. Various symbols are used not just for frontal zones and other surface boundaries on weather maps, areas of precipitation help determine the frontal type and location. Mesoscale systems and boundaries such as cyclones, outflow boundaries. Isobars are commonly used to place surface boundaries from the horse latitudes poleward, the descriptor extratropical refers to the fact that this type of cyclone generally occurs outside of the tropics, in the middle latitudes of the planet. These are the phenomena which along with anti-cyclones, drive the weather over much of the Earth. An extratropical cyclone can transform into a storm, and from there into a tropical cyclone, if it dwells over warm waters and develops central convection. High-pressure systems are associated with light winds at the surface and subsidence through the lower portion of the troposphere. Subsidence will generally dry out an air mass by adiabatic, or compressional, thus, high pressure typically brings clear skies. During the day, since no clouds are present to reflect sunlight, there is more incoming solar radiation. At night, the absence of means that outgoing longwave radiation is not absorbed
34.
Mesocyclone
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A mesocyclone is a vortex of air within a convective storm. It is air that rises and rotates around a vertical axis and they are most often cyclonic, that is, associated with a localized low-pressure region within a severe thunderstorm. Such thunderstorms can feature strong surface winds and severe hail, mesocyclones often occur together with updrafts in supercells, within which tornadoes may form at the interchange with certain downdrafts. Mesocyclones are localized, approximately 2 km to 10 km in diameter within strong thunderstorms, thunderstorms containing persistent mesocyclones are supercell thunderstorms. Mesocyclones occur on the mesoscale, a general term used in meteorology to denote organization on scales from a few up to hundreds of kilometers. Doppler radar is used to identify mesocyclones, a mesovortex is a similar but typically smaller and weaker rotational feature associated with squall lines. Mesocyclones form when strong changes of wind speed and/or direction with height sets parts of the part of the atmosphere spinning in invisible tube-like rolls. The convective updraft of a thunderstorm then draw up this spinning air, tilting the rolls orientation upward, the wall cloud tends to form closer to the center of the mesocyclone. As it descends, a funnel cloud may form near its center and this is the first visible stage of tornadogenesis. The best way to detect and verify the presence of a mesocyclone is by Doppler weather radar, nearby high values of opposite sign within velocity data are how they are detected. Thus the word mesocyclone is associated with weather radar terminology, mesocyclones are most often identified in the right-rear flank of supercell thunderstorms and squall lines, and may be distinguished by a hook echo rotation signature on a weather radar map. Visual cues such as a wall cloud or tornado may also hint at the presence of a mesocyclone. This is why the term has entered into wider usage in connection with rotating features in severe storms, tornado formation generally occurs in one of two ways. In the first method, two conditions must be first satisfied, one, an invisible horizontal spinning effect must be first formed upon the Earths surface. This is usually formed by sudden changes in direction or speed. Second, a thundercloud, or occasionally a cumulus cloud, must be present, during a thunderstorm, the updrafts presented are occasionally powerful enough to lift the horizontal spinning row of air upwards, turning it into a vertical air column. This vertical air column then becomes the structure for the tornado. Tornadoes that form in this way are classified as weak tornadoes
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Polar low
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A polar low is a small-scale, short-lived atmospheric low pressure system that is found over the ocean areas poleward of the main polar front in both the Northern and Southern Hemispheres. The systems usually have a length scale of less than 1,000 kilometres. They are part of the class of mesoscale weather systems. Polar lows can be difficult to detect using conventional weather reports and are a hazard to high-latitude operations, such as shipping and gas, such winter storms can cause bitter cold and crop freezes. Polar lows have been referred to by other terms, such as polar mesoscale vortex, Arctic hurricane, Arctic low. Today the term is reserved for the more vigorous systems that have near-surface winds of at least 17 m/s. Polar lows were first identified on the satellite imagery that became available in the 1960s. Polar lows dissipate rapidly when they make landfall, Antarctic systems tend to be weaker than their northern counterparts since the air-sea temperature differences around the continent are generally smaller. However, vigorous polar lows can be found over the Southern Ocean, Polar lows can have a wide range of cloud signatures in satellite imagery, but two broad categories of cloud forms have been identified. The first is the spiraliform signature consisting of a number of cloud bands wrapped around the centre of the low and these systems are more common deep within the polar air. The second is a signature that is found more frequently with systems closer to the polar front. Polar lows form for a number of different reasons, and a spectrum of systems is observed on satellite imagery, a number of lows develop on horizontal temperature gradients through baroclinic instability, and these can have the appearance of small frontal depressions. At the other extreme are the polar lows with extensive cumulonimbus clouds, Polar lows can occur at any time during the year, but cyclogenesis takes on different characteristics depending on season. Although cyclonic activity is most prevalent in the Eurasian Arctic with approximately 15 cyclones per winter, polar lows also occur in Greenland, if you get the right atmospheric conditions during those two months, they can really accelerate the ice loss. If you don’t, they can slow down any melting momentum you had, in stark contrast, summer polar cyclones may not form for several years, and tend to be weaker than winter cyclones. The only infrastructure damage that occurs as a result of a polar cyclone is to oil. Some cargo and shipping vessels are also affected, although there are minimal or no reports of losses in recent years as the result of a polar low. Polar lows are very difficult to forecast and an approach is often used
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Mesoscale meteorology
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Mesoscale meteorology is the study of weather systems smaller than synoptic scale systems but larger than microscale and storm-scale cumulus systems. Horizontal dimensions generally range from around 5 kilometers to several hundred kilometers, examples of mesoscale weather systems are sea breezes, squall lines, and mesoscale convective complexes. As in synoptic frontal analysis, mesoscale analysis uses cold, warm, on weather maps mesoscale fronts are depicted as smaller and with twice as many bumps or spikes as the synoptic variety. Microscale meteorology Misoscale meteorology POLYGON experiment Storm scale Surface weather analysis Synoptic scale meteorology http, //meted. ucar. edu/mesoprim/mesodefn/print. htm
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Polar cyclone
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A polar vortex is an upper level low-pressure area lying near the Earths pole. There are two polar vortices in the Earths atmosphere, which overlie the North, and South Poles, each polar vortex is a persistent, large-scale, low pressure zone that rotates counter-clockwise at the North Pole, and clockwise at the South Pole. The bases of the two vortices are located in the middle and upper troposphere and extend into the stratosphere. Beneath that lies a large mass of cold, dense arctic air, the vortices weaken and strengthen from year to year. The interface between the dry air mass of the pole and the warm moist air mass further south defines the location of the polar front. The polar front is centered, roughly at 60° latitude, a polar vortex strengthens in the winter and weakens in the summer due to its dependence on the temperature difference between the equator and the poles. The vortices span less than 1,000 kilometers in diameter within which they rotate counter-clockwise in the Northern Hemisphere, as with other cyclones, their rotation is driven by the Coriolis effect. When the polar vortex is strong, there is a vortex with a jet stream that is well constrained near the polar front. When the northern vortex weakens, it separates into two or more vortices, the strongest of which are near Baffin Island, Canada and the other over northeast Siberia. The Antarctic vortex of the Southern Hemisphere is a low pressure zone that is found near the edge of the Ross ice shelf near 160 west longitude. When the polar vortex is strong, the mid-latitude Westerlies increase in strength and are persistent, when the polar vortex is weak, high pressure zones of the mid latitudes may push poleward, moving the polar vortex, jet stream, and polar front equatorward. The jet stream is seen to buckle and deviate south and this rapidly brings cold dry air into contact with the warm, moist air of the mid latitudes, resulting in a rapid and dramatic change of weather known as a cold snap. Ozone depletion occurs within the polar vortices – particularly over the Southern Hemisphere – reaching a maximum depletion in the spring, the polar vortex was first described as early as 1853. The phenomenons sudden stratospheric warming develops during the winter in the Northern Hemisphere and was discovered in 1952 with radiosonde observations at higher than 20 km. The phenomenon was mentioned frequently in the news and weather media in the cold North American winter of 2013-2014, Polar cyclones are low pressure zones embedded within the polar air masses, and exist year-round. The stratospheric polar vortex develops at latitudes above the jet stream. Horizontally, most polar vortices have a radius of less than 1,000 kilometres, since polar vortices exist from the stratosphere downward into the mid-troposphere, a variety of heights/pressure levels are used to mark its position. The 50 mb pressure surface is most often used to identify its stratospheric location, at the level of the tropopause, the extent of closed contours of potential temperature can be used to determine its strength
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Weather front
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A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena outside the tropics. In surface weather analyses, fronts are depicted using various colored triangles and half-circles, the air masses separated by a front usually differ in temperature and humidity. Cold fronts may feature narrow bands of thunderstorms and severe weather, Warm fronts are usually preceded by stratiform precipitation and fog. The weather usually clears quickly after a fronts passage, some fronts produce no precipitation and little cloudiness, although there is invariably a wind shift. Cold fronts and occluded fronts generally move from west to east, because of the greater density of air in their wake, cold fronts and cold occlusions move faster than warm fronts and warm occlusions. Mountains and warm bodies of water can slow the movement of fronts and this is most common over the open ocean. The Bergeron classification is the most widely accepted form of air mass classification, air mass classification involves three letters. The first letter describes its moisture properties, with c used for air masses. The second letter describes the characteristic of its source region, T for tropical, P for polar, A for arctic or Antarctic, M for monsoon, E for equatorial. The third letter is used to designate the stability of the atmosphere, if the air mass is colder than the ground below it, it is labeled k. If the air mass is warmer than the ground below it, it is labeled w. Fronts separate air masses of different types or origins, Surface weather analyses have special symbols which show frontal systems, cloud cover, precipitation, or other important information. For example, an H may represent high pressure, implying fair weather, an L on the other hand may represent low pressure, which frequently accompanies precipitation. Low pressure also creates surface winds deriving from high pressure zones, various symbols are used not just for frontal zones and other surface boundaries on weather maps, but also to depict the present weather at various locations on the weather map. In addition, areas of precipitation help determine the frontal type, there are two different meanings used within meteorology to describe weather around a frontal zone. The term anafront describes boundaries which show instability, meaning air rises rapidly along, a katafront is weaker, bringing smaller changes in temperature and moisture, as well as limited rainfall. Cold fronts often bring heavy thunderstorms, rain and hail, Cold front can produce sharper changes in weather and move up to twice as quickly as warm fronts, since cold air is denser than warm air and rapidly replaces the warm air preceding the boundary. Cold fronts come in association with a low-pressure area, the concept of colder, dense air wedging under the less dense warmer air is often used to depict how air is lifted along a frontal boundary. The cold air wedging underneath warmer air creates the strongest winds just above the ground surface and this lift would then form a narrow line of showers and thunderstorms if enough moisture were present
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Polar front
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In meteorology, the polar front is the boundary between the polar cell and the Ferrel cell in each hemisphere. At this boundary a sharp gradient in temperature occurs between two air masses, each at very different temperatures. The polar front arises as a result of polar air meeting warm tropical air. It is a front as the air masses are not moving against each other. Off the coast of eastern North America, especially in winter, the polar front theory says that mid-latitude cyclones form on boundaries between warm and cold air. In winter, the polar front shifts towards the Equator, whereas high pressure systems dominate more in the summer, graphic, Polar front - precipitation produced in zones of uplift Polar Front Theory of Midlatitude Cyclone Development
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Hadley cell
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This circulation creates the trade winds, tropical rain-belts and hurricanes, subtropical deserts and the jet streams. Each Hadley cell operates between zero and 30 to 40 degrees north and south and is responsible for the weather in the equatorial regions of the world. The major driving force of atmospheric circulation is solar heating, which is greatest near the equator, the atmospheric circulation transports energy polewards, thus reducing the resulting equator-to-pole temperature gradient. The mechanisms by which this is accomplished differs in tropical and extratropical latitudes, Hadley cells exist on either side of the equator. Each cell encircles the globe and acts to transport energy from the equator to 30th latitude, on the smaller synoptic scale, the energy transport is also accomplished by cyclones and anticyclones that cause relatively warm air to move polewards and cold air to move equatorwards. The large scale tropical overturning cell is referred to as the Hadley cell, why it extends only to 30 degrees latitude and what determines its strength are questions addressed by dynamical meteorology. Near the tropopause, as the air moves polewards in the Hadley cell, it is turned eastward by the Coriolis effect, analogously, near the surface, the equatorward return flow is turned to the west by the Coriolis effect. These resulting surface winds, with both an equatorward and a component, are referred to as the trade winds. The Hadley system provides an example of a thermally direct circulation, the thermodynamic efficiency of the Hadley system, considered as a heat engine, has been relatively constant over the 1979~2010 period, averaging 2. 6%. In the early 18th century, George Hadley, an English lawyer, what was no doubt correct in Halleys theory was that solar heating creates upward motion of equatorial air, and air mass from neighboring latitudes must flow in to replace the risen air mass. But for the component of the trade winds Halley had proposed that in moving across the sky the Sun heats the air mass differently over the course of the day. Hadley was not satisfied with that part of Halleys theory and rightly so, Hadley was the first to recognize that Earths rotation plays a role in the direction taken by an air mass as it moves relative to the Earth. Hadleys theory, published in 1735, remained unknown, but it was rediscovered several times. Among the re-discoverers was John Dalton, who learned of Hadleys priority. Over time the proposed by Hadley became accepted, and over time his name was increasingly attached to it. By the end of the 19th century it was shown that Hadleys theory was deficient in several respects, one of the first who accounted for the dynamics correctly was William Ferrel. It took many decades for the theory to become accepted. Hadleys theory was the accepted theory long enough to make his name become universally attached to the circulation pattern in the tropical atmosphere
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Sea surface temperature
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Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, air masses in the Earths atmosphere are highly modified by sea surface temperatures within a short distance of the shore. Localized areas of snow can form in bands downwind of warm water bodies within an otherwise cold air mass. Warm sea surface temperatures are known to be a cause of tropical cyclogenesis over the Earths oceans, tropical cyclones can also cause a cool wake, due to turbulent mixing of the upper 30 metres of the ocean. SST changes diurnally, like the air above it, but to a lesser degree, there is less SST variation on breezy days than on calm days. Coastal SSTs can cause winds to generate upwelling, which can significantly cool or warm nearby landmasses. Onshore winds can cause a considerable warm-up even in areas where upwelling is fairly constant and its values are important within numerical weather prediction as the SST influences the atmosphere above, such as in the formation of sea breezes and sea fog. It is also used to calibrate measurements from weather satellites, there are a variety of techniques for measuring this parameter that can potentially yield different results because different things are actually being measured. Away from the sea surface, general temperature measurements are accompanied by a reference to the specific depth of measurement. Sea surface temperature measurements are confined to the top portion of the ocean, SST was one of the first oceanographic variables to be measured. Benjamin Franklin suspended a mercury thermometer from a ship travelling between the United States and Europe in his survey of the Gulf stream in the late eighteenth century. SST was later measured by dipping a thermometer into a bucket of water that was drawn from the sea surface. The first automated technique for determining SST was accomplished by measuring the temperature of water in the port of large ships. These observations have a bias of around 0.6 °C due to the heat of the engine room. This bias has led to changes in the perception of global warming since 2000, fixed weather buoys measure the water temperature at a depth of 3 metres. Measurements of SST have had inconsistencies over the last 130 years due to the way they were taken, in the nineteenth century, measurements were taken in a bucket off of a ship. However, there was a variation in temperature because of the differences in buckets. Samples were collected in either a wood or a canvas bucket
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Enthalpy of vaporization
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The enthalpy of vaporization is a function of the pressure at which that transformation takes place. The heat of vaporization is temperature-dependent, though a constant heat of vaporization can be assumed for small temperature ranges, the heat of vaporization diminishes with increasing temperature and it vanishes completely at a certain point called the critical temperature. Above the critical temperature, the liquid and vapor phases are indistinguishable, values are usually quoted in J/mol or kJ/mol, although kJ/kg or J/g, and older units like kcal/mol, cal/g and Btu/lb are sometimes still used, among others. The increase in the energy can be viewed as the energy required to overcome the intermolecular interactions in the liquid. Hence helium has a particularly low enthalpy of vaporization,0.0845 kJ/mol, as the van der Waals forces between helium atoms are particularly weak. This is particularly true of metals, which often form covalently bonded molecules in the gas phase, in these cases, the enthalpy of atomization must be used to obtain a true value of the bond energy. An alternative description is to view the enthalpy of condensation as the heat which must be released to the surroundings to compensate for the drop in entropy when a gas condenses to a liquid. These two definitions are equivalent, the point is the temperature at which the increased entropy of the gas phase overcomes the intermolecular forces. Estimation of the enthalpy of vaporization of electrolyte solutions can be carried out using equations based on the chemical thermodynamic models. The vaporization of metals is a key step in metal vapor synthesis, gmelin-Handbuch der anorganischen Chemie /08 a. NIST Chemistry WebBook Young, Francis W. Sears, Mark W. Zemansky, Hugh D
43.
Wind shear
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Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as vertical or horizontal wind shear. Vertical wind shear is a change in speed or direction with change in altitude. Horizontal wind shear is a change in speed with change in lateral position for a given altitude. Wind shear has a significant effect during take-off and landing of aircraft due to its effects on control of the aircraft and this phenomenon is a concern for architects. Sound movement through the atmosphere is affected by shear, which can bend the wave front, causing sounds to be heard where they normally would not. The thermal wind concept explains how differences in speed at different heights are dependent on horizontal temperature differences. Wind shear refers to the variation of wind over either horizontal or vertical distances, airplane pilots generally regard significant wind shear to be a horizontal change in airspeed of 30 knots for light aircraft, and near 45 knots for airliners at flight altitude. Vertical speed changes greater than 4.9 knots also qualify as significant wind shear for aircraft, Low level wind shear can affect aircraft airspeed during take off and landing in disastrous ways, and airliner pilots are trained to avoid all microburst wind shear. Wind shear is also a key factor in the creation of severe thunderstorms, the additional hazard of turbulence is often associated with wind shear. Weather situations where shear is observed include, Weather fronts, significant shear is observed when the temperature difference across the front is 5 °C or more, and the front moves at 30 knots or faster. Because fronts are three-dimensional phenomena, frontal shear can be observed at any altitude between surface and tropopause, and therefore be seen both horizontally and vertically, vertical wind shear above warm fronts is more of an aviation concern than near and behind cold fronts due to their greater duration. Associated with upper level jet streams is a known as clear air turbulence. The CAT is strongest on the anticyclonic shear side of the jet, when a nocturnal low-level jet forms overnight above the Earths surface ahead of a cold front, significant low level vertical wind shear can develop near the lower portion of the low level jet. This is also known as wind shear since it is not due to nearby thunderstorms. When winds blow over a mountain, vertical shear is observed on the lee side, if the flow is strong enough, turbulent eddies known as rotors associated with lee waves may form, which are dangerous to ascending and descending aircraft. When on a clear and calm night, an inversion is formed near the ground. The change in wind can be 90 degrees in direction and 40 kt in speed, even a nocturnal low level jet can sometimes be observed
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Waterspout
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A waterspout is an intense columnar vortex that occurs over a body of water. Some are connected to a cumulus cloud, some to a cumuliform cloud. In the common form, it is a tornado over water. While it is weaker than most of its land counterparts. Most waterspouts do not suck up water, they are small, although rare, waterspouts have been observed in connection with lake-effect snow precipitation bands. Waterspouts exist on a microscale, where their environment is less than two kilometers in width, the cloud from which they develop can be as innocuous as a moderate cumulus, or as great as a supercell. While some waterspouts are strong and tornadic in nature, most are much weaker, weak tornadoes, known as landspouts, have been shown to develop in a similar manner. More than one waterspout can occur in the vicinity at the same time. As many as nine simultaneous waterspouts have been reported on Lake Michigan, waterspouts that are not associated with a rotating updraft of a supercell thunderstorm are known as non-tornadic or fair-weather waterspouts, and are by far the most common type. Fair-weather waterspouts occur in waters and are associated with dark, flat-bottomed. Waterspouts of this type rapidly develop and dissipate, having life cycles shorter than 20 minutes and they usually rate no higher than EF0 on the Enhanced Fujita scale, generally exhibiting winds of less than 30 m/s. They are most frequently seen in tropical and sub-tropical climates, with upwards of 400 per year observed in the Florida Keys, fair-weather waterspouts are very similar in both appearance and mechanics to landspouts, and largely behave as such if they move ashore. A tornado which travels from land to a body of water would also be considered a tornadic waterspout, however, in some areas, such as the Adriatic, Aegean and Ionian seas, tornadic waterspouts can make up half of the total number. A winter waterspout, also known as a devil, an icespout, an ice devil. The term winter waterspout is used to differentiate between the warm season waterspout and this rare winter season event. Very little is known about this phenomenon and only six known pictures of this event exist to date, four of which were taken in Ontario, there are a couple of critical criteria for the formation of a winter waterspout. Very cold temperatures need to be present over a body of water enough to produce fog resembling steam above the waters surface. Like the more efficient lake-effect snow events, winds focusing down the axis of long lakes enhance wind convergence and they are not restricted to saltwater, many have been reported on lakes and rivers including the Great Lakes and the St. Lawrence River
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Desert
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A desert is a barren area of land where little precipitation occurs and consequently living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation, about one third of the land surface of the world is arid or semi-arid. This includes much of the regions where little precipitation occurs. Deserts can be classified by the amount of precipitation falls, by the temperature that prevails. Deserts are formed by weathering processes as large variations in temperature between day and night put strains on the rocks which consequently break in pieces, although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter and the resulting fragments and this picks up particles of sand and dust and wafts them aloft in sand or dust storms. Wind-blown sand grains striking any solid object in their path can abrade the surface, rocks are smoothed down, and the wind sorts sand into uniform deposits. The grains end up as level sheets of sand or are piled high in billowing sand dunes, other deserts are flat, stony plains where all the fine material has been blown away and the surface consists of a mosaic of smooth stones. These areas are known as desert pavements and little further erosion takes place, other desert features include rock outcrops, exposed bedrock and clays once deposited by flowing water. Temporary lakes may form and salt pans may be left when waters evaporate, there may be underground sources of water in the form of springs and seepages from aquifers. Where these are found, oases can occur, plants and animals living in the desert need special adaptations to survive in the harsh environment. Plants tend to be tough and wiry with small or no leaves, water-resistant cuticles, some annual plants germinate, bloom and die in the course of a few weeks after rainfall while other long-lived plants survive for years and have deep root systems able to tap underground moisture. Animals need to cool and find enough food and water to survive. Many are nocturnal and stay in the shade or underground during the heat of the day and they tend to be efficient at conserving water, extracting most of their needs from their food and concentrating their urine. Some animals remain in a state of dormancy for long periods and they then reproduce rapidly while conditions are favorable before returning to dormancy. People have struggled to live in deserts and the surrounding lands for millennia. Nomads have moved their flocks and herds to wherever grazing is available, the cultivation of semi-arid regions encourages erosion of soil and is one of the causes of increased desertification. Many trade routes have been forged across deserts, especially across the Sahara Desert, large numbers of slaves were also taken northwards across the Sahara
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Evaporative cooler
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An evaporative cooler is a device that cools air through the evaporation of water. Evaporative cooling differs from typical air conditioning systems, which use vapor-compression or absorption refrigeration cycles, Evaporative cooling works by exploiting waters large enthalpy of vaporization. The temperature of dry air can be dropped significantly through the transition of liquid water to water vapor. This can cool air using much less energy than refrigeration, in extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants. The cooling potential for evaporative cooling is dependent on the wet bulb depression, in arid climates, evaporative cooling can reduce energy consumption and total equipment for conditioning as an alternative to compressor-based cooling. In climates not considered arid, indirect evaporative cooling can still take advantage of the cooling process without increasing humidity. Passive evaporative cooling strategies offer the benefits of mechanical evaporative cooling systems without the complexity of equipment. An earlier form of air cooling, the windcatcher, was used in ancient Egypt and they caught the wind, passed it over subterranean water in a qanat and discharged the cooled air into the building. Nowadays Iranians have changed the windcatcher into a cooler and use it widely. A typical design, as shown in a 1945 patent, includes a reservoir, a pump to circulate water over the excelsior pads. This design and this material remain dominant in evaporative coolers in the American Southwest, in the United States, the use of the term swamp cooler may be due to the odor of algae produced by early units. Passive evaporative cooling techniques in buildings, such as cooling towers, have only been developed and studied in the last 30 years. In 1986, two researchers at the University of Arizona, Tucson, W. Cunningham and T. Thompson, constructed the first passive evaporative cooling tower in Tucson, AZ. This performance data from this facility became the foundation of today’s evaporative cooling tower design guidelines. Evaporative cooling is the addition of water vapor into air, which causes a lowering of the temperature of the air and this conversion of sensible heat to latent heat is known as an adiabatic process because it occurs at a constant enthalpy value. Evaporative cooling therefore causes a drop in the temperature of air proportional to the sensible heat drop, Evaporative cooling can be visualized using a psychrometric chart by finding the initial air condition and moving along a line of constant enthalpy toward a state of higher humidity. A simple example of natural evaporative cooling is perspiration, or sweat, secreted by the body, the amount of heat transfer depends on the evaporation rate, however for each kilogram of water vaporized 2,257 kJ of energy are transferred. The evaporation rate depends on the temperature and humidity of the air, vapor-compression refrigeration uses evaporative cooling, but the evaporated vapor is within a sealed system, and is then compressed ready to evaporate again, using energy to do so
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Precipitation
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In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation include drizzle, rain, sleet, snow, graupel, Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and precipitates. Thus, fog and mist are not precipitation but suspensions, because the vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated, Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers, moisture that is lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed into clouds and rain. This process is active when freezing rain is occurring. A stationary front is often present near the area of freezing rain, provided necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely stratus and cumulonimbus. Eventually, the droplets will grow large enough to form raindrops. Lake-effect snowfall can be locally heavy, thundersnow is possible within a cyclones comma head and within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation, on the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. The movement of the trough, or intertropical convergence zone. Precipitation is a component of the water cycle, and is responsible for depositing the fresh water on the planet. Approximately 505,000 cubic kilometres of water falls as precipitation each year,398,000 cubic kilometres of it over the oceans and 107,000 cubic kilometres over land. Given the Earths surface area, that means the globally averaged annual precipitation is 990 millimetres, Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Precipitation may occur on celestial bodies, e. g. when it gets cold, Mars has precipitation which most likely takes the form of frost. Precipitation is a component of the water cycle, and is responsible for depositing most of the fresh water on the planet. Approximately 505,000 km3 of water falls as precipitation each year,398,000 km3 of it over the oceans, given the Earths surface area, that means the globally averaged annual precipitation is 990 millimetres. Mechanisms of producing precipitation include convective, stratiform, and orographic rainfall, Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice
