air mass


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air mass,

large body of air within the earth's atmosphereatmosphere
[Gr.,=sphere of air], the mixture of gases surrounding a celestial body with sufficient gravity to maintain it. Although some details about the atmospheres of other planets and satellites are known, only the earth's atmosphere has been well studied, the science of
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 in which temperature and humidity, although varying at different heights, remain similar throughout the body at any one height. Air masses form over parts of the earth's surface called source regions, which are large bodies of water or landmasses with relatively uniform topography, often ranging hundreds of thousands of square miles in area. When a body of air remains over a source region for days or weeks, it reaches an equilibrium with the surface. Radiation and convection exchanges between the surface and the air determines the air mass characteristics. Air masses formed over oceans generally contain more moisture than continental ones; air masses formed in polar latitudes are colder than those from the tropics. As an air mass moves away from its source region, it brings its particular weatherweather,
state of the atmosphere at a given time and place with regard to temperature, air pressure (see barometer), wind, humidity, cloudiness, and precipitation. The term weather
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 conditions to areas over which it travels. At the same time, its characteristic properties are slowly modified by exposure to new environments. The boundaries between air masses, called frontsfront,
in meteorology, zone of transition between adjacent air masses. If a cold air mass is advancing to replace a warmer one, their mutual boundary is termed a cold front; if the reverse, then the boundary is termed a warm front, whereas a stationary front indicates that no
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, are, typically, zones of rapid transition from cold to warm or from dry to moist air. Turbulence at the boundary often breeds low-pressure storms.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/

air mass

[′er ‚mas]
(meteorology)
An extensive body of the atmosphere which approximates horizontal homogeneity in its weather characteristics, particularly with reference to temperature and moisture distribution.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

air mass

A body of air with nearly uniform conditions of temperature and humidity at any given level.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
The fast-building nature of air mass thunderstorms can present challenges, especially when several storms are developing in a general area and the space between cells is at play.
Air mass thunderstorms are a catch-all phrase for the classic summertime "popcorn storm" that develops when there's a warm, humid air mass and the charts show no fronts or other focusing mechanisms.
This air mass is mostly just another form of polar maritime air, however it has a longer sea track that initially takes the air southwards over the North-Atlantic, then north-eastwards across the UK.
The length (L), lifetime (T), and depth of the cold air mass (H) associated with each density current are estimated from the simulations.
In order to find the minimum system capacity at a given operating condition, i, the air mass flow rates, temperatures, and humidity ratios for all zones must be optimized simultaneously such that [Q.sub.i.sup.req] is minimized:
Navigator Kevin Gamier had a hunch the high-pressure system would linger and, given the sailing properties of the J boat, the team had a better chance looping down around the heavy air mass and picking up the wind flowing out of it.
Heavy snow is likely to hit the Sea of Japan coast from northern Japan to the Chugoku region Monday due to a strong cold air mass over the Japanese archipelago, the Japan Meteorological Agency said.
Wide areas of the Japanese archipelago experienced the coldest temperatures so far this season Wednesday morning, as a cold air mass swept the islands, the Meteorological Agency said.
This approach uses data from air mass balancers, real-time air contaminant profiles, area samples and tracer gas simulations of contaminant dispersion to form a composite picture of ventilation conditions.
But after receiving the stitches, the pontiff arrived on time for an open- air mass for 350,000 in the city of Sandomierz, with a bandage visible just below his skullcap.
The last column in this table, [DELTA] Air Mass, is the air mass of 62 [xi] -Cyg subtracted from the air mass of NGC 7027.