1.
Satellite imagery
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Satellite imagery consists of images of Earth or other planets collected by satellites. Imaging satellites are operated by governments and businesses around the world, Satellite imaging companies sell images under licence. Images are licensed to governments and businesses such as Apple Maps, the first images from space were taken on sub-orbital flights. The U. S-launched V-2 flight on October 24,1946 took one image every 1.5 seconds. With an apogee of 65 miles, these photos were from five times higher than the previous record, the first satellite photographs of Earth were made on August 14,1959 by the U. S. The first satellite photographs of the Moon might have made on October 6,1959 by the Soviet satellite Luna 3. The Blue Marble photograph was taken from space in 1972, and has very popular in the media. Also in 1972 the United States started the Landsat program, the largest program for acquisition of imagery of Earth from space, Landsat Data Continuity Mission, the most recent Landsat satellite, was launched on 11 February 2013. In 1977, the first real time satellite imagery was acquired by the United Statess KH-11 satellite system, all satellite images produced by NASA are published by NASA Earth Observatory and are freely available to the public. Several other countries have satellite imaging programs, and a collaborative European effort launched the ERS, there are also private companies that provide commercial satellite imagery. Images can be in visible colours and in other spectra, there are also elevation maps, usually made by radar images. Interpretation and analysis of imagery is conducted using specialized remote sensing applications. There are four types of resolution when discussing satellite imagery in remote sensing, spatial, spectral, temporal, and radiometric. GSD is a term containing the optical and systemic noise sources and is useful for comparing how well one sensor can see an object on the ground within a single pixel. For example, the GSD of Landsat is ~30m, which means the smallest unit that maps to a single pixel within an image is ~30m x 30m, the latest commercial satellite has a GSD of 0.41 m. This compares to a 0.3 m resolution obtained by some early military film based Reconnaissance satellite such as Corona, the resolution of satellite images varies depending on the instrument used and the altitude of the satellites orbit. For example, the Landsat archive offers repeated imagery at 30 meter resolution for the planet, Landsat 7 has an average return period of 16 days. For many smaller areas, images with resolution as high as 41 cm can be available, Satellite imagery is sometimes supplemented with aerial photography, which has higher resolution, but is more expensive per square meter
2.
NASA
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President Dwight D. Eisenhower established NASA in 1958 with a distinctly civilian orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29,1958, disestablishing NASAs predecessor, the new agency became operational on October 1,1958. Since that time, most US space exploration efforts have led by NASA, including the Apollo Moon landing missions, the Skylab space station. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the agency is also responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches. NASA shares data with various national and international such as from the Greenhouse Gases Observing Satellite. Since 2011, NASA has been criticized for low cost efficiency, from 1946, the National Advisory Committee for Aeronautics had been experimenting with rocket planes such as the supersonic Bell X-1. In the early 1950s, there was challenge to launch a satellite for the International Geophysical Year. An effort for this was the American Project Vanguard, after the Soviet launch of the worlds first artificial satellite on October 4,1957, the attention of the United States turned toward its own fledgling space efforts. This led to an agreement that a new federal agency based on NACA was needed to conduct all non-military activity in space. The Advanced Research Projects Agency was created in February 1958 to develop technology for military application. On July 29,1958, Eisenhower signed the National Aeronautics and Space Act, a NASA seal was approved by President Eisenhower in 1959. Elements of the Army Ballistic Missile Agency and the United States Naval Research Laboratory were incorporated into NASA, earlier research efforts within the US Air Force and many of ARPAs early space programs were also transferred to NASA. In December 1958, NASA gained control of the Jet Propulsion Laboratory, NASA has conducted many manned and unmanned spaceflight programs throughout its history. Some missions include both manned and unmanned aspects, such as the Galileo probe, which was deployed by astronauts in Earth orbit before being sent unmanned to Jupiter, the experimental rocket-powered aircraft programs started by NACA were extended by NASA as support for manned spaceflight. This was followed by a space capsule program, and in turn by a two-man capsule program. This goal was met in 1969 by the Apollo program, however, reduction of the perceived threat and changing political priorities almost immediately caused the termination of most of these plans. NASA turned its attention to an Apollo-derived temporary space laboratory, to date, NASA has launched a total of 166 manned space missions on rockets, and thirteen X-15 rocket flights above the USAF definition of spaceflight altitude,260,000 feet. The X-15 was an NACA experimental rocket-powered hypersonic research aircraft, developed in conjunction with the US Air Force, the design featured a slender fuselage with fairings along the side containing fuel and early computerized control systems
3.
Moderate-resolution imaging spectroradiometer
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The instruments capture data in 36 spectral bands ranging in wavelength from 0.4 µm to 14.4 µm and at varying spatial resolutions. Together the instruments image the entire Earth every 1 to 2 days, MODIS has used the marine optical buoy for vicarious calibration. MODIS is succeeded by the VIIRS instrument on board the Suomi NPP satellite launched in 2011, the MODIS characterization support team is dedicated to the production of high-quality MODIS calibrated product which is a precursor to every geophysical science product. A detailed description of the MCST mission statement and other details can be found at MCST Web, with its low spatial resolution but high temporal resolution, MODIS data is useful to track changes in the landscape over time. The United States Forest Services Remote Sensing Applications Center analyzes MODIS imagery on a basis to provide information for the management. The following MODIS Level 3 datasets are available from NASA, as processed by the Collection 5 software, most of the data is available in the HDF-EOS format — a variant of Hierarchical Data Format prescribed for the data derived from Earth Observing System missions. Imaging spectroscopy NASA World Wind Official NASA site MODIS bands and spectral ranges MODIS Images of the Day MODIS Image of the Day – Google Gadget referring to MODIS image of the day
4.
Sky
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The sky is everything that lies above the surface of the Earth, including the atmosphere and outer space. In the field of astronomy, the sky is called the celestial sphere. This is viewed from Earths surface as a dome where the Sun, stars, planets. The celestial sphere is divided into regions called constellations. Usually, the sky is used informally as the point of view from the Earths surface, however. In some cases, such as in discussing the weather, the sky refers to only the lower, during daylight, the sky appears to be blue because air scatters blue sunlight more than it scatters red. At night, the sky appears to be a dark surface or region scattered with stars. During the day, the Sun can be seen in the sky obscured by clouds. In the night sky the Moon, planets and stars are visible in the sky, some of the natural phenomena seen in the sky are clouds, rainbows, and aurorae. Lightning and precipitation can also be seen in the sky during storms, birds, insects, aircraft, and kites are often considered to fly in the sky. Due to human activities, smog during the day and light pollution during the night are often seen above large cities. Except for light that directly from the sun, most of the light in the day sky is caused by scattering. The scattering due to molecule sized particles is greater in the forward and backward directions than it is in the lateral direction. Scattering is significant for light at all visible wavelengths but is stronger at the end of the visible spectrum, meaning that the scattered light is bluer than its source. The remaining sunlight, having lost some of its wavelength components. Scattering also occurs more strongly in clouds. Individual water droplets exposed to light will create a set of colored rings. If a cloud is thick enough, scattering from water droplets will wash out the set of colored rings
5.
Okta
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In meteorology, an okta is a unit of measurement used to describe the amount of cloud cover at any given location such as a weather station. Sky conditions are estimated in terms of how many eighths of the sky are covered in cloud, in addition, in the SYNOP code there is an extra cloud cover indicator 9 indicating that the sky is totally obscured, usually due to dense fog or heavy snow. Although relatively straightforward to measure, oktas only estimate cloud cover in terms of the area of the sky covered by clouds and they do not account for cloud type or thickness, and this limits their use for estimating cloud albedo or surface solar radiation receipt. Cloud oktas can also be measured using satellite imagery from geostationary satellites equipped with high-resolution image sensors such as Himawari-8, similar to traditional approaches, satellite images do not account for cloud composition
6.
Sunshine duration
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It is a general indicator of cloudiness of a location, and thus differs from insolation, which measures the total energy delivered by sunlight over a given period. Sunshine duration is usually expressed in hours per year, or in hours per day, the first measure indicates the general sunniness of a location compared with other places, while the latter allows for comparison of sunshine in various seasons in the same location. Another often-used measure is percentage ratio of recorded bright sunshine duration, an important use of sunshine duration data is to characterize the climate of sites, especially of health resorts. This also takes account the psychological effect of strong solar light on human well-being. It is often used to promote tourist destinations, if the Sun were to be above the horizon 50% of the time for a standard year consisting of 8,760 hours, apparent maximal daytime duration would be 4,380 hours for any point on Earth. However, there are physical and astronomical effects that change that picture, namely, atmospheric refraction allows the Sun to be still visible even when it physically sets below the horizon. For that reason, average daytime is longest in polar areas, places on the Arctic Circle have the longest total annual daytime,4,647 hours, while the North Pole receives 4,575. Because of elliptic nature of the Earths orbit, the Southern Hemisphere is not symmetrical, the Equator has a total daytime of 4,422 hours per year. Given the theoretical maximum of daytime duration for a given location, bright sunshine hours represent the total hours when the sunlight is stronger than a specified threshold, as opposed to just visible hours. Visible sunshine, for example, occurs around sunrise and sunset, measurement is performed by instruments called sunshine recorders. For the specific purpose of sunshine duration recording, Campbell–Stokes recorders are used, when the intensity exceeds a pre-determined threshold, the tape burns. The total length of the trace is proportional to the number of bright hours. Another type of recorder is the Jordan sunshine recorder, newer, electronic recorders have more stable sensitivity than that of the paper tape. In 2003, the duration was finally defined as the period during which direct solar irradiance exceeds a threshold value of 120 W/m². The sky is clear in these regions, and fair weather is virtually perpetual, the descending branch of the Hadley cell and the long-term lack of atmospheric disturbances helps to explain the seemingly endless supply of sunny, cloud-free days in the deserts. Low clouding conditions are associated with rainfall shortage, as seen in these dry regions. In the belt encompassing northern Chad and the Tibesti Mountains, northern Sudan, southern Libya, some places in the interior of the Arabian Peninsula receive 3, 600–3,800 hours of bright sunshine annually. The largest sun-baked region in the world is North Africa, the sunniest month in the world is December in Eastern Antarctica, with almost 23 hours of bright sun daily
7.
Cirrus cloud
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Cirrus is a genus of atmospheric cloud generally characterized by thin, wispy strands, giving the type its name from the Latin word cirrus, meaning a ringlet or curling lock of hair. This cloud can form anywhere between 16,500 and 45,000 feet in the sky, the strands of cloud sometimes appear in tufts of a distinctive form referred to by the common name of mares tails. On planet Earth, cirrus generally appears white or light gray in color and it forms when water vapor undergoes deposition at altitudes above 5,500 m in temperate regions and above 6,400 m in tropical regions. It also forms from the outflow of tropical cyclones or the anvils of cumulonimbus cloud, since cirrus clouds arrive in advance of the frontal system or tropical cyclone, it indicates that weather conditions may soon deteriorate. While it indicates the arrival of precipitation, cirrus clouds only produce fall streaks, jet stream-powered cirrus can grow long enough to stretch across continents while remaining only a few kilometers deep. When visible light interacts with the ice crystals in cirrus cloud, it produces optical phenomena such as sun dogs, Cirrus is known to raise the temperature of the air beneath the main cloud layer by an average of 10 °C. When the individual filaments become so extensive that they are virtually indistinguishable from one another, convection at high altitudes can produce another high-based genus called cirrocumulus, a pattern of small cloud tufts that contain droplets of supercooled water. Cirrus clouds form on planets, including Mars, Jupiter, Saturn, Uranus. They have even seen on Titan, one of Saturns moons. Some of these extraterrestrial cirrus clouds are composed of ammonia or methane ice rather than water ice, the term cirrus is also used for certain interstellar clouds composed of sub-micrometer-sized dust grains. Cirrus cloud ranges in thickness from 100 m to 8,000 m, with an average thickness of 1,500 m. There are, on average,30 ice crystals per liter, but this ranges from one ice crystal per 10,000 liters to 10,000 ice crystals per liter, a difference of eight orders of magnitude. The length of each of these ice crystals is usually 0.25 millimeters long, the ice crystals in contrails are much smaller than those in naturally occurring cirrus cloud, as they are around 0.001 millimeters to 0.1 millimeters in length. Cirrus can vary in temperature from −20 °C to −30 °C, the ice crystals in cirrus clouds have different shapes in addition to different sizes. Some shapes include solid columns, hollow columns, plates, rosettes, the shape of the ice crystals is determined by the air temperature, atmospheric pressure, and ice supersaturation. Cirrus in temperate regions typically have the shapes segregated by type, in the northern Arctic region, cirrus tend to be composed of only the columns, plates, and conglomerations, and these crystals tend to be at least four times larger than the minimum size. In Antarctica, cirrus are usually composed of only the columns, scientists have studied the characteristics of cirrus using several different methods. One, Light Detection and Ranging, gives highly accurate information on the altitude, length
8.
Climate
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Climate is the statistics of weather, usually over a 30-year interval. Climate differs from weather, in that weather only describes the conditions of these variables in a given region. A regions climate is generated by the system, which has five components, atmosphere, hydrosphere, cryosphere, lithosphere. The climate of a location is affected by its latitude, terrain, climates can be classified according to the average and the typical ranges of different variables, most commonly temperature and precipitation. The most commonly used classification scheme was the Köppen climate classification, the Bergeron and Spatial Synoptic Classification systems focus on the origin of air masses that define the climate of a region. Paleoclimatology is the study of ancient climates, Climate models are mathematical models of past, present and future climates. Climate change may occur long and short timescales from a variety of factors. For example, a 3°C change in mean annual temperature corresponds to a shift in isotherms of approximately 300–400 km in latitude or 500 m in elevation, therefore, species are expected to move upwards in elevation or towards the poles in latitude in response to shifting climate zones. Climate is commonly defined as the weather averaged over a long period, the standard averaging period is 30 years, but other periods may be used depending on the purpose. Climate also includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations, the classical period is 30 years, as defined by the World Meteorological Organization. These quantities are most often surface variables such as temperature, precipitation, Climate in a wider sense is the state, including a statistical description, of the climate system. The World Meteorological Organization describes climate normals as reference points used by climatologists to compare current climatological trends to that of the past or what is considered normal, a Normal is defined as the arithmetic average of a climate element over a 30-year period. A30 year period is used, as it is enough to filter out any interannual variation or anomalies. The WMO originated from the International Meteorological Organization which set up a commission for climatology in 1929. At its 1934 Wiesbaden meeting the commission designated the thirty-year period from 1901 to 1930 as the reference time frame for climatological standard normals. In 1982 the WMO agreed to update climate normals, and in these were completed on the basis of climate data from 1 January 1961 to 31 December 1990. The difference between climate and weather is usefully summarized by the popular phrase Climate is what you expect, weather is what you get. Over historical time spans there are a number of nearly constant variables that determine climate, including latitude, altitude, proportion of land to water and these change only over periods of millions of years due to processes such as plate tectonics
9.
Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions
10.
Spectrum
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A spectrum is a condition that is not limited to a specific set of values but can vary, without steps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism, as scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum. Spectrum has since been applied by analogy to topics outside of optics, thus, one might talk about the spectrum of political opinion, or the spectrum of activity of a drug, or the autism spectrum. In these uses, values within a spectrum may not be associated with precisely quantifiable numbers or definitions, such uses imply a broad range of conditions or behaviors grouped together and studied under a single title for ease of discussion. Nonscientific uses of the spectrum are sometimes misleading. For instance, a single left–right spectrum of opinion does not capture the full range of peoples political beliefs. Political scientists use a variety of biaxial and multiaxial systems to accurately characterize political opinion. In most modern usages of spectrum there is a theme between the extremes at either end. This was not always true in older usage, in Latin spectrum means image or apparition, including the meaning spectre. Spectral evidence is testimony about what was done by spectres of persons not present physically and it was used to convict a number of persons of witchcraft at Salem, Massachusetts in the late 17th century. The word spectrum was used to designate a ghostly optical afterimage by Goethe in his Theory of Colors and Schopenhauer in On Vision. The prefix spectro- is used to form words relating to spectra, for example, a spectrometer is a device used to record spectra and spectroscopy is the use of a spectrometer for chemical analysis. In the 17th century the word spectrum was introduced into optics by Isaac Newton, soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral density plot. The term spectrum was expanded to apply to other waves, such as sound waves that could also be measured as a function of frequency, frequency spectrum and power spectrum of a signal. The term now applies to any signal that can be measured or decomposed along a variable such as energy in electron spectroscopy or mass to charge ratio in mass spectrometry. Spectrum is also used to refer to a representation of the signal as a function of the dependent variable. Devices used to measure an electromagnetic spectrum are called spectrograph or spectrometer, the visible spectrum is the part of the electromagnetic spectrum that can be seen by the human eye. The wavelength of light ranges from 390 to 700 nm
11.
Climate change
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Climate change is a change in the statistical distribution of weather patterns when that change lasts for an extended period of time. Climate change may refer to a change in weather conditions. Climate change is caused by such as biotic processes, variations in solar radiation received by Earth, plate tectonics. Certain human activities have also identified as significant causes of recent climate change. Scientists actively work to understand past and future climate by using observations, more recent data are provided by the instrumental record. The most general definition of change is a change in the statistical properties of the climate system when considered over long periods of time. Accordingly, fluctuations over periods shorter than a few decades, such as El Niño, the term climate change is often used to refer specifically to anthropogenic climate change. Anthropogenic climate change is caused by activity, as opposed to changes in climate that may have resulted as part of Earths natural processes. In this sense, especially in the context of environmental policy, within scientific journals, global warming refers to surface temperature increases while climate change includes global warming and everything else that increasing greenhouse gas levels affect. A related term is climatic change, in 1966, the World Meteorological Organization proposed the term climatic change to encompass all forms of climatic variability on time-scales longer than 10 years, regardless of cause. Change was a given and climatic was used as an adjective to describe this kind of change, when it was realized that human activities had a potential to drastically alter the climate, the term climate change replaced climatic change as the dominant term to reflect an anthropogenic cause. Climate change was incorporated in the title of the Intergovernmental Panel on Climate Change, Climate change, used as a noun, became an issue rather than the technical description of changing weather. On the broadest scale, the rate at which energy is received from the Sun and this energy is distributed around the globe by winds, ocean currents, and other mechanisms to affect the climates of different regions. Factors that can shape climate are called climate forcings or forcing mechanisms, there are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. Some parts of the system, such as the oceans and ice caps, respond more slowly in reaction to climate forcings. There are also key factors which when exceeded can produce rapid change. Forcing mechanisms can be internal or external. Internal forcing mechanisms are natural processes within the system itself
12.
Amazon rainforest
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The Amazon rainforest, also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest in the Amazon biome that covers most of the Amazon basin of South America. This basin encompasses 7,000,000 square kilometres, of which 5,500,000 square kilometres are covered by the rainforest and this region includes territory belonging to nine nations. States or departments in four nations contain Amazonas in their names, the name Amazon is said to arise from a war Francisco de Orellana fought with the Tapuyas and other tribes. The women of the tribe alongside the men, as was their custom. Orellana derived the name Amazonas from the Amazons of Greek mythology, the rainforest likely formed during the Eocene era. It appeared following a reduction of tropical temperatures when the Atlantic Ocean had widened sufficiently to provide a warm. Following the Cretaceous–Paleogene extinction event, the extinction of the dinosaurs, from 66–34 Mya, the rainforest extended as far south as 45°. Climate fluctuations during the last 34 million years have allowed savanna regions to expand into the tropics, during the Oligocene, for example, the rainforest spanned a relatively narrow band. It expanded again during the Middle Miocene, then retracted to a mostly inland formation at the last glacial maximum, however, the rainforest still managed to thrive during these glacial periods, allowing for the survival and evolution of a broad diversity of species. During the mid-Eocene, it is believed that the basin of the Amazon was split along the middle of the continent by the Purus Arch. Water on the eastern side flowed toward the Atlantic, while to the west water flowed toward the Pacific across the Amazonas Basin, as the Andes Mountains rose, however, a large basin was created that enclosed a lake, now known as the Solimões Basin. Within the last 5–10 million years, this accumulating water broke through the Purus Arch, there is evidence that there have been significant changes in Amazon rainforest vegetation over the last 21,000 years through the Last Glacial Maximum and subsequent deglaciation. There is debate, however, over how extensive this reduction was, more than 56% of the dust fertilizing the Amazon rainforest comes from the Bodélé depression in Northern Chad in the Sahara desert. The dust contains phosphorus, important for plant growth, the yearly Sahara dust replaces the equivalent amount of phosphorus washed away yearly in Amazon soil from rains and floods. Up to 50 million tonnes of Sahara dust per year are blown across the Atlantic Ocean, CALIPSO uses a laser range finder to scan the Earths atmosphere for the vertical distribution of dust and other aerosols. CALIPSO regularly tracks the Sahara-Amazon dust plume, CALIPSO has measured variations in the dust amounts transported— an 86 percent drop between the highest amount of dust transported in 2007 and the lowest in 2011. A possibility causing the variation is the Sahel, a strip of land on the southern border of the Sahara. When rain amounts in the Sahel are higher, the volume of dust is lower, the higher rainfall could make more vegetation grow in the Sahel, leaving less sand exposed to winds to blow away
13.
Sahara
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The Sahara is the largest hot desert and the third largest desert in the world after Antarctica and the Arctic. Its area of 9,200,000 square kilometres is comparable to the area of the United States. The desert comprises much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile Valley in Egypt and Sudan. It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south, it is bounded by the Sahel, a belt of tropical savanna around the Niger River valley. The Sahara can be divided into several regions including, the western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Aïr Mountains, the Ténéré desert, the name Sahara is derived from ṣaḥārā, the plural of the Arabic word for desert. The Sahara covers large parts of Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Sudan and it covers 9 million square kilometres, amounting to 31% of Africa. If all areas with an annual precipitation of less than 250 mm were included. It is one of three physiographic provinces of the African massive physiographic division. The Sahara is mainly rocky hamada, Ergs form only a minor part, wind or rare rainfall shape the desert features, sand dunes, dune fields, sand seas, stone plateaus, gravel plains, dry valleys, dry lakes, and salt flats. Unusual landforms include the Richat Structure in Mauritania, several deeply dissected mountains, many volcanic, rise from the desert, including the Aïr Mountains, Ahaggar Mountains, Saharan Atlas, Tibesti Mountains, Adrar des Iforas, and the Red Sea hills. The highest peak in the Sahara is Emi Koussi, a volcano in the Tibesti range of northern Chad. The central Sahara is hyperarid, with sparse vegetation, the northern and southern reaches of the desert, along with the highlands, have areas of sparse grassland and desert shrub, with trees and taller shrubs in wadis, where moisture collects. In the central, hyperarid region, there are subdivisions of the great desert, Tanezrouft, the Ténéré, the Libyan Desert, the Eastern Desert. These extremely arid areas often receive no rain for years, the northern limit also corresponds to the 100 mm isohyet of annual precipitation. To the south, the Sahara is bounded by the Sahel, the southern limit of the Sahara is indicated botanically by the southern limit of Cornulaca monacantha, or northern limit of Cenchrus biflorus, a grass typical of the Sahel. According to climatic criteria, the limit of the Sahara corresponds to the 150 mm isohyet of annual precipitation. The Sahara is the worlds largest low-latitude hot desert and this steady descending airflow causes a warming and a drying effect in the upper troposphere
14.
Nature
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Nature, in the broadest sense, is the natural, physical, or material world or universe. Nature can refer to the phenomena of the world. The study of nature is a part of science. Although humans are part of nature, human activity is understood as a separate category from other natural phenomena. The word nature is derived from the Latin word natura, or essential qualities, innate disposition, and in ancient times, literally meant birth. Natura is a Latin translation of the Greek word physis, which related to the intrinsic characteristics that plants, animals. This usage continued during the advent of scientific method in the last several centuries. Within the various uses of the word today, nature often refers to geology, for example, manufactured objects and human interaction generally are not considered part of nature, unless qualified as, for example, human nature or the whole of nature. Depending on the context, the term natural might also be distinguished from the unnatural or the supernatural. Earth is the planet known to support life, and its natural features are the subject of many fields of scientific research. Within the solar system, it is third closest to the sun, it is the largest terrestrial planet and its most prominent climatic features are its two large polar regions, two relatively narrow temperate zones, and a wide equatorial tropical to subtropical region. Precipitation varies widely with location, from several metres of water per year to less than a millimetre,71 percent of the Earths surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the land in the Northern Hemisphere. Earth has evolved through geological and biological processes that have left traces of the original conditions, the outer surface is divided into several gradually migrating tectonic plates. The interior remains active, with a layer of plastic mantle. This iron core is composed of a solid phase. Convective motion in the core generates electric currents through dynamo action, the atmospheric conditions have been significantly altered from the original conditions by the presence of life-forms, which create an ecological balance that stabilizes the surface conditions. Geology is the science and study of the solid and liquid matter that constitutes the Earth, the geology of an area evolves through time as rock units are deposited and inserted and deformational processes change their shapes and locations
15.
Weather
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Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the lowest level of the atmosphere, Weather refers to day-to-day temperature and precipitation activity, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time. When used without qualification, weather is understood to mean the weather of Earth. Weather is driven by air pressure, temperature and moisture differences between one place and another and these differences can occur due to the suns angle at any particular spot, which varies with latitude. The strong temperature contrast between polar and tropical air gives rise to the largest scale atmospheric circulations, the Hadley Cell, the Ferrel Cell, the Polar Cell, Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Because the Earths axis is tilted relative to its orbital plane, on Earths surface, temperatures usually range ±40 °C annually. Over thousands of years, changes in Earths orbit can affect the amount and distribution of energy received by the Earth, thus influencing long-term climate. Surface temperature differences in turn cause pressure differences, higher altitudes are cooler than lower altitudes as most atmospheric heating is due to contact with the Earths surface while radiative losses to space are mostly constant. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. The Earths weather system is a system, as a result. Human attempts to control the weather have occurred throughout history, and there is evidence that human activities such as agriculture, studying how the weather works on other planets has been helpful in understanding how weather works on Earth. A famous landmark in the Solar System, Jupiters Great Red Spot, is a storm known to have existed for at least 300 years. However, weather is not limited to planetary bodies, a stars corona is constantly being lost to space, creating what is essentially a very thin atmosphere throughout the Solar System. The movement of mass ejected from the Sun is known as the solar wind, on Earth, the common weather phenomena include wind, cloud, rain, snow, fog and dust storms. Less common events include natural disasters such as tornadoes, hurricanes, typhoons, almost all familiar weather phenomena occur in the troposphere. Weather does occur in the stratosphere and can affect weather lower down in the troposphere, Weather occurs primarily due to air pressure, temperature and moisture differences between one place to another. These differences can occur due to the sun angle at any particular spot, in other words, the farther from the tropics one lies, the lower the sun angle is, which causes those locations to be cooler due the spread of the sunlight over a greater surface. The strong temperature contrast between polar and tropical air gives rise to the large scale atmospheric circulation cells and the jet stream, Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow
16.
Season
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A season is a division of the year marked by changes in weather, ecology and hours of daylight. Seasons result from the orbit of the Earth around the Sun. During May, June, and July, the northern hemisphere is exposed to direct sunlight because the hemisphere faces the sun. The same is true of the hemisphere in November, December. It is the tilt of the Earth that causes the Sun to be higher in the sky during the months which increases the solar flux. However, due to lag, June, July, and August are the hottest months in the northern hemisphere and December, January. In temperate and subpolar regions, four calendar-based seasons are recognized, spring, summer, autumn or fall. Ecologists often use a model for temperate climate regions, prevernal, vernal, estival, serotinal, autumnal. Many tropical regions have two seasons, the rainy, wet, or monsoon season and the dry season, some have a third cool, mild, or harmattan season. Seasons often held special significance for agrarian societies, whose lives revolved around planting and harvest times, in some parts of the world, some other seasons capture the timing of important ecological events such as hurricane season, tornado season, and wildfire season. The most historically important of these are the three seasons—flood, growth, and low water—which were previously defined by the annual flooding of the Nile in Egypt. The seasons result from the Earths axis of rotation being tilted with respect to its orbital plane by an angle of approximately 23.5 degrees, regardless of the time of year, the northern and southern hemispheres always experience opposite seasons. This is because during summer or winter, one part of the planet is directly exposed to the rays of the Sun than the other. For approximately half of the year, the northern hemisphere tips toward the Sun, for the other half of the year, the same happens, but in the southern hemisphere instead of the northern, with the maximum around December 21. The two instants when the Sun is directly overhead at the Equator are the equinoxes. Also at that moment, both the North Pole and the South Pole of the Earth are just on the terminator, and hence day and night are equally divided between the northern and southern hemispheres. Around the March equinox, the northern hemisphere will be experiencing spring as the hours of daylight increase, the effect of axial tilt is observable as the change in day length and altitude of the Sun at noon during a year. Between this effect and the daylight hours, the axial tilt of the Earth accounts for most of the seasonal variation in climate in both hemispheres
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Winter
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Winter is the coldest season of the year in polar and temperate climates, between autumn and spring. Winter is caused by the axis of the Earth in that hemisphere being oriented away from the Sun, different cultures define different dates as the start of winter, and some use a definition based on weather. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, in many regions, winter is associated with snow and freezing temperatures. The moment of winter solstice is when the elevation with respect to the North or South Pole is at its most negative value, meaning this day will have the shortest day. The English word winter comes from the Proto-Indo-European root wend, relating to water, the tilt of the Earths axis relative to its orbital plane plays a large role in the formation of weather. The Earth is tilted at an angle of 23. 44° to the plane of its orbit, when it is winter in the Northern Hemisphere, the Southern Hemisphere faces the Sun more directly and thus experiences warmer temperatures than the Northern Hemisphere. Conversely, winter in the Southern Hemisphere occurs when the Northern Hemisphere is tilted more toward the Sun, from the perspective of an observer on the Earth, the winter Sun has a lower maximum altitude in the sky than the summer Sun. During winter in either hemisphere, the altitude of the Sun causes the sunlight to hit that hemisphere at an oblique angle. In regions experiencing winter, the amount of solar radiation is spread out over a larger area. This effect is compounded by the distance that the light must travel through the atmosphere. Compared with these effects, the changes in the distance of the earth from the sun are negligible, the manifestation of the meteorological winter in the northerly snow–prone parallels is highly variable depending on elevation, position versus marine winds and the amount of precipitation. A case in point is Canada, a country associated with tough winters. Winnipeg on the Great Plains at a distance from large bodies of water has a January high of −11.3 °C. In comparison, Vancouver on the coast with an influence from moderating Pacific winds has a January low of 1.4 °C with days well above freezing at 6.9 °C. Both areas are on the 49th parallel north and in the western half of the continent. Winter is often defined by meteorologists to be the three months with the lowest average temperatures. This corresponds to the months of December, January and February in the Northern Hemisphere, the coldest average temperatures of the season are typically experienced in January or February in the Northern Hemisphere and in June, July or August in the Southern Hemisphere. Blizzards often develop and cause many transportation delays, diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching −40 °F due to air with slightly higher moisture from aloft mixing with colder, surface based air
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Spring (season)
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Spring is one of the four conventional temperate seasons, following winter and preceding summer. There are various definitions of spring, but local usage of the term varies according to local climate, cultures. When it is spring in the Northern Hemisphere, it will be autumn in the Southern Hemisphere, at the spring equinox, days are approximately 12 hours long with day length increasing as the season progresses. Spring and springtime refer to the season, and also to ideas of rebirth, rejuvenation, renewal, resurrection, subtropical and tropical areas have climates better described in terms of other seasons, e. g. dry or wet, monsoonal or cyclonic. Often, cultures have locally defined names for seasons which have little equivalence to the terms originating in Europe, Spring is the time when many plants begin to grow and flower. Meteorologists generally define four seasons in many areas, spring, summer, autumn. These are demarcated by the values of their average temperatures on a monthly basis, the three warmest months are by definition summer, the three coldest months are winter and the intervening gaps are spring and autumn. Spring, when defined in this manner, can start on different dates in different regions, in most Northern Hemisphere, temperate locations, spring months are March, April and May, although differences exist from country to country. Most Southern Hemisphere, temperate locations have opposing seasons with spring in September, October and November, in Australia and New Zealand, spring conventionally begins on 1 September and ends 30 November. In some cultures in the Northern Hemisphere, the astronomical Vernal equinox is taken to mark the first day of spring, in Persian culture the first day of spring is the first day of the first month which begins on 20 or 21 March. In other traditions, the equinox is taken as mid-spring, similarly, according to the Celtic tradition, which is based solely on daylight and the strength of the noon sun, spring begins in early February and continues until early May. In Ireland, spring traditionally starts on February 1, St Brigids Day, the beginning of spring is not always determined by fixed calendar dates. These indicators, along with the beginning of spring, vary according to the local climate, most ecologists divide the year into six seasons that have no fixed dates. In addition to spring, ecological reckoning identifies an earlier separate prevernal season between the hibernal and vernal seasons and this is a time when only the hardiest flowers like the crocus are in bloom, sometimes while there is still some snowcover on the ground. During early spring, the axis of the Earth is increasing its tilt relative to the Sun, the hemisphere begins to warm significantly, causing new plant growth to spring forth, giving the season its name. Any snow begins to melt, swelling streams with runoff and any frosts become less severe, in climates that have no snow, and rare frosts, air and ground temperatures increase more rapidly. Many flowering plants bloom at this time of year, in a succession, sometimes beginning when snow is still on the ground. In normally snowless areas, spring may begin as early as February, heralded by the blooming of deciduous magnolias, cherries, and quince, or August in the same way
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Summer
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Summer is the hottest of the four temperate seasons, falling between spring and autumn. At the summer solstice, the days are longest and the nights are shortest, the date of the beginning of summer varies according to climate, tradition and culture. When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere, a variable seasonal lag means that the meteorological center of the season, which is based on average temperature patterns, occurs several weeks after the time of maximal insolation. Under meteorological definitions, all seasons are set to start at the beginning of a calendar month. This meteorological definition of summer also aligns with the commonly viewed notion of summer as the season with the longest days of the year, the meteorological reckoning of seasons is used in Australia, Austria, Denmark, the former Soviet Union and Japan. It is also used by many in the United Kingdom, in Ireland, the summer months according to the national meteorological service, Met Éireann, are June, July and August. However, according to the Irish Calendar, summer begins on 1 May, school textbooks in Ireland follow the cultural norm of summer commencing on 1 May rather than the meteorological definition of 1 June. Reckoning by hours of daylight alone, summer solstice marks the midpoint, not the beginning, midsummer takes place over the shortest night of the year, which is the summer solstice, or on a nearby date that varies with tradition. Where a seasonal lag of half a season or more is common, by this method, in North America, summer is the period from the summer solstice to the autumn equinox. The similar Canadian tradition starts summer on Victoria Day one week prior and ends, as in the United States, on Labour Day. In Chinese astronomy, summer starts on or around 5 May, with the known as lìxià, i. e. establishment of summer. In Australia and New Zealand, summer begins on 1 December. Summer is traditionally associated with hot or warm weather, in the Mediterranean regions, it is also associated with dry weather, while in other places it is associated with rainy weather. The wet season is the period of vegetation growth within the savanna climate regime. Where the wet season is associated with a shift in the prevailing winds. In the northern Atlantic Ocean, a tropical cyclone season occurs from 1 June to 30 November. The statistical peak of the Atlantic hurricane season is 10 September, the Northeast Pacific Ocean has a broader period of activity, but in a similar time frame to the Atlantic. The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and March, in the North Indian basin, storms are most common from April to December, with peaks in May and November
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Autumn
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Autumn, also known as fall in North American English, is one of the four temperate seasons. One of its features is the shedding of leaves from deciduous trees. Some cultures regard the autumnal equinox as mid-autumn, while others with a longer temperature lag treat it as the start of autumn. Meteorologists use a definition based on months, with autumn being September, October and November in the northern hemisphere, in North America, autumn is usually considered to start with the September equinox and end with the winter solstice. As daytime and nighttime temperatures decrease, trees shed their leaves, in traditional East Asian solar term, autumn starts on or around 8 August and ends on or about 7 November. In Ireland, the autumn months according to the meteorological service. In Australia and New Zealand, autumn officially begins on 1 March, the word autumn comes from the ancient Etruscan root autu- and has within it connotations of the passing of the year. It was borrowed by the neighbouring Romans, and became the Latin word autumnus, after the Roman era, the word continued to be used as the Old French word autompne or autumpne in Middle English, and was later normalized to the original Latin. In the Medieval period, there are examples of its use as early as the 12th century. Before the 16th century, harvest was the usually used to refer to the season. The alternative word fall for the season traces its origins to old Germanic languages, the exact derivation is unclear, with the Old English fiæll or feallan and the Old Norse fall all being possible candidates. However, these all have the meaning to fall from a height and are clearly derived either from a common root or from each other. The term came to denote the season in 16th century England, during the 17th century, English emigration to the British colonies in North America was at its peak, and the new settlers took the English language with them. While the term gradually became obsolete in Britain, it became the more common term in North America. The name backend, a common name for the season in Northern England, has today been largely replaced by the name autumn. Association with the transition from warm to cold weather, and its status as the season of the primary harvest, has dominated its themes. In Western cultures, personifications of autumn are usually pretty, well-fed females adorned with fruits, vegetables, many cultures feature autumnal harvest festivals, often the most important on their calendars. There are also the many North American Indian festivals tied to harvest of ripe foods gathered in the wild, the Chinese Mid-Autumn or Moon festival, and many others
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Tropics
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The tropics are a region of the Earth surrounding the equator. The tropics are also referred to as the zone and the torrid zone. The tropics include all the areas on the Earth where the Sun is at a point directly overhead at least once during the solar year. The tropics are distinguished from the climatic and biomatic regions of Earth, which are the middle latitudes. Tropical is sometimes used in a sense for a tropical climate to mean warm to hot and moist year-round. Many tropical areas have a dry and wet season, the wet season, rainy season or green season, is the time of year, ranging from one or more months, when most of the average annual rainfall in a region falls. Areas with wet seasons are disseminated across portions of the tropics and subtropics, under the Köppen climate classification, for tropical climates, a wet season month is defined as a month where average precipitation is 60 millimetres or more. Tropical rainforests technically do not have dry or wet seasons, since their rainfall is distributed through the year. When the wet season occurs during the season, or summer, precipitation falls mainly during the late afternoon. The wet season is a time when air quality improves, freshwater quality improves and vegetation grows significantly, floods cause rivers to overflow their banks, and some animals to retreat to higher ground. Soil nutrients diminish and erosion increases, the incidence of malaria increases in areas where the rainy season coincides with high temperatures. Animals have adaptation and survival strategies for the wetter regime, unfortunately, the previous dry season leads to food shortages into the wet season, as the crops have yet to mature. Regions within the tropics may well not have a tropical climate, there are alpine tundra and snow-capped peaks, including Mauna Kea, Mount Kilimanjaro, and the Andes as far south as the northernmost parts of Chile and Argentina. Under the Köppen climate classification, much of the area within the tropics is classed not as tropical but as dry including the Sahara Desert. Tropical plants and animals are those native to the tropics. Tropical ecosystems may consist of rainforests, dry forests, spiny forests, desert. There are often significant areas of biodiversity, and species present, particularly in rainforests. In biogeography, the tropics are divided into Paleotropics and Neotropics, together, they are sometimes referred to as the Pantropic
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Wet season
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The rainy season, or monsoon season, is the time of year when most of a regions average annual rainfall occurs. It usually lasts one or more months, the term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the tropics and subtropics, under the Köppen climate classification, for tropical climates, a wet season month is defined as a month where average precipitation is 60 millimetres or more. In contrast to areas with savanna climates and monsoon regimes, Mediterranean climates have wet winters, some areas with pronounced rainy seasons will see a break in rainfall mid-season, when the intertropical convergence zone or monsoon trough moves to higher latitudes in the middle of the warm season. When the wet season occurs during a season, or summer, precipitation falls mainly during the late afternoon. In the wet season, air quality improves, fresh water quality improves, rivers overflow their banks, and some animals retreat to higher ground. Soil nutrients diminish and erosion increases, the incidence of malaria increases in areas where the rainy season coincides with high temperatures, particularly in tropical areas. Some animals have adaptation and survival strategies for the wet season, often, the previous dry season leads to food shortages in the wet season, as the crops have yet to mature. In areas where the rainfall is associated with a wind shift. Further, much of the total each day occurs in the first minutes of the downpour. However, since rain forests have rainfall spread evenly through the year and it is different for places with a Mediterranean climate. This shift in the jet stream brings much of the precipitation to the region. The peninsula of Italy has weather very similar to the western United States in this regard, areas with a savanna climate in Sub-Saharan Africa, such as Ghana, Burkina Faso, Darfur, Eritrea, Ethiopia, and Botswana have a distinct rainy season. Also within the climate regime, Florida and South Texas have a rainy season. Northern Guyana has two wet seasons, one in spring and the other in early winter. In western Africa, there are two rainy seasons across southern sections, but only one across the north. Within the Mediterranean climate regime, the west coast of the United States and the Mediterranean coastline of Italy, Greece, similarly, the wet season in the Negev desert of Israel extends from October through May. At the boundary between the Mediterranean and monsoon climates lies the Sonoran desert, which receives the two rainy seasons associated with each climate regime, the wet season is known by many different local names throughout the world
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Storm
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A storm is any disturbed state of an environment or astronomical bodys atmosphere especially affecting its surface, and strongly implying severe weather. Heavy snowfall can allow special recreational activities to take place which would not be possible otherwise, the English word comes from Proto-Germanic *sturmaz meaning noise, tumult. Storms are created when a center of low pressure develops with a system of high pressure surrounding it and this combination of opposing forces can create winds and result in the formation of storm clouds, such as the cumulonimbus. Small localized areas of low pressure can form from hot air rising off hot ground, resulting in smaller disturbances such as dust devils, There are many varieties and names for storms, Ice storm — Ice storms are one of the most dangerous forms of winter storms. When surface temperatures are below freezing, but a layer of above-freezing air remains aloft, rain can fall into the freezing layer. In general,8 millimetres of accumulation is all that is required, especially in combination with breezy conditions, Ice storms also make unheated road surfaces too slick to drive upon. Ice storms can vary in range from hours to days and can cripple small towns. Blizzard — There are varying definitions for blizzards, both time and by location. In general, a blizzard is accompanied by winds, heavy snow. Snow storms, especially ones with a liquid equivalent and breezy conditions, can down tree limbs, cut off power. Ocean Storm — Storm conditions out at sea are defined as having sustained winds of 48 knots or greater, usually just referred to as a storm, these systems can sink vessels of all types and sizes. Firestorm — Firestorms are conflagrations which attain such intensity that they create and it is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires. The Peshtigo Fire is one example of a firestorm, Firestorms can also be deliberate effects of targeted explosives such as occurred as a result of the aerial bombings of Dresden. Nuclear detonations generate firestorms if high winds are not present, dust devil — a small, localized updraft of rising air. Wind storm— A storm marked by high wind with little or no precipitation, windstorm damage often opens the door for massive amounts of water and debris to cause further damage to a structure. European windstorms and derechos are two type of windstorms, high wind is also the cause of sandstorms in dry climates. Squall — sudden onset of wind increase of at least 16 knots or greater sustained for at least one minute, gale — An extratropical storm with sustained winds between 34-48 knots. Thunderstorm — A thunderstorm is a type of storm that generates lightning and it is normally accompanied by heavy precipitation
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Cumulonimbus cloud
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If observed during a storm, these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along cold front squall lines and these clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may develop as part of a supercell. Cumulonimbus is abbreviated Cb and are designated in the D2 family, towering cumulonimbus clouds are typically accompanied by smaller cumulus clouds. The cumulonimbus base may extend several miles across and occupy low to middle altitudes- formed at altitude from approximately 200 to 4,000 m, peaks typically reach to as much as 40,000 ft, with extreme instances as high as 70,000 ft or more. Well-developed cumulonimbus clouds are characterized by a flat, anvil-like top, the shelf of the anvil may precede the main clouds vertical component for many miles, and be accompanied by lightning. Occasionally, rising air parcels surpass the level and form an overshooting top culminating at the maximum parcel level. When vertically developed, this largest of all clouds usually extends through all three cloud regions, even the smallest cumulonimbus cloud dwarfs its neighbors in comparison. Cumulonimbus calvus, cloud with puffy top, similar to cumulus congestus which it develops from, cumulonimbus capillatus, cloud with cirrus-like, fibrous-edged top. Cumulonimbus incus, cloud with anvil top Arcus, low, horizontal cloud formation associated with the edge of thunderstorm outflow. Pannus, accompanied by a layer of fractus species cloud forming in precipitation. Pileus, small cap-like cloud over parent cumulonimbus, velum, a thin horizontal sheet that forms around the middle of a cumulonimbus. Incus, cumulonimbus with flat anvil-like cirriform top caused by wind shear where the air currents hit the inversion layer at the tropopause. Mamma or mammatus, consisting of bubble-like protrusions on the underside, tuba, column hanging from the cloud base which can develop into a funnel cloud or tornado. They are known to very low, sometimes just 20 feet above ground level. Flanking line is a line of small cumulonimbus or cumulus generally associated with severe thunderstorms, rain, precipitation that reaches the ground as liquid, often in a precipitation shaft. Virga, precipitation that evaporates before reaching the ground, cumulonimbus storm cells can produce torrential rain of a convective nature and flash flooding, as well as straight-line winds. Most storm cells die after about 20 minutes, when the precipitation causes more downdraft than updraft, causing the energy to dissipate
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Arcus cloud
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An arcus cloud is a low, horizontal cloud formation, usually appearing as an accessory cloud to a cumulonimbus. Roll clouds and shelf clouds are the two types of arcus. Roll clouds also may arise in the absence of thunderstorms, forming along the cold air currents of some sea breeze boundaries. A shelf cloud is a low, horizontal, wedge-shaped arcus cloud, a shelf cloud is attached to the base of the parent cloud, which is usually a thunderstorm, but could form on any type of convective clouds. Rising cloud motion often can be seen in the part of the shelf cloud, while the underside often appears turbulent. Cool, sinking air from a storm clouds downdraft spreads out across the land surface and this outflow cuts under warm air being drawn into the storms updraft. As the lower cooler air lifts the warm moist air, its water condenses, creating a cloud which often rolls with the different winds above, people seeing a shelf cloud may believe they have seen a wall cloud. This is likely a mistake, since an approaching shelf cloud appears to form a wall made of cloud, a shelf cloud usually appears on the leading edge of a storm, and a wall cloud will usually be at the rear of the storm. A sharp, strong gust front will cause the lowest part of the edge of a shelf cloud to be ragged and lined with rising fractus clouds. In a severe case there will be vortices along the edge, a very low shelf cloud accompanied by these signs is the best indicator that a potentially violent wind squall is approaching. An extreme example of this phenomenon looks almost like a tornado and is known as a gustnado, a roll cloud is a low, horizontal, tube-shaped, and relatively rare type of arcus cloud. They differ from shelf clouds by being completely detached from other cloud features, roll clouds usually appear to be rolling about a horizontal axis. They are a wave called a soliton, which is a wave that has a single crest. One of the most famous frequent occurrences is the Morning Glory cloud in Queensland, Australia, one of the main causes of the Morning Glory cloud is the mesoscale circulation associated with sea breezes that develop over the Cape York Peninsula and the Gulf of Carpentaria. However, similar features can be created by downdrafts from thunderstorms and are not exclusively associated with coastal regions. Coastal roll clouds have been seen in places, including California, the English Channel, Shetland Islands, the North Sea coast, coastal regions of Australia. Archived from the original on July 15,2013
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Downburst
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A downburst is a strong ground-level wind system that emanates from a point source above and blows radially, that is, in a straight line in all directions, from the point of contact at ground level. Downbursts are created by an area of significantly rain-cooled air that, after reaching ground level, dry downbursts are associated with thunderstorms with very little rain, while wet downbursts are created by thunderstorms with high amounts of rainfall. Microbursts and macrobursts are downbursts at very small and larger scales respectively, another variety, the heat burst, is created by vertical currents on the backside of old outflow boundaries and squall lines where rainfall is lacking. Heat bursts generate significantly higher temperatures due to the lack of rain-cooled air in their formation, Downbursts create vertical wind shear or microbursts, which is dangerous to aviation. This is because the properties of a downburst are completely different from those of a tornado. To differentiate between tornado damage and damage from a downburst, the term straight-line winds is applied to damage from microbursts, Downbursts are particularly strong downdrafts from thunderstorms. Downbursts in air that is free or contains virga are known as dry downbursts. Most downbursts are less than 4 km in extent, these are called microbursts, Downbursts larger than 4 km in extent are sometimes called macrobursts. Downbursts can occur over large areas, straight-line winds are very strong winds that can produce damage, demonstrating a lack of a rotational damage pattern. Such rotational damage patterns are associated with cyclonic storms including tornadoes, straight-line winds are common with the gust front of a thunderstorm or originate with a downburst from a thunderstorm. These events can cause damage, even in the absence of a tornado. The winds can reach 130 km/h and can last for periods of twenty minutes, such straight-line wind events are most common during the spring when instability is highest and weather fronts routinely cross the country. Straight-line wind events in the form of derechos can take place in areas outside of the traditional tornado alley, straight-line winds may be damaging to marine interests. Small ships, cutters and sailboats are at risk from this meteorological phenomenon, the formation of a downburst starts with hail or large raindrops falling through drier air. Hailstones melt and raindrops evaporate, pulling latent heat from surrounding air, cooler air has a higher density than the warmer air around it, so it sinks to the ground. As the cold air hits the ground it out and a mesoscale front can be observed as a gust front. Areas under and immediately adjacent to the downburst are the areas which receive the highest winds and rainfall, also, because the rain-cooled air is descending from the middle troposphere, a significant drop in temperatures is noticed. Due to interaction with the ground, the downburst quickly loses strength as it fans out, Downbursts usually last only a few minutes and then dissipate, except in the case of squall lines and derecho events
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Microburst
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A microburst is a small downdraft that moves in a way opposite to a tornado. Microbursts are found in strong thunderstorms, there are two types of microbursts within a thunderstorm, wet microbursts and dry microbursts. They go through three stages in their cycle, the downburst, outburst, and cushion stages, a microburst can be particularly dangerous to aircraft, especially during landing, due to the wind shear caused by its gust front. A microburst often has high winds that can knock over fully grown trees and they usually last from a couple of seconds to several minutes. Fujita also coined the term macroburst for downbursts larger than 4 km, a distinction can be made between a wet microburst which consists of precipitation and a dry microburst which typically consists of virga. Microbursts are recognized as capable of generating wind speeds higher than 75 m/s, Microbursts have also been called air bombs. When rain falls below the base or is mixed with dry air, it begins to evaporate. The cool air descends and accelerates as it approaches the ground, when the cool air approaches the ground, it spreads out in all directions and this divergence of the wind is the signature of the microburst. High winds spread out in type of pattern showing little or no curvature are known as straight-line winds. Wet microbursts are downbursts accompanied by significant precipitation at the surface which are warmer than their environment and these downbursts rely more on the drag of precipitation for downward acceleration of parcels than negative buoyancy which tend to drive dry microbursts. As a result, higher mixing ratios are necessary for these downbursts to form, melting of ice, particularly hail, appears to play an important role in downburst formation, especially in the lowest 1 km above ground level. These factors, among others, make forecasting wet microbursts a difficult task, the evolution of downbursts is broken down into three stages, the contact stage, the outburst stage, and the cushion stage. The virtual temperature correction usually is small and to a good approximation. In some storms this term has an effect on updrafts but there is not much reason to believe it has much of an impact on downdrafts. The second term is the effect of buoyancy on vertical motion, clearly, in the case of microbursts, one expects to find that B is negative meaning the parcel is cooler than its environment. This cooling typically takes place as a result of phase changes, precipitation particles that are small, but are in great quantity, promote a maximum contribution to cooling and, hence, to creation of negative buoyancy. The major contribution to this process is from evaporation, the last term is the effect of water loading. Whereas evaporation is promoted by large numbers of small droplets, it requires a few large drops to contribute substantially to the downward acceleration of air parcels
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Heat burst
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In meteorology, a heat burst is a rare atmospheric phenomenon characterized by gusty winds and a rapid increase in temperature and decrease in dew point. Heat bursts typically occur during night-time and are associated with decaying thunderstorms, the parcel descends rapidly, warming due to compression, overshoots its equilibrium level and reaches the surface, similar to a downburst. Recorded temperatures during heat bursts have reached well above 38 °C, more extreme events have also been documented, where temperatures have been reported to exceed 120 °F. However, such extreme events have never been officially verified. Heat bursts are characterized by extremely dry air and are sometimes associated with very strong, even damaging. In general, heat bursts occur during the spring and summer seasons. During the late spring and summer seasons, thunderstorms tend to generate day heating, due to a potential temperature increase, heat bursts normally occur at night. In rare cases, heat bursts have been recorded to occur during the daytime as well, Heat bursts have lasted for times spanning from a couple of minutes to several hours. The rare phenomenon is usually accompanied by gusty winds, extreme temperature changes. They occur near the end of a thunderstorm cluster. Dry air and a low-level inversion are also present during the storm, as the thunderstorm starts to dissipate, the layer of clouds start to rise. After the layer of clouds rise, a rain-cooled layer remains, the cluster shoots a burst of unsaturated air down towards the ground. In doing so, the system all of its up-draft related fuel. The raindrops begin to evaporate into dry air, which emphasizes the effects of the heat bursts, as the unsaturated air descends, the air pressure increases. The descending air parcel warms at the dry adiabatic rate of approximately 10° Celsius per 1000 meters of descent. The warm air from the cluster replaces the cool air on the ground, the effect is similar to someone blowing down on a puddle of water. On 4 March 1990, the National Weather Service in Goodland, Kansas detected a system that had weakening, light rain showers and it was followed by gusty winds and a temperature increase. A heat burst was being observed, the detection proved that heat bursts can occur in both summer months and winter months. The occurrence also proved that a thunderstorm was not needed in the development of heat bursts
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Dust storm
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A dust storm is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand, fine particles are transported by saltation and suspension, a process that moves soil from one place and deposits it in another. Drylands around North Africa and the Arabian peninsula are the main sources of airborne dust. Also with some contributions from Iran, Pakistan and India into the Arabian Sea, the term dust storm is more likely to be used when finer particles are blown long distances, especially when the dust storm affects urban areas. As the force of wind passing over loosely held particles increases, particles of sand first start to vibrate, as they repeatedly strike the ground, they loosen and break off smaller particles of dust which then begin to travel in suspension. At wind speeds above that which causes the smallest to suspend, there will be a population of dust grains moving by a range of mechanisms, suspension, saltation, a study from 2008 finds that the initial saltation of sand particles induces a static electric field by friction. Saltating sand acquires a negative charge relative to the ground which in turn loosens more sand particles which then begin saltating and this process has been found to double the number of particles predicted by previous theories. Particles become loosely held mainly due to drought or arid conditions, gust fronts may be produced by the outflow of rain-cooled air from an intense thunderstorm. S. Following the passage of a dry cold front, convective instability resulting from cooler air riding over heated ground can maintain the dust storm initiated at the front. In desert areas, dust and sand storms are most commonly caused by either thunderstorm outflows, the vertical extent of the dust or sand that is raised is largely determined by the stability of the atmosphere above the ground as well as by the weight of the particulates. In some cases, dust and sand may be confined to a shallow layer by a low-lying temperature inversion. In other instances, dust may be lifted as high as 20,000 feet high, drought and wind contribute to the emergence of dust storms, as do poor farming and grazing practices by exposing the dust and sand to the wind. One poor farming practice which contributes to dust storms is dryland farming, particularly poor dryland farming techniques are intensive tillage or not having established crops or cover crops when storms strike at particularly vulnerable times prior to revegetation. In a semi-arid climate, these practices increase susceptibility to dust storms, however, soil conservation practices may be implemented to control wind erosion. A sandstorm can transport and carry large volumes of sand unexpectedly, Dust storms can carry large amounts of dust, with the leading edge being composed of a wall of thick dust as much as 1.6 km high. Dust and sand storms which come off the Sahara Desert are locally known as a simoom or simoon, the haboob is a sandstorm prevalent in the region of Sudan around Khartoum, with occurrences being most common in the summer. The Sahara desert is a key source of dust storms, particularly the Bodélé Depression and an area covering the confluence of Mauritania, Mali, and Algeria. Saharan dust storms have increased approximately 10-fold during the half-century since the 1950s, causing loss in Niger, Chad, northern Nigeria
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Haboob
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A haboob is a type of intense dust storm carried on an atmospheric gravity current, also known as a weather front. Haboobs occur regularly in arid regions throughout the world, during thunderstorm formation, winds move in a direction opposite to the storms travel, and they move from all directions into the thunderstorm. When the storm collapses, and begins to release precipitation, wind directions reverse, gusting outward from the storm, Haboobs can also form when a strong thunderstorm weakens rapidly, and releases a microburst. When this downdraft of cold air, or downburst, reaches the ground, it blows dry, loose silt and clay up from the desert and this wall of dust can be up to 100 km wide and several kilometers in elevation. At their strongest, haboob winds often travel at 35–100 km/h, often rain does not appear at ground level as it evaporates in the hot, dry air. The evaporation cools the air even further and accelerates it. Occasionally, when the rain does persist, it can contain a quantity of dust. Severe cases are called mud storms, eye and respiratory system protection are advisable for anyone who must be outside during a haboob. Moving to shelter is highly advised during a strong event, Haboobs have been observed in the Sahara desert, as well as across the Arabian Peninsula, throughout Kuwait, and in the most arid regions of Iraq. Haboob winds in the Arabian Peninsula, Iraq, Kuwait are frequently created by the collapse of a thunderstorm, african haboobs result from the northward summer shift of the inter-tropical front into North Africa, bringing moisture from the Gulf of Guinea. Haboobs in Australia may be associated with cold fronts. As with haboobs in the Arabian Peninsula, Iraq and Kuwait, the arid and semiarid regions of North America—in fact, any dry region—may experience haboobs. In North America, the most common terms for these events are either dust storm or sandstorm. In the U. S. they frequently occur in the deserts of Arizona, including around the cities of Yuma and Phoenix, in New Mexico, including Albuquerque, in eastern California, and in Texas. They also sometimes accur in the Columbia Basin, of Eastern Washington, if the storms are strong enough, they can reach as far east as the Rathdrum Prairie and the Palouse, in the Idaho Panhandle Global dust storms on Mars have been compared to haboobs on Earth. Haboob Photos @ HikeArizona. COM Haboobs, Arizona Department of Transportation, the Bibliography of Aeolian Research Haboob on Winds of the World Short Video of the 5 July 2011 Arizona Haboob on YouTube Time-lapse video of the 5 July 2011 Arizona Haboob
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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
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Gale
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A gale is a very strong wind. There are conflicting definitions of how strong a wind must be to be considered a gale, the U. S. National Weather Service defines a gale as 34–47 knots of sustained surface winds. Forecasters typically issue gale warnings when winds of strength are expected. Other sources use minima as low as 28 knots and maxima as high as 90 knots, through 1986, the National Hurricane Center used the term gale to refer to winds of tropical force for coastal areas, between 33 knots and 63 knots. The 90 knots definition is very non-standard, a common alternative definition of the maximum is 55 knots. The most common way of measuring winds is with the Beaufort scale and it is an empirical measure for describing wind speed based mainly on observed sea conditions. Its full name is the Beaufort Wind Force Scale, on the Beaufort Wind Scale, a gale is classified as,7, Moderate Gale,8, Fresh Gale,9, Strong Gale and 10, Storm/Whole Gale. There is a unique Beaufort Scale number and a unique Arrow Indication for each type of Wind Description mentioned above, the word gale is derived from the older gail, but its origin is uncertain
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Sirocco
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It arises from a warm, dry, tropical airmass that is pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The Sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, the Siroccos duration may be as short as half a day or may last several days. Many people attribute health problems to the Sirocco, either because of the heat and dust along the African coastal regions, the dust within the Sirocco winds can cause abrasion in mechanical devices and penetrate buildings. Sirocco winds with speeds of up to 100 kilometres per hour are most common during autumn and they reach a peak in March and in November when it is very hot, with a maximum speed of about 100 km/h. When combined with a tide, the Sirocco can cause the Acqua Alta phenomenon in the Venetian Lagoon. Winds of the world Names of Winds Local Mediterranean winds Sirocco
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Firestorm
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A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires and wildfires, although the word has been used to describe certain large fires, the phenomenons determining characteristic is a fire with its own storm-force winds from every point of the compass. The Black Saturday bushfires and the Great Peshtigo Fire are possible examples of forest fires with some portion of combustion due to a firestorm. A firestorm is created as a result of the effect as the heat of the original fire draws in more and more of the surrounding air. This draft can be increased if a low-level jet stream exists over or near the fire. As the updraft mushrooms, strong inwardly-directed gusty winds develop around the fire and this would seem to prevent the firestorm from spreading on the wind, but the tremendous turbulence created may also cause the strong surface inflow winds to change direction erratically. A firestorm may also develop into a mesocyclone and induce true tornadoes/fire whirls and this occurred with the 2002 Durango fire, and probably with the much greater Peshtigo Fire. The greater draft of a firestorm draws in greater quantities of oxygen, the intense heat of a firestorm manifests largely as radiated heat, which may ignite flammable material at a distance ahead of the fire itself. This also serves to expand the area and the intensity of the firestorm, the very high temperatures ignite anything that might possibly burn, until the firestorm runs low on fuel. Thus the fire front is essentially stationary and the spread of fire is prevented by the in-rushing wind. At Hiroshima, this inrushing to feed the fire is said to have prevented the firestorm perimeter from expanding, large wildfire conflagrations are distinct from firestorms if they have moving fire fronts which are driven by the ambient wind and do not develop their own wind system like true firestorms. In Australia, the prevalence of eucalyptus trees that have oil in their leaves results in forest fires that are noted for their extremely tall, hence the bush fires appear more as a firestorm than a simple forest fire. Sometimes, emission of gases from swamps has a similar effect. For instance, methane explosions enforced the Peshtigo Fire, for example, the black rain that began to fall at ~20 minutes after the atomic bombing of Hiroshima produced in total 5–10 cm of black soot-filled rain in a 1–3 hour period. Moreover, if the conditions are right, a large pyrocumulus can grow into a pyrocumulonimbus and produce lightning, apart from city and forest fires, pyrocumulus clouds can also be produced by volcanic eruptions due to the comparable amounts of hot buoyant material formed. The same underlying combustion physics can also apply to structures such as cities during war or natural disaster. Firestorms are thought to have part of the mechanism of large urban fires, such as accompanied the 1906 San Francisco earthquake. Firestorms were also created by the raids of World War II in cities like Hamburg
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Lightning
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Lightning is a sudden electrostatic discharge that occurs during a thunder storm. This discharge occurs between electrically charged regions of a cloud, between two clouds, or between a cloud and the ground. The charged regions in the atmosphere temporarily equalize themselves through this discharge referred to as an if it hits an object on the ground. Lightning causes light in the form of plasma, and sound in the form of thunder, Lightning may be seen and not heard when it occurs at a distance too great for the sound to carry as far as the light from the strike or flash. This article incorporates public domain material from the National Oceanic and Atmospheric Administration document Understanding Lightning, the details of the charging process are still being studied by scientists, but there is general agreement on some of the basic concepts of thunderstorm electrification. The main charging area in a thunderstorm occurs in the part of the storm where air is moving upward rapidly and temperatures range from -15 to -25 Celsius. At that place, the combination of temperature and rapid upward air movement produces a mixture of super-cooled cloud droplets, small ice crystals, the updraft carries the super-cooled cloud droplets and very small ice crystals upward. At the same time, the graupel, which is larger and denser. The differences in the movement of the precipitation cause collisions to occur, when the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged. The updraft carries the positively charged ice crystals upward toward the top of the storm cloud, the larger and denser graupel is either suspended in the middle of the thunderstorm cloud or falls toward the lower part of the storm. The result is that the part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. This part of the cloud is called the anvil. While this is the charging process for the thunderstorm cloud. In addition, there is a small but important positive charge buildup near the bottom of the cloud due to the precipitation. Many factors affect the frequency, distribution, strength and physical properties of a lightning flash in a particular region of the world. These factors include ground elevation, latitude, prevailing wind currents, relative humidity, proximity to warm and cold bodies of water, to a certain degree, the ratio between IC, CC and CG lightning may also vary by season in middle latitudes. Lightnings relative unpredictability limits a complete explanation of how or why it occurs, the actual discharge is the final stage of a very complex process. At its peak, a thunderstorm produces three or more strikes to the Earth per minute
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Supercell
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A supercell is a thunderstorm that is characterized by the presence of a mesocyclone, a deep, persistently rotating updraft. For this reason, these storms are referred to as rotating thunderstorms. Of the four classifications of thunderstorms, supercells are the overall least common and have the potential to be the most severe, supercells are often isolated from other thunderstorms, and can dominate the local weather up to 32 kilometres away. Supercells are often put into three types, Classic, Low-precipitation, and High-precipitation. LP supercells are found in climates that are more arid, such as the high plains of the United States. Supercells are usually isolated from other thunderstorms, although they can sometimes be embedded in a squall line. Typically, supercells are found in the sector of a low pressure system propagating generally in a north easterly direction in line with the cold front of the low pressure system. Because they can last for hours, they are known as quasi-steady-state storms, supercells have the capability to deviate from the mean wind. If they track to the right or left of the wind, they are said to be right-movers or left-movers. Supercells can sometimes develop two separate updrafts with opposing rotations, which splits the storm into two supercells, one left-mover and one right-mover, supercells can be any size – large or small, low or high topped. They usually produce copious amounts of hail, torrential rainfall, strong winds, supercells are one of the few types of clouds that typically spawn tornadoes within the mesocyclone, although only 30% or fewer do so. Supercells can occur anywhere in the world under the weather conditions. The first storm to be identified as the type was the Wokingham storm over England. Browning did the work that was followed up by Lemon. Supercells occur occasionally in many other regions, including eastern China. The areas with highest frequencies of supercells are similar to those with the most occurrences of tornadoes, see tornado climatology and Tornado Alley. The current conceptual model of a supercell was described in Severe Thunderstorm Evolution and Mesocyclone Structure as Related to Tornadogenesis by Leslie R. Lemon, supercells derive their rotation through tilting of horizontal vorticity caused by wind shear. Strong updrafts lift the air turning about an axis and cause this air to turn about a vertical axis
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Thunderstorm
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Thunderstorms occur in association with a type of cloud known as a cumulonimbus. They are usually accompanied by winds, heavy rain, and sometimes snow, sleet, hail, or, in contrast. Thunderstorms may line up in a series or become a rainband, strong or severe thunderstorms, known as supercells, rotate as do cyclones. Thunderstorms result from the upward movement of warm, moist air. As the warm, moist air moves upward, it cools, condenses, as the rising air reaches its dew point temperature, water vapor condenses into water droplets or ice, reducing pressure locally within the thunderstorm cell. Any precipitation falls the long distance through the clouds towards the Earths surface, as the droplets fall, they collide with other droplets and become larger. Thunderstorms can form and develop in any location but most frequently within the mid-latitude. Thunderstorms are responsible for the development and formation of many weather phenomena. Thunderstorms, and the phenomena that occur along them, pose great hazards. Damage that results from thunderstorms is mainly inflicted by downburst winds, large hailstones, stronger thunderstorm cells are capable of producing tornadoes and waterspouts. There are four types of thunderstorms, single-cell, multi-cell cluster, multi-cell lines, supercell thunderstorms are the strongest and the most associated with severe weather phenomena. Mesoscale convective systems formed by vertical wind shear within the tropics and subtropics can be responsible for the development of hurricanes. Dry thunderstorms, with no precipitation, can cause the outbreak of wildfires from the heat generated from the lightning that accompanies them. Several means are used to study thunderstorms, weather radar, weather stations, past civilizations held various myths concerning thunderstorms and their development as late as the 18th century. Beyond the Earths atmosphere, thunderstorms have also observed on the planets of Jupiter, Saturn, Neptune. Warm air has a lower density than air, so warmer air rises upwards. Clouds form as relatively warmer air, carrying moisture, rises within cooler air, the moist air rises, and, as it does so, it cools and some of the water vapor in that rising air condenses. If enough instability is present in the atmosphere, this process will continue long enough for cumulonimbus clouds to form and produce lightning, Meteorological indices such as convective available potential energy and the lifted index can be used to assist in determining potential upward vertical development of clouds
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Storm surge
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Most casualties during tropical cyclones occur as the result of storm surges. The deadliest storm surge on record was the 1970 Bhola cyclone, the low-lying coast of the Bay of Bengal is particularly vulnerable to surges caused by tropical cyclones. The deadliest storm surge in the twenty-first century was caused by the Cyclone Nargis, the next deadliest in this century was caused by the Typhoon Haiyan, which killed more than 6,000 people in the central Philippines in 2013 and resulted in economic losses estimated at $14 billion. Louis, Diamondhead and Pass Christian in Mississippi, a high storm surge occurred in New York City from Hurricane Sandy in October 2012, with a high tide of 14 ft. The pressure effects of a tropical cyclone will cause the level in the open ocean to rise in regions of low atmospheric pressure. The rising water level will counteract the low pressure such that the total pressure at some plane beneath the water surface remains constant. This effect is estimated at a 10 mm increase in sea level for every millibar drop in atmospheric pressure, strong surface winds cause surface currents at a 45° angle to the wind direction, by an effect known as the Ekman Spiral. Wind stresses cause a phenomenon referred to as wind set-up, which is the tendency for water levels to increase at the downwind shore, intuitively, this is caused by the storm simply blowing the water towards one side of the basin in the direction of its winds. Because the Ekman Spiral effects spread vertically through the water, the effect is proportional to depth. The pressure effect and the wind set-up on an open coast will be driven into bays in the way as the astronomical tide. The Earths rotation causes the Coriolis effect, which bends currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. When this bend brings the currents into more contact with the shore it can amplify the surge. The effect of waves, while powered by the wind, is distinct from a storms wind-powered currents. Powerful wind whips up large, strong waves in the direction of its movement, although these surface waves are responsible for very little water transport in open water, they may be responsible for significant transport near the shore. When waves are breaking on a more or less parallel to the beach. The rainfall effect is experienced predominantly in estuaries, Hurricanes may dump as much as 12 in of rainfall in 24 hours over large areas, and higher rainfall densities in localized areas. As a result, watersheds can quickly surge water into the rivers that drain them and this can increase the water level near the head of tidal estuaries as storm-driven waters surging in from the ocean meet rainfall flowing from the estuary. This situation well exemplified by the southeast coast of Florida
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Tornado
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A tornado is a rapidly rotating column of air that spins while in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Most tornadoes have wind speeds less than 110 miles per hour, are about 250 feet across, the most extreme tornadoes can attain wind speeds of more than 300 miles per hour, are more than two miles in diameter, and stay on the ground for dozens of miles. Various types of tornadoes include the multiple vortex tornado, landspout and waterspout, waterspouts are characterized by a spiraling funnel-shaped wind current, connecting to a large cumulus or cumulonimbus cloud. They are generally classified as non-supercellular tornadoes that develop over bodies of water and these spiraling columns of air frequently develop in tropical areas close to the equator, and are less common at high latitudes. Other tornado-like phenomena that exist in nature include the gustnado, dust devil, fire whirls, downbursts are frequently confused with tornadoes, though their action is dissimilar. Tornadoes have been observed and documented on every continent except Antarctica, however, the vast majority of tornadoes occur in the Tornado Alley region of the United States, although they can occur nearly anywhere in North America. There are several scales for rating the strength of tornadoes, the Fujita scale rates tornadoes by damage caused and has been replaced in some countries by the updated Enhanced Fujita Scale. An F0 or EF0 tornado, the weakest category, damages trees, an F5 or EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes, Doppler radar data, photogrammetry, and ground swirl patterns may also be analyzed to determine intensity and assign a rating. The word tornado is a form of the Spanish word tronada. This in turn was taken from the Latin tonare, meaning to thunder and it most likely reached its present form through a combination of the Spanish tronada and tornar, however, this may be a folk etymology. A tornado is also referred to as a twister, and is also sometimes referred to by the old-fashioned colloquial term cyclone. The term cyclone is used as a synonym for tornado in the often-aired 1939 film The Wizard of Oz, the term twister is also used in that film, along with being the title of the 1996 tornado-related film Twister. A tornado is a rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud. For a vortex to be classified as a tornado, it must be in contact with both the ground and the cloud base. Scientists have not yet created a definition of the word, for example. Tornado refers to the vortex of wind, not the condensation cloud and this results in the formation of a visible funnel cloud or condensation funnel. There is some disagreement over the definition of cloud and condensation funnel
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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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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
42.
Anticyclone
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Effects of surface-based anticyclones include clearing skies as well as cooler, drier air. Fog can also form overnight within a region of higher pressure, sir Francis Galton first discovered anticyclones in the 1860s. Preferred areas within a flow pattern in higher levels of the hydrosphere are beneath the western side of troughs. High-pressure systems are referred to as anticyclones. Their circulation is sometimes referred to as cum sole, subtropical high pressure zones form along the descending portion of the Hadley cell circulation. Upper-level high-pressure areas lie over tropical cyclones due to their warm core nature, surface anticyclones form due to downward 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. Because they weaken with height, these systems are cold. Heating of the earth near the equator forces upward motion and convection along the trough or intertropical convergence zone. The divergence over the near-equatorial trough leads to air rising and moving away from the equator aloft, as air moves towards the mid-latitudes, it cools and sinks leading to subsidence near the 30° parallel of both hemispheres. This circulation known as the Hadley cell forms the subtropical ridge, many of the worlds deserts are caused by these climatological high-pressure areas. Because these anticyclones strengthen with height, they are known as warm core ridges, in the absence of rotation, the wind tends to blow from areas of high pressure to areas of low pressure. The stronger the pressure difference between a system and a low-pressure system, the stronger the wind. The coriolis force caused by Earths rotation gives winds within high-pressure systems their clockwise circulation in the northern hemisphere, friction with land slows down the wind flowing out of high-pressure systems and causes wind to flow more outward from the center. High-pressure systems are associated with light winds at the surface and subsidence of air from higher portions of the troposphere. Subsidence will generally warm an air mass by adiabatic heating, thus, high pressure typically brings clear skies. Because no clouds are present to reflect sunlight during the day, there is more incoming solar radiation, at night, the absence of clouds means that outgoing longwave radiation is not blocked, giving cooler diurnal low temperatures in all seasons. If the surface level relative humidity rises towards 100 percent overnight, the movement of continental arctic air masses to lower latitudes produces strong but vertically shallow high-pressure systems
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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
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Extratropical cyclone
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Extratropical cyclones are capable of producing anything from cloudiness and mild showers to heavy gales, thunderstorms, blizzards, and tornadoes. These types of cyclones are defined as large scale low pressure systems that occur in the middle latitudes of the Earth. In contrast with tropical cyclones, extratropical cyclones produce rapid changes in temperature and dew point along broad lines, called weather fronts, the term cyclone applies to numerous types of low pressure areas, one of which is the extratropical cyclone. The descriptor extratropical signifies that this type of cyclone generally occurs outside the tropics and they are termed mid-latitude cyclones if they form within those latitudes, or post-tropical cyclones if a tropical cyclone has intruded into the mid latitudes. Weather forecasters and the public often describe them simply as depressions or lows. Terms like frontal cyclone, frontal depression, frontal low, extratropical low, non-tropical low, Extratropical cyclones are classified mainly as baroclinic, because they form along zones of temperature and dewpoint gradient known as frontal zones. They can become barotropic late in their cycle, when the distribution of heat around the cyclone becomes fairly uniform with its radius. Extratropical cyclones form anywhere within the regions of the Earth. A study of extratropical cyclones in the Southern Hemisphere shows that between the 30th and 70th parallels, there are an average of 37 cyclones in existence during any 6-hour period, a separate study in the Northern Hemisphere suggests that approximately 234 significant extratropical cyclones form each winter. Extratropical cyclones form along linear bands of temperature/dewpoint gradient with significant vertical wind shear, initially, cyclogenesis, or low pressure formation, occurs along frontal zones near a favorable quadrant of a maximum in the upper level jetstream known as a jet streak. The favorable quadrants are usually at the rear and left front quadrants. The divergence causes air to rush out from the top of the air column and this in turn forces convergence in the low-level wind field and increased upward motion within the column. The increased upward motion causes atmospheric pressure at ground level to lower and this is because the upward air motion counteracts gravity, lessening the weight of the atmosphere in that location. The lowered pressure strengthens the cyclone, as the cyclone strengthens, the cold front sweeps towards the equator and moves around the back of the cyclone. Meanwhile, its associated warm front progresses more slowly, as the air ahead of the system is denser. Later, the cyclones occlude as the portion of the cold front overtakes a section of the warm front, forcing a tongue, or trowal. Eventually, the cyclone will become cold and begin to weaken. Atmospheric pressure can fall very rapidly when there are upper level forces on the system
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European windstorm
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European windstorm is a name given to the strongest extratropical cyclones which occur across the continent of Europe. They form as cyclonic windstorms associated with areas of low atmospheric pressure and they are most common in the autumn and winter months. On average, the month when most windstorms form is January, the seasonal average is 4.6 windstorms. However, when they track further south they can affect almost any country in Europe and these phenomena vary in terms of physical mechanisms, atmospheric structure, spatial extent, duration, severity level, predictability, and location relative to cyclone and fronts. On average these storms cause economic damage €1.9 billion per year and they rank as the second highest cause of global natural catastrophe insurance loss. Up to the half of the 19th century, European windstorms were named after the person who spotted them. Usually, they would be named either by the year, the date, however, a storm may still be named differently in different countries. 2011 storm Dagmar in Norway and Sweden is known as Patrick in Germany, an alternative Scottish naming system arose in 2011 via social media/Twitter which resulted in the humorous naming of Hurricane Bawbag and Hurricane Fannybaws. Such usage of the term Hurricane is not without precedent, as the 1968 Scotland storm was referred to as Hurricane Low Q, the UK Met Office and Irish forecasting service Met Éireann held discussions about developing a common naming system for Atlantic storms. An independent forecaster, the European Windstorm Centre, also has its own naming list, the university subsequently started to name every area of high or low pressure within its weather forecasts, from a list of 260 male and 260 female names submitted by its students. The female names were assigned to areas of low pressure while male names were assigned to areas of high pressure, the DWD subsequently banned the usage of the names by their offices during July 1991, after complaints had poured in about the naming system. However, the order was leaked to the German press agency, Deutsche Presse-Agentur, Germanys ZDF television channel subsequently ran a phone in poll on 17 July 1991 and claimed that 72% of the 40,000 responses favored keeping the names. This made the DWD pause and think about the naming system, during 1998 a debate started about if it was discrimination to name areas of high pressure with male names and the areas of low pressure with female names. The issue was resolved by alternating male and female names each year. The naming comes with the chance that the system will be notable. The money raised by this is used by the department to maintain weather observations at the Free University. Several European languages use cognates of the word huracán to indicate particularly strong winds occurring in Europe. The term hurricane as applied to these storms is not in reference to the structurally different tropical cyclone of the same name, in English, use of term hurricane to refer to European windstorms is mostly discouraged, as these storms do not display the structure of tropical storms
