meteorology Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...

, an updraft is a small-scale

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

of rising

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...

, often within a

cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may co ...

Overview

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 Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...

. This movement of large volumes of air, especially when regions of hot, wet air rise, can create large

s, and is the central source of

thunderstorms A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are somet ...

. 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 Wind shear (or windshear), sometimes referred to as 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 either vertical or horizontal ...

in general, are a major contributor to airplane crashes during takeoff and landing in a thunderstorm. Extreme cases, known as

downburst 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 pro ...

s and microbursts can be deadly and difficult to predict or observe. The crash of

Delta Air Lines Flight 191 Delta Air Lines Flight 191 was a regularly scheduled Delta Air Lines domestic service from Fort Lauderdale, Florida, to Los Angeles with an intermediate stop at Dallas/Fort Worth International Airport (DFW). On August 2, 1985, the Lockheed ...

on its final approach before landing at

Dallas/Fort Worth International Airport Dallas/Fort Worth International Airport , also known as DFW Airport, is the primary international airport serving the Dallas–Fort Worth metroplex and the North Texas Region in the U.S. state of Texas. It is the largest hub for American Air ...

in 1985 was presumably caused by a microburst, and prompted the

Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...

(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 Aviation safety is the study and practice of managing risks in aviation. This includes preventing aviation accidents and incidents through research, educating air travel personnel, passengers and the general public, as well as the design of airc ...

. Downbursts can cause extensive localized damage, similar to that caused by

tornado A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, altho ...

es. 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 A backdraft ( North American English) or backdraught (British English) is the abrupt burning of superheated gasses in a fire, caused when oxygen rapidly enters a hot, oxygen-depleted environment; for example, when a window or door to an enclosed ...

which occurs through chimneys which have fireplaces on the lowermost levels (such as basements) of multi-level buildings. It involves cold air coming down the chimney due to low air pressure, and makes it hard to light fires, and can push soot and

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

into domiciles.

References

External links

National Science Digital Library - Downdraft

{{Natural disasters Severe weather and convection Aviation meteorology

Overview

See also

References

External links