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.

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.

air mass

A body of air with nearly uniform conditions of temperature and humidity at any given level.
References in periodicals archive ?
The polar air mass will deepen on Wednesday creating a tangible drop in mercury levels especially in the northern and central areas and the weather will be chilly and cloudy with rainfall accompanied with thunder and hail at times.
Besides, in association with cold air mass, it brought down temperature by eight degree Celsius, three to six degrees less than the monthly average of temperature in March", he said.
Forecaster Brian Gaze, of The Weather Outlook website, said: "This is an exceptionally warm air mass already for the time of year, and when high pressure moves east later in the week, even warmer air could be pumped up from the south.
It takes a combination of a cold air mass plus a moist air mass moving in at the same time to generate snow for Eugene and Springfield, and to what degree that will happen remains to be seen, the weather service said.
His itinerary will also include an address at Westminster Hall in the Houses of Parliament and the beatification of the 19th century Roman Catholic convert Cardinal John Henry Newman at an open air Mass at Coventry Airport.
Pope Benedict XVI is to start his four-day trip in Scotland on September 16 where he will be received by the Queen at Holyroodhouse in Edinburgh before travelling to Glasgow for an open air Mass at Bellahouston Park.
In the 1980s, the hot wire air-mass meter was developed to measure air mass using thermal measurement principles and was used in Formula 1 racing.
E is the energy transfer due to an air mass flow into or out of the zone (excluding mass flows due to infiltration).
A winter storm that was set to bear down on the Antelope Valley late Thursday and into this morning will be followed by an extreme cold air mass from the Sierra expected to bring potentially record-breaking temperatures this weekend, the National Weather Service said.
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.
We all thank St Luke's andSt Dominic's for the most fantastic open air mass held at the cemetery on July 3.
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.