In meteorology, an updraft is a small-scale current of rising air, often within a cloud.
Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region, and so will rise until it reaches air that is either warmer or less dense than itself. The converse will occur for a mass of cool air, and is known as subsidence. This movement of large volumes of air, especially when regions of hot, wet air rise, can create large clouds, and is the central source of thunderstorms. Drafts can also be conceived by low or high pressure regions. A low pressure region will attract air from the surrounding area, which will move towards the center and then rise, creating an updraft. A high pressure region will attract air from the surrounding area, which will move towards the center and sink, spawning a downdraft.
Updrafts and downdrafts, along with wind shear in general, are a major contributor to airplane crashes during takeoff and landing in a thunderstorm. Extreme cases, known as downbursts and microbursts can be deadly and difficult to predict or observe. The crash of Delta Air Lines Flight 191 on its final approach before landing at Dallas/Fort Worth International Airport in 1985 was presumably caused by a microburst, and prompted the Federal Aviation Administration (FAA) to research and deploy new storm detection radar stations at some of the major airports, notably the ones in the South, Midwest, and Northeast United States where wind shear affects air safety. Downbursts can cause extensive localized damage, similar to that caused by tornadoes. Downburst damage can be differentiated from that of a tornado because the resulting destruction is circular and radiates away from the center. Tornado damage radiates inward, towards the center of the damage.
The term downdraft can also refer to a type of backdraft which occurs through chimneys which have fireplaces on the lowermost levels (such as basements) of multi-level buildings.
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Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth. 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 (Coriolis effect).
In meteorology, a virga, also called a dry storm, is an observable streak or shaft of precipitation falling from a cloud that evaporates or sublimates before reaching the ground. A shaft of precipitation that does not evaporate before reaching the ground is a precipitation shaft. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is often due to compressional heating, because the air pressure increases closer to the ground.
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-velocity winds circle a central area, and air moves inward and upward. These usually last for seconds to minutes.
Explores the large-scale dynamics of the mid-latitude atmosphere, covering topics such as momentum conservation, jet streams, weather fronts, and cyclones.
In this thesis, we explore the best practice of simulating the wakes of the turbines under active yaw control (AYC) using large-eddy simulation (LES). In the first study, we validate the blade-element actuator disk model (ADM-BE) for a yawed wind turbine. ...
EPFL2023
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This study investigated the power production and blade fatigue of a three-turbine array subjected to active yaw control (AYC) in full-wake and partial-wake configurations. A framework of a two-way coupled large eddy simulation (LES) and an aeroelastic blad ...
The southeastern Atlantic (SEA) and its associated cloud deck, off the west coast of central Africa, is an area where aerosol–cloud interactions can have a strong radiative impact. Seasonally, extensive biomass burning (BB) aerosol plumes from southern Afr ...