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It became the basis of a modern international system that divides clouds into five physical forms which can be further divided or classified into altitude levels to derive ten basic genera. The main representative cloud types for each of these forms are stratiform, cumuliform, stratocumuliform, cumulonimbiform, and cir...
Low cloud
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Low-level clouds do not have any altitude-related prefixes. However mid-level stratiform and stratocumuliform types are given the prefix alto- while high-level variants of these same two forms carry the prefix cirro-. In both cases, strato- is dropped from the latter form to avoid double-prefixing.
Low cloud
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Genus types with sufficient vertical extent to occupy more than one level do not carry any altitude-related prefixes. They are classified formally as low- or mid-level depending on the altitude at which each initially forms, and are also more informally characterized as multi-level or vertical. Most of the ten genera d...
Low cloud
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Very low stratiform clouds that extend down to the Earth's surface are given the common names fog and mist, but have no Latin names. In the stratosphere and mesosphere, clouds have common names for their main types. They may have the appearance of stratiform veils or sheets, cirriform wisps, or stratocumuliform bands o...
Low cloud
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They are seen infrequently, mostly in the polar regions of Earth. Clouds have been observed in the atmospheres of other planets and moons in the Solar System and beyond. However, due to their different temperature characteristics, they are often composed of other substances such as methane, ammonia, and sulfuric acid, ...
Low cloud
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Tropospheric clouds can have a direct effect on climate change on Earth. They may reflect incoming rays from the sun which can contribute to a cooling effect where and when these clouds occur, or trap longer wave radiation that reflects back up from the Earth's surface which can cause a warming effect. The altitude, fo...
Low cloud
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In meteorology, a corona (plural coronae) is an optical phenomenon produced by the diffraction of sunlight or moonlight (or, occasionally, bright starlight or planetlight) by individual small water droplets and sometimes tiny ice crystals of a cloud or on a foggy glass surface. In its full form, a corona consists of se...
Corona (optical phenomenon)
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The angular diameter of a corona depends on the sizes of the water droplets involved; smaller droplets produce larger coronae. For the same reason, the corona is the most pronounced when the size of the droplets is most uniform. Coronae differ from halos in that the latter are formed by refraction (rather than diffract...
Corona (optical phenomenon)
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In meteorology, a cyclone () is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an anticyclone). Cyclones are characterized by inward-spiraling winds that rotate about...
Cyclone
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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.
Cyclone
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Cyclones have also been seen on extraterrestrial planets, such as Mars, Jupiter, and Neptune. Cyclogenesis is the process of cyclone formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones.
Cyclone
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These zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, extratropical cyclones occlude as cold air masses undercut the warmer air and become cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flo...
Cyclone
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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, and may on occasion be preceded by squall lines or dry...
Cyclone
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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.
Cyclone
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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.
Cyclone
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Waterspouts can also form from mesocyclones, but more often develop from environments of high instability and low vertical wind shear. In the Atlantic and the northeastern Pacific oceans, a tropical cyclone is generally referred to as a hurricane (from the name of the ancient Central American deity of wind, Huracan), i...
Cyclone
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In meteorology, a downburst is a strong downward and outward gushing wind system that emanates from a point source above and blows radially, that is, in straight lines in all directions from the area of impact at surface level. Capable of producing damaging winds, it may sometimes be confused with a tornado, where high...
Straight-line wind
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Downbursts are most often created by an area of significantly precipitation-cooled air that, after reaching the surface (subsiding), spreads out in all directions producing strong winds. Dry downbursts are associated with thunderstorms that exhibit very little rain, while wet downbursts are created by thunderstorms wit...
Straight-line wind
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A rare variety of dry downburst, 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 and compressional heating during descent. Do...
Straight-line wind
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Several fatal and historic crashes in past decades are attributed to the phenomenon and flight crew training goes to great lengths on how to properly recognize and recover from a downburst/wind shear event; wind shear recovery, among other adverse weather events, are standard topics across the world in flight simulator...
Straight-line wind
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In meteorology, a heat burst is a rare atmospheric phenomenon characterized by a sudden, localized increase in air temperature near the Earth's surface. Heat bursts typically occur during night-time and are associated with decaying thunderstorms. They are also characterized by extremely dry air and are sometimes associ...
Heat burst
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In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather (such as cloudy, windy, with possible rain or storms), while high-pressure areas are associated with lighter wind...
Low pressure system
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The formation process of a low-pressure area is known as cyclogenesis. In meteorology, atmospheric divergence aloft occurs in two kinds of places: The first is in the area on the east side of upper troughs, which form half of a Rossby wave within the Westerlies (a trough with large wavelength that extends through the t...
Low pressure system
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Thermal lows form due to localized heating caused by greater solar incidence over deserts and other land masses. Since localized areas of warm air are less dense than their surroundings, this warmer air rises, which lowers atmospheric pressure near that portion of the Earth's surface. Large-scale thermal lows over cont...
Low pressure system
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Low-pressure areas can also form due to organized thunderstorm activity over warm water. When this occurs over the tropics in concert with the Intertropical Convergence Zone, it is known as a monsoon trough. Monsoon troughs reach their northerly extent in August and their southerly extent in February.
Low pressure system
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When a convective low acquires a well-hot circulation in the tropics it is termed a tropical cyclone. Tropical cyclones can form during any month of the year globally but can occur in either the northern or southern hemisphere during December.
Low pressure system
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Atmospheric lift will also generally produce cloud cover through adiabatic cooling once the air temperature drops below the dew point as it rises, the cloudy skies typical of low-pressure areas act to dampen diurnal temperature extremes. Since clouds reflect sunlight, incoming shortwave solar radiation decreases, which...
Low pressure system
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The stronger the area of low pressure, the stronger the winds experienced in its vicinity. Globally, low-pressure systems are most frequently located over the Tibetan Plateau and in the lee of the Rocky mountains. In Europe (particularly in the British Isles and Netherlands), recurring low-pressure weather systems are ...
Low pressure system
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In meteorology, a precipitationshed is the upwind ocean and land surface that contributes evaporation to a given, downwind location's precipitation. The concept has been described as an "atmospheric watershed". The concept itself rests on a broad foundation of scholarly work examining the evaporative sources of rainfal...
Precipitationshed
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In meteorology, a pseudo-cold front is a boundary between a supercell's inflow region and the rear flank downdraft. It usually extends outward from a mesocyclone center, usually toward the south or southwest, and is characterized by advancing of the downdraft air toward the inflow region. It is a particular form of gus...
Pseudo-cold front
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In meteorology, absolute angular momentum is the angular momentum in an 'absolute' coordinate system (absolute time and space).
Absolute angular momentum
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In meteorology, air currents are concentrated areas of winds. They are mainly due to differences in atmospheric pressure or temperature. They are divided into horizontal and vertical currents; both are present at mesoscale while horizontal ones dominate at synoptic scale. Air currents are not only found in the troposph...
Air current
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In meteorology, an air mass is a volume of air defined by its temperature and humidity. Air masses cover many hundreds or thousands of square miles, and adapt to the characteristics of the surface below them. They are classified according to latitude and their continental or maritime source regions. Colder air masses a...
Air stream
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Continental and superior air masses are dry, while maritime and monsoon air masses are moist. Weather fronts separate air masses with different density (temperature or moisture) characteristics. Once an air mass moves away from its source region, underlying vegetation and water bodies can quickly modify its character. ...
Air stream
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In meteorology, an anemometer (from Ancient Greek άνεμος (ánemos) 'wind', and μέτρον (métron) 'measure') is a device that measures wind speed and direction. It is a common instrument used in weather stations. The earliest known description of an anemometer was by Italian architect and author Leon Battista Alberti (1404...
Hot-wire anemometry
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In meteorology, an inversion is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to an inversion of the air temperature lapse rate, in which case it is called a temperature inversion. Normally, air temperature decreases with an increase in altitude, but during an inve...
Atmospheric inversion
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An inversion can also suppress convection by acting as a "cap". If this cap is broken for any of several reasons, convection of any moisture present can then erupt into violent thunderstorms. Temperature inversion can notoriously result in freezing rain in cold climates.
Atmospheric inversion
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In meteorology, an occluded front is a type of weather front formed during cyclogenesis. The classical and usual view of an occluded front is that it starts when a cold front overtakes a warm front near a cyclone, such that the warm air is separated (occluded) from the cyclone center at the surface. The point where the...
Occluded front
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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, ranging from 0 oktas (completely clear sky) through to 8 oktas (completely overcast). In...
Okta
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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. Oktas are often referenced in aviation weather forecasts and low level forecast...
Okta
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In meteorology, an undular bore is a wave disturbance in the Earth's atmosphere and can be seen through unique cloud formations. They normally occur within an area of the atmosphere which is stable in the low levels after an outflow boundary or a cold front moves through. In hydraulics, an undular bore is a gentle bore...
Undular bore
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In meteorology, an updraft is a small-scale current of rising air, often within a cloud.
Vertical draft
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In meteorology, clear-air turbulence (CAT) is the turbulent movement of air masses in the absence of any visual clues, such as clouds, and is caused when bodies of air moving at widely different speeds meet. The atmospheric region most susceptible to CAT is the high troposphere at altitudes of around 7,000–12,000 metre...
Clear-air turbulence
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At lower altitudes it may also occur near mountain ranges. Thin cirrus clouds can also indicate high probability of CAT. CAT can be hazardous to the comfort, and occasionally the safety, of air travelers.
Clear-air turbulence
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In meteorology, clear-air turbulence (CAT) is the turbulent movement of air masses in the absence of any visual clues, such as clouds, and is caused when bodies of air moving at widely different speeds meet.In aviation, CAT is defined as "the detection by aircraft of high-altitude inflight bumps in patchy regions devoi...
Clear air turbulence
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In meteorology, cloud forcing, cloud radiative forcing (CRF) or cloud radiative effect (CRE) is the difference between the radiation budget components for average cloud conditions and cloud-free conditions. Much of the interest in cloud forcing relates to its role as a feedback process in the present period of global w...
Cloud forcing
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In meteorology, convective available potential energy (commonly abbreviated as CAPE), is the integrated amount of work that the upward (positive) buoyancy force would perform on a given mass of air (called an air parcel) if it rose vertically through the entire atmosphere. Positive CAPE will cause the air parcel to ris...
Available potential energy
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In meteorology, convective instability or stability of an air mass refers to its ability to resist vertical motion. A stable atmosphere makes vertical movement difficult, and small vertical disturbances dampen out and disappear. In an unstable atmosphere, vertical air movements (such as in orographic lifting, where an ...
Potential instability
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In meteorology, diurnal temperature variation is the variation between a high air temperature and a low temperature that occurs during the same day.
Diurnal temperature variation
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In meteorology, eyewall replacement cycles, also called concentric eyewall cycles, naturally occur in intense tropical cyclones, generally with winds greater than 185 km/h (115 mph), or major hurricanes (Category 3 or above). When tropical cyclones reach this intensity, and the eyewall contracts or is already small, so...
Eyewall replacement cycle
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government's hurricane modification experiment Project Stormfury. This project set out to seed clouds outside the eyewall, apparently causing a new eyewall to form and weakening the storm.
Eyewall replacement cycle
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When it was discovered that this was a natural process due to hurricane dynamics, the project was quickly abandoned.Almost every intense hurricane undergoes at least one of these cycles during its existence. Recent studies have shown that nearly half of all tropical cyclones, and nearly all cyclones with sustained wind...
Eyewall replacement cycle
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In meteorology, geopotential heights are used when creating forecasts and analyzing pressure systems. Geopotential heights represent the estimate of the real height of a pressure system above the average sea level. Geopotential heights for weather are divided up into several levels. The lowest geopotential height level...
Cold wake
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The moisture content, gained by using either the relative humidity or the precipitable water value, is used in creating forecasts for precipitation. The next level, 700 hPa (20.67 inHg), is at a height of 2,300–3,200 m (7,700–10,500 ft); 700 hPa is regarded as the highest point in the lower atmosphere. At this layer, b...
Cold wake
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The middle level of the atmosphere is at 500 hPa (14.76 inHg) or a height of 4,900–6,100 m (16,000–20,000 ft). The 500 hPa level is used for measuring atmospheric vorticity, commonly known as the spin of air. The relative humidity is also analyzed at this height in order to establish where precipitation is likely to ma...
Cold wake
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The next level occurs at 300 hPa (8.859 inHg) or a height of 8,200–9,800 m (27,000–32,000 ft). The top-most level is located at 200 hPa (5.906 inHg), which corresponds to a height of 11,000–12,000 m (35,000–41,000 ft). Both the 200 and 300 hPa levels are mainly used to locate the jet stream.
Cold wake
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In meteorology, haar or sea fret is a cold sea fog. It occurs most often on the east coast of Great Britain between April and September, when warm air passes over the cold North Sea. The term is also known as harr, hare, harl, har and hoar.
Haar (fog)
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In meteorology, helicity corresponds to the transfer of vorticity from the environment to an air parcel in convective motion. Here the definition of helicity is simplified to only use the horizontal component of wind and vorticity, and to only integrate in the vertical direction, replacing the volume integral with a on...
Helicity (fluid mechanics)
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This notion is used to predict the possibility of tornadic development in a thundercloud. In this case, the vertical integration will be limited below cloud tops (generally 3 km or 10,000 feet) and the horizontal wind will be calculated to wind relative to the storm in subtracting its motion: S R H = ∫ Z 1 Z 2 ( V → h ...
Helicity (fluid mechanics)
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That is why the Energy Helicity Index (EHI) has been created. It is the result of SRH multiplied by the CAPE (Convective Available Potential Energy) and then divided by a threshold CAPE: E H I = C A P E × S R H 160,000 {\displaystyle \mathrm {EHI} ={\frac {\mathrm {CAPE} \times \mathrm {SRH} }{\text{160,000}}}} This in...
Helicity (fluid mechanics)
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In meteorology, hodographs are used to plot winds from soundings of the Earth's atmosphere. It is a polar diagram where wind direction is indicated by the angle from the center axis and its strength by the distance from the center. In the figure to the right, at the bottom one finds values of wind at 4 heights above gr...
Hodograph
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One has to notice that direction are plotted as mentioned in the upper right corner. With the hodograph and thermodynamic diagrams like the tephigram, meteorologists can calculate: Wind shear: The lines uniting the extremities of successive vectors represent the variation in direction and value of the wind in a layer o...
Hodograph
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Turbulence: wind shear indicate the possible turbulence that would cause a hazard to aviation. Temperature advection: change of temperature in a layer of air can be calculated by the direction of the wind at that level and the direction of the wind shear with the next level. In the northern hemisphere, warm air is to t...
Hodograph
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In meteorology, hypotheses are often formulated using weather data up to the present and tested against future weather data, which ensures that, even subconsciously, future data could not influence the formulation of the hypothesis. Of course, such a discipline necessitates waiting for new data to come in, to show the ...
Data-snooping bias
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As another example, suppose that observers note that a particular town appears to have a cancer cluster, but lack a firm hypothesis of why this is so. However, they have access to a large amount of demographic data about the town and surrounding area, containing measurements for the area of hundreds or thousands of dif...
Data-snooping bias
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In meteorology, isopycnals are used to display different layers of gases in the atmosphere. In the atmosphere, varying degrees of humidity, temperature, and pressure change the density of air. Isopycnals are not used in meteorology as frequently as they are in oceanography, since the density gradients observed in the a...
Diapycnal mixing
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In meteorology, latent heat flux is the flux of energy from the Earth's surface to the atmosphere that is associated with evaporation or transpiration of water at the surface and subsequent condensation of water vapor in the troposphere. It is an important component of Earth's surface energy budget. Latent heat flux ha...
Latent heat
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In meteorology, lee waves are atmospheric stationary waves. The most common form is mountain waves, which are atmospheric internal gravity waves. These were discovered in 1933 by two German glider pilots, Hans Deutschmann and Wolf Hirth, above the Krkonoše. They are periodic changes of atmospheric pressure, temperature...
Lee wave
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They can also be caused by the surface wind blowing over an escarpment or plateau, or even by upper winds deflected over a thermal updraft or cloud street. The vertical motion forces periodic changes in speed and direction of the air within this air current.
Lee wave
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They always occur in groups on the lee side of the terrain that triggers them. Sometimes, mountain waves can help to enhance precipitation amounts downwind of mountain ranges. Usually a turbulent vortex, with its axis of rotation parallel to the mountain range, is generated around the first trough; this is called a rot...
Lee wave
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In meteorology, mixing ratio usually refers to the mass ratio of water ζ {\displaystyle \zeta } , which is defined as the mass of water m H 2 O {\displaystyle m_{\mathrm {H2O} }} divided by the mass of dry air ( m a i r − m H 2 O {\displaystyle m_{\mathrm {air} }-m_{\mathrm {H2O} }} ) in a given air parcel: ζ = m H 2 O...
Mixing ratio
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In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with wa...
Convectional Precipitation
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Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers.Moi...
Convectional Precipitation
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This process is typically active when freezing rain occurs. A stationary front is often present near the area of freezing rain and serves as the focus for forcing and rising air. Provided there is necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely...
Convectional Precipitation
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Eventually, the cloud droplets will grow large enough to form raindrops and descend toward the Earth where they will freeze on contact with exposed objects. Where relatively warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall becomes a concern downwind of the warm lakes ...
Convectional Precipitation
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Thundersnow is possible within a cyclone's comma head and within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation. On the leeward side of mountains, desert climates can exist due to the dry air caused...
Convectional Precipitation
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Most precipitation occurs within the tropics and is caused by convection. The movement of the monsoon trough, or intertropical convergence zone, brings rainy seasons to savannah regions. Precipitation is a major component of the water cycle, and is responsible for depositing fresh water on the planet.
Convectional Precipitation
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Approximately 505,000 cubic kilometres (121,000 cu mi) of water falls as precipitation each year: 398,000 cubic kilometres (95,000 cu mi) over oceans and 107,000 cubic kilometres (26,000 cu mi) over land. Given the Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres (39 in), b...
Convectional Precipitation
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Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Global warming is already causing changes to weather, increasing precipitation in some geographies, and reducing it in others, resulting in additional extr...
Convectional Precipitation
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In meteorology, prevailing wind in a region of the Earth's surface is a surface wind that blows predominantly from a particular direction. The dominant winds are the trends in direction of wind with the highest speed over a particular point on the Earth's surface at any given time. A region's prevailing and dominant wi...
Prevailing wind
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In the mid-latitudes, westerly winds are dominant, and their strength is largely determined by the polar cyclone. In areas where winds tend to be light, the sea breeze/land breeze cycle is the most important cause of the prevailing wind; in areas which have variable terrain, mountain and valley breezes dominate the win...
Prevailing wind
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Wind roses are tools used to display the direction of the prevailing wind. Knowledge of the prevailing wind allows the development of prevention strategies for wind erosion of agricultural land, such as across the Great Plains. Sand dunes can orient themselves perpendicular to the prevailing wind direction in coastal a...
Prevailing wind
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Insects drift along with the prevailing wind, but the flight of birds is less dependent on it. Prevailing winds in mountain locations can lead to significant rainfall gradients, ranging from wet across windward-facing slopes to desert-like conditions along their lee slopes. Prevailing winds can vary due to the uneven h...
Prevailing wind
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In meteorology, rapid intensification is a situation where a tropical cyclone intensifies dramatically in a short period of time. The United States National Hurricane Center defines rapid intensification as an increase in the maximum sustained winds of a tropical cyclone of at least 30 knots (35 mph; 55 km/h) in a 24-h...
Rapid intensification
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In meteorology, station models are symbolic illustrations showing the weather occurring at a given reporting station. Meteorologists created the station model to fit a number of weather elements into a small space on weather maps. This allows map users to analyze patterns in atmospheric pressure, temperature, wind spee...
Wind barb
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In meteorology, the 'therefore' sign is used to indicate 'moderate rain' on a station model; the similar typographic symbol asterism (⁂, three asterisks) indicates moderate snow.
Thus symbol
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In meteorology, the Coandă effect theory has also been applied to some air streams flowing out of mountain ranges such as the Carpathian Mountains and Transylvanian Alps, where effects on agriculture and vegetation have been noted. It also appears to be an effect in the Rhone Valley in France and near Big Delta in Alas...
Coandă Effect
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In meteorology, the different types of precipitation often include the character, formation, or phase of the precipitation which is falling to ground level. There are three distinct ways that precipitation can occur. Convective precipitation is generally more intense, and of shorter duration, than stratiform precipitat...
Convective precipitation
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Orographic precipitation occurs when moist air is forced upwards over rising terrain and condenses on the slope, such as a mountain. Precipitation can fall in either liquid or solid phases, is mixed with both, or transition between them at the freezing level. Liquid forms of precipitation include rain and drizzle and d...
Convective precipitation
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Rain or drizzle which freezes on contact with a surface within a subfreezing air mass gains the preceding adjective "freezing", becoming the known freezing rain or freezing drizzle. Slush is a mixture of both liquid and solid precipitation. Frozen forms of precipitation include snow, ice crystals, ice pellets (sleet), ...
Convective precipitation
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In meteorology, the equilibrium level (EL), or level of neutral buoyancy (LNB), or limit of convection (LOC), is the height at which a rising parcel of air is at the same temperature as its environment. This means that unstable air is now stable when it reaches the equilibrium level and convection stops. This level is ...
Equilibrium level
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In meteorology, the planetary boundary layer (PBL), also known as the atmospheric boundary layer (ABL) or peplosphere, is the lowest part of the atmosphere and its behaviour is directly influenced by its contact with a planetary surface. On Earth it usually responds to changes in surface radiative forcing in an hour or...
Planetary boundary layer
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In meteorology, the polar front is the weather front boundary between the polar cell and the Ferrel cell around the 60° latitude, near the polar regions, in both hemispheres. At this boundary a sharp gradient in temperature occurs between these two air masses, each at very different temperatures.The polar front arises ...
Polar front
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Off the coast of eastern North America, especially in winter, there is a sharp temperature gradient between the snow-covered land and the warm offshore currents. The polar front theory says that mid-latitude extratropical cyclones form on boundaries between warm and cold air. In winter, the polar front shifts towards t...
Polar front
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In meteorology, the polar highs are areas of high atmospheric pressure, sometimes similar to anticyclones, around the north and south poles; the south polar high being the stronger one because land gains and loses heat more effectively than sea, which the north has much less of. The cold temperatures in the polar regio...
Polar High
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This convergence of rising air completes the vertical cycle around the polar cell in each latitudinal hemisphere's polar region. Closely related to this concept is the polar vortex, a rotating low-pressure circle of cold air around the poles. Surface temperatures under the polar highs are one of the coldest on Earth, w...
Polar High
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In meteorology, the synoptic scale (also called the large scale or cyclonic scale) is a horizontal length scale of the order of 1,000 km (620 mi) or more. This corresponds to a horizontal scale typical of mid-latitude depressions (e.g. extratropical cyclones). Most high- and low-pressure areas seen on weather maps (suc...
Synoptic scale
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Most precipitation areas occur near frontal zones. The word synoptic is derived from the Ancient Greek word συνοπτικός (sunoptikós), meaning "seen together".
Synoptic scale
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The Navier–Stokes equations applied to atmospheric motion can be simplified by scale analysis in the synoptic scale. It can be shown that the main terms in horizontal equations are Coriolis force and pressure gradient terms; therefore, one can use geostrophic approximation. In vertical coordinates, the momentum equatio...
Synoptic scale
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In meteorology, the term vapor pressure means the partial pressure of water vapor in the atmosphere, even if it is not in equilibrium. This differs from its meaning in other sciences. According to the American Meteorological Society Glossary of Meteorology, saturation vapor pressure properly refers to the equilibrium v...
Saturation pressure