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Meteorology
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Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not occur until the 18th century, the 19th century saw modest progress in the field after weather observation networks were formed across broad regions. Prior attempts at prediction of weather depended on historical data, Meteorological phenomena are observable weather events that are explained by the science of meteorology. Different spatial scales are used to describe and predict weather on local, regional, Meteorology, climatology, atmospheric physics, and atmospheric chemistry are sub-disciplines of the atmospheric sciences. Meteorology and hydrology compose the interdisciplinary field of hydrometeorology, the interactions between Earths atmosphere and its oceans are part of a coupled ocean-atmosphere system. Meteorology has application in diverse fields such as the military, energy production, transport, agriculture. The word meteorology is from Greek μετέωρος metéōros lofty, high and -λογία -logia -logy, varāhamihiras classical work Brihatsamhita, written about 500 AD, provides clear evidence that a deep knowledge of atmospheric processes existed even in those times. In 350 BC, Aristotle wrote Meteorology, Aristotle is considered the founder of meteorology. One of the most impressive achievements described in the Meteorology is the description of what is now known as the hydrologic cycle and they are all called swooping bolts because they swoop down upon the Earth. Lightning is sometimes smoky, and is then called smoldering lightning, sometimes it darts quickly along, at other times, it travels in crooked lines, and is called forked lightning. When it swoops down upon some object it is called swooping lightning, the Greek scientist Theophrastus compiled a book on weather forecasting, called the Book of Signs. The work of Theophrastus remained a dominant influence in the study of weather, in 25 AD, Pomponius Mela, a geographer for the Roman Empire, formalized the climatic zone system. According to Toufic Fahd, around the 9th century, Al-Dinawari wrote the Kitab al-Nabat, ptolemy wrote on the atmospheric refraction of light in the context of astronomical observations. St. Roger Bacon was the first to calculate the size of the rainbow. He stated that a rainbow summit can not appear higher than 42 degrees above the horizon, in the late 13th century and early 14th century, Kamāl al-Dīn al-Fārisī and Theodoric of Freiberg were the first to give the correct explanations for the primary rainbow phenomenon. Theoderic went further and also explained the secondary rainbow, in 1716, Edmund Halley suggested that aurorae are caused by magnetic effluvia moving along the Earths magnetic field lines. In 1441, King Sejongs son, Prince Munjong, invented the first standardized rain gauge and these were sent throughout the Joseon Dynasty of Korea as an official tool to assess land taxes based upon a farmers potential harvest. In 1450, Leone Battista Alberti developed a swinging-plate anemometer, and was known as the first anemometer, in 1607, Galileo Galilei constructed a thermoscope
2.
Turbulence
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Turbulence or turbulent flow is a flow regime in fluid dynamics characterized by chaotic changes in pressure and flow velocity. It is in contrast to a flow regime, which occurs when a fluid flows in parallel layers. Turbulence is caused by kinetic energy in parts of a fluid flow. For this reason turbulence is easier to create in low viscosity fluids, in general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other, consequently drag due to friction effects increases. This would increase the energy needed to pump fluid through a pipe, however this effect can also be exploited by such as aerodynamic spoilers on aircraft, which deliberately spoil the laminar flow to increase drag and reduce lift. The onset of turbulence can be predicted by a constant called the Reynolds number. However, turbulence has long resisted detailed physical analysis, and the interactions within turbulence creates a complex situation. Richard Feynman has described turbulence as the most important unsolved problem of classical physics, smoke rising from a cigarette is mostly turbulent flow. However, for the first few centimeters the flow is laminar, the smoke plume becomes turbulent as its Reynolds number increases, due to its flow velocity and characteristic length increasing. If the golf ball were smooth, the boundary layer flow over the front of the sphere would be laminar at typical conditions. However, the layer would separate early, as the pressure gradient switched from favorable to unfavorable. To prevent this happening, the surface is dimpled to perturb the boundary layer. This results in higher skin friction, but moves the point of boundary layer separation further along, resulting in form drag. The flow conditions in industrial equipment and machines. The external flow over all kind of such as cars, airplanes, ships. The motions of matter in stellar atmospheres, a jet exhausting from a nozzle into a quiescent fluid. As the flow emerges into this external fluid, shear layers originating at the lips of the nozzle are created and these layers separate the fast moving jet from the external fluid, and at a certain critical Reynolds number they become unstable and break down to turbulence. Biologically generated turbulence resulting from swimming animals affects ocean mixing, snow fences work by inducing turbulence in the wind, forcing it to drop much of its snow load near the fence
3.
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
4.
National Weather Service
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It is a part of the National Oceanic and Atmospheric Administration branch of the Department of Commerce, and is headquartered in Silver Spring, Maryland. The agency was known as the United States Weather Bureau from 1890 until it adopted its current name in 1970, the NWS performs its primary task through a collection of national and regional centers, and 122 local weather forecast offices. As the NWS is a government agency, most of its products are in the public domain, the agency was placed under the Secretary of War as Congress felt military discipline would probably secure the greatest promptness, regularity, and accuracy in the required observations. Within the Department of War, it was assigned to the U. S. Army Signal Service under Brigadier General Albert J. Myer, General Myer gave the National Weather Service its first name, The Division of Telegrams and Reports for the Benefit of Commerce. The agency first became an enterprise in 1890, when it became part of the Department of Agriculture. The first Weather Bureau radiosonde was launched in Massachusetts in 1937, the Bureau would later be moved to the Department of Commerce in 1940. On July 12,1950, bureau chief Francis W, the Weather Bureau became part of the Environmental Science Services Administration when that agency was formed in August 1966. The Environmental Science Services Administration was renamed the National Oceanic and Atmospheric Administration on October 1,1970, at this time, the Weather Bureau became the National Weather Service. NEXRAD, a system of Doppler radars deployed to improve the detection and warning time of local storms, replaced the WSR-57. Bob Glahn has written a history of the first hundred years of the National Weather Service. The NWS, through a variety of sub-organizations, issues different forecast products to users, although, throughout history, text forecasts have been the means of product dissemination, the NWS has been using more forecast products of a digital, gridded, image or other modern format. Each of the 122 Weather Forecast Offices send their graphical forecasts to a server to be compiled in the National Digital Forecast Database. The NDFD is a collection of weather observations used by organizations and the public, including precipitation amount, temperature. Specific points in the database can be accessed using an XML SOAP service. The National Weather Service issues many products relating to wildfires daily, for example, a Fire Weather Forecast, which have a forecast period covering up to seven days, is issued by local Weather Forecast Offices daily, with updates as needed. The forecasts contain weather information relevant to fire control and smoke management for the next 12 to 48 hours, such as direction and speed. The appropriate crews use this information to plan for staffing and equipment levels, the ability to conduct scheduled controlled burns, and assess the daily fire danger. Once per day, NWS meteorologists issue a coded fire weather forecast for specific United States Forest Service observation sites that are input into the National Fire Danger Rating System
5.
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
6.
Wind
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Wind is the flow of gases on a large scale. On the surface of the Earth, wind consists of the movement of air. Winds are commonly classified by their scale, their speed, the types of forces that cause them, the regions in which they occur. The strongest observed winds on a planet in the Solar System occur on Neptune, Winds have various aspects, an important one being its velocity, another the density of the gas involved, another its energy content or wind energy. In meteorology, winds are referred to according to their strength. Short bursts of high speed wind are termed gusts, strong winds of intermediate duration are termed squalls. Long-duration winds have various names associated with their strength, such as breeze, gale, storm. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet, within the tropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds, in areas that have variable terrain, mountain, Wind powers the voyages of sailing ships across Earths oceans. Hot air balloons use the wind to take trips, and powered flight uses it to increase lift. Areas of wind caused by various weather phenomena can lead to dangerous situations for aircraft. When winds become strong, trees and man-made structures are damaged or destroyed, Winds can shape landforms, via a variety of aeolian processes such as the formation of fertile soils, such as loess, and by erosion. Wind also affects the spread of wildfires, Winds can disperse seeds from various plants, enabling the survival and dispersal of those plant species, as well as flying insect populations. When combined with temperatures, wind has a negative impact on livestock. Wind affects animals food stores, as well as their hunting, Wind is caused by differences in the atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the pressure area. On a rotating planet, air will also be deflected by the Coriolis effect, globally, the two major driving factors of large-scale wind patterns are the differential heating between the equator and the poles and the rotation of the planet. Outside the tropics and aloft from frictional effects of the surface, near the Earths surface, friction causes the wind to be slower than it would be otherwise
7.
Wind shear
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Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as vertical or horizontal wind shear. Vertical wind shear is a change in speed or direction with change in altitude. Horizontal wind shear is a change in speed with change in lateral position for a given altitude. Wind shear has a significant effect during take-off and landing of aircraft due to its effects on control of the aircraft and this phenomenon is a concern for architects. Sound movement through the atmosphere is affected by shear, which can bend the wave front, causing sounds to be heard where they normally would not. The thermal wind concept explains how differences in speed at different heights are dependent on horizontal temperature differences. Wind shear refers to the variation of wind over either horizontal or vertical distances, airplane pilots generally regard significant wind shear to be a horizontal change in airspeed of 30 knots for light aircraft, and near 45 knots for airliners at flight altitude. Vertical speed changes greater than 4.9 knots also qualify as significant wind shear for aircraft, Low level wind shear can affect aircraft airspeed during take off and landing in disastrous ways, and airliner pilots are trained to avoid all microburst wind shear. Wind shear is also a key factor in the creation of severe thunderstorms, the additional hazard of turbulence is often associated with wind shear. Weather situations where shear is observed include, Weather fronts, significant shear is observed when the temperature difference across the front is 5 °C or more, and the front moves at 30 knots or faster. Because fronts are three-dimensional phenomena, frontal shear can be observed at any altitude between surface and tropopause, and therefore be seen both horizontally and vertically, vertical wind shear above warm fronts is more of an aviation concern than near and behind cold fronts due to their greater duration. Associated with upper level jet streams is a known as clear air turbulence. The CAT is strongest on the anticyclonic shear side of the jet, when a nocturnal low-level jet forms overnight above the Earths surface ahead of a cold front, significant low level vertical wind shear can develop near the lower portion of the low level jet. This is also known as wind shear since it is not due to nearby thunderstorms. When winds blow over a mountain, vertical shear is observed on the lee side, if the flow is strong enough, turbulent eddies known as rotors associated with lee waves may form, which are dangerous to ascending and descending aircraft. When on a clear and calm night, an inversion is formed near the ground. The change in wind can be 90 degrees in direction and 40 kt in speed, even a nocturnal low level jet can sometimes be observed
8.
Fog
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Fog consists of visible cloud water droplets or ice crystals suspended in the air at or near the Earths surface. Fog can be considered a type of low-lying cloud and is influenced by nearby bodies of water, topography. In turn, fog has affected many human activities, such as shipping, travel, the term fog is typically distinguished from the more generic term cloud in that fog is low-lying, and the moisture in the fog is often generated locally. By definition, fog reduces visibility to less than 1 kilometre, for aviation purposes in the UK, a visibility of less than 5 kilometres but greater than 999 metres is considered to be mist if the relative humidity is 70% or greater, below 70%, haze is reported. Fog forms when the difference between air temperature and dew point is less than 2.5 °C or 4 °F, Fog begins to form when water vapor condenses into tiny liquid water droplets suspended in the air. Water vapor normally begins to condense on condensation nuclei such as dust, ice, Fog, like its elevated cousin stratus, is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. Fog normally occurs at a relative humidity near 100% and this occurs from either added moisture in the air, or falling ambient air temperature. However, fog can form at lower humidities, and can fail to form with relative humidity at 100%. At 100% relative humidity, the air cannot hold additional moisture, thus, Fog can form suddenly and can dissipate just as rapidly. The sudden formation of fog is known as flash fog, Fog commonly produces precipitation in the form of drizzle or very light snow. Drizzle occurs when the humidity of fog attains 100% and the cloud droplets begin to coalesce into larger droplets. This can occur when the fog layer is lifted and cooled sufficiently, drizzle becomes freezing drizzle when the temperature at the surface drops below the freezing point. The inversion boundary varies its altitude primarily in response to the weight of the air above it, the marine layer, and any fogbank it may contain, will be squashed when the pressure is high, and conversely, may expand upwards when the pressure above it is lowering. Fog can form in a number of ways, depending on how the cooling that caused the condensation occurred, radiation fog is formed by the cooling of land after sunset by thermal radiation in calm conditions with clear sky. The warm ground produces condensation in the air by heat conduction. In perfect calm the fog layer can be less than a meter deep, radiation fogs occur at night, and usually do not last long after sunrise, but they can persist all day in the winter months especially in areas bounded by high ground. Radiation fog is most common in autumn and early winter, examples of this phenomenon include the Tule fog. Ground fog is fog that obscures less than 60% of the sky, advection fog occurs when moist air passes over a cool surface by advection and is cooled
9.
Water vapor
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Water vapor, water vapour or aqueous vapor, is the gaseous phase of water. It is one state of water within the hydrosphere, water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Unlike other forms of water, water vapor is invisible, under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is lighter than air and triggers convection currents that can lead to clouds, use of water vapor, as steam, has been important to humans for cooking and as a major component in energy production and transport systems since the industrial revolution. Likewise the detection of water vapor would indicate a similar distribution in other planetary systems. Water vapor is significant in that it can be evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects. Whenever a water molecule leaves a surface and diffuses into a surrounding gas, each individual water molecule which transitions between a more associated and a less associated state does so through the absorption or release of kinetic energy. The aggregate measurement of kinetic energy transfer is defined as thermal energy. Liquid water that becomes water vapor takes a parcel of heat with it, the amount of water vapor in the air determines how fast each molecule will return to the surface. When a net evaporation occurs, the body of water will undergo a net cooling directly related to the loss of water, in the US, the National Weather Service measures the actual rate of evaporation from a standardized pan open water surface outdoors, at various locations nationwide. Others do likewise around the world, the US data is collected and compiled into an annual evaporation map. The measurements range from under 30 to over 120 inches per year, formulas can be used for calculating the rate of evaporation from a water surface such as a swimming pool. In some countries, the evaporation rate far exceeds the precipitation rate, evaporative cooling is restricted by atmospheric conditions. Humidity is the amount of vapor in the air. The vapor content of air is measured with devices known as hygrometers, the measurements are usually expressed as specific humidity or percent relative humidity. This condition is referred to as complete saturation. Humidity ranges from 0 gram per cubic metre in dry air to 30 grams per cubic metre when the vapor is saturated at 30 °C, another form of evaporation is sublimation, by which water molecules become gaseous directly, leaving the surface of ice without first becoming liquid water. Sublimation accounts for the slow disappearance of ice and snow at temperatures too low to cause melting
10.
Thermodynamic temperature
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Thermodynamic temperature is the absolute measure of temperature and is one of the principal parameters of thermodynamics. Thermodynamic temperature is defined by the law of thermodynamics in which the theoretically lowest temperature is the null or zero point. At this point, absolute zero, the constituents of matter have minimal motion. In the quantum-mechanical description, matter at absolute zero is in its ground state, the International System of Units specifies a particular scale for thermodynamic temperature. It uses the Kelvin scale for measurement and selects the point of water at 273.16 K as the fundamental fixing point. Other scales have been in use historically, the Rankine scale, using the degree Fahrenheit as its unit interval, is still in use as part of the English Engineering Units in the United States in some engineering fields. ITS-90 gives a means of estimating the thermodynamic temperature to a very high degree of accuracy. Internal energy is called the heat energy or thermal energy in conditions when no work is done upon the substance by its surroundings. Internal energy may be stored in a number of ways within a substance, each way constituting a degree of freedom. At equilibrium, each degree of freedom will have on average the energy, k B T /2 where k B is the Boltzmann constant. Temperature is a measure of the random submicroscopic motions and vibrations of the constituents of matter. These motions comprise the internal energy of a substance, more specifically, the thermodynamic temperature of any bulk quantity of matter is the measure of the average kinetic energy per classical degree of freedom of its constituent particles. Translational motions are almost always in the classical regime, translational motions are ordinary, whole-body movements in three-dimensional space in which particles move about and exchange energy in collisions. Figure 1 below shows translational motion in gases, Figure 4 below shows translational motion in solids, Zero kinetic energy remains in a substance at absolute zero. Throughout the scientific world where measurements are made in SI units, many engineering fields in the U. S. however, measure thermodynamic temperature using the Rankine scale. By international agreement, the kelvin and its scale are defined by two points, absolute zero, and the triple point of Vienna Standard Mean Ocean Water. Absolute zero, the lowest possible temperature, is defined as being precisely 0 K, the triple point of water is defined as being precisely 273.16 K and 0.01 °C. This definition does three things, It fixes the magnitude of the unit as being precisely 1 part in 273.15 kelvins
11.
Radiosonde
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Modern radiosondes measure or calculate the following variables, altitude, pressure, temperature, relative humidity, wind, cosmic ray readings at high altitude and geographical position. Radiosondes measuring ozone concentration are known as ozonesondes, radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz. A radiosonde whose position is tracked as it ascends to give wind speed, most radiosondes have radar reflectors and are technically rawinsondes. A radiosonde that is dropped from an airplane and falls, rather than being carried by a balloon is called a dropsonde, radiosondes are an essential source of meteorological data, and hundreds are launched all over the world daily. This proved to be difficult because the kites were linked to the ground and were difficult to manoeuvre in gusty conditions. Furthermore, the sounding was limited to low altitudes because of the link to the ground, gustave Hermite and Georges Besançon, from France, were the first in 1892 to use a balloon to fly the meteograph. In 1898, Léon Teisserenc de Bort organized at the Observatoire de Météorologie Dynamique de Trappes the first regular use of these balloons. Data from these launches showed that the temperature lowered with height up to an altitude, which varied with the season. De Borts discovery of the tropopause and stratosphere was announced in 1902 at the French Academy of Sciences, other researchers, like Richard Aßmann and William Henry Dines, were working at the same times with similar instruments. In 1924, Colonel William Blaire in the U. S. Signal Corps did the first primitive experiments with weather measurements from balloon, the first true radiosonde that sent precise encoded telemetry from weather sensors was invented in France by Robert Bureau. Bureau coined the name radiosonde and flew the first instrument on January 7,1929, developed independently a year later, Pavel Molchanov flew a radiosonde on January 30,1930. Molchanovs design became a popular standard because of its simplicity and because it converted sensor readings to Morse code, working with a modified Molchanov sonde, Sergey Vernov was the first to use radiosondes to perform cosmic ray readings at high altitude. On April 1,1935, he took measurements up to 13.6 km using a pair of Geiger counters in a circuit to avoid counting secondary ray showers. The sondes were tracked for two days, a rubber or latex balloon filled with either helium or hydrogen lifts the device up through the atmosphere. The maximum altitude to which the balloon ascends is determined by the diameter, balloon sizes can range from 100 to 3,000 g. As the balloon ascends through the atmosphere, the pressure decreases, eventually, the balloon will expand to the extent that its skin will break, terminating the ascent. An 800 g balloon will burst at about 21 km, after bursting, a small parachute on the radiosondes support line carries it to Earth. A typical radiosonde flight lasts 60 to 90 minutes, one radiosonde from Clark Air Base, Philippines, reached an altitude of 155,092 ft
