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An air mass originating over northern Siberia in winter may be indicated as "cA". [3] The stability of an air mass may be shown using a third letter, either "k" (air mass colder than the surface below it) or "w" (air mass warmer than the surface below it). [3] An example of this might be a polar air mass blowing over the Gulf Stream, denoted as ...
A marine layer is an air mass that develops over the surface of a large body of water, such as an ocean or large lake, in the presence of a temperature inversion. The inversion itself is usually initiated by the cooling effect caused when cold water on the surface of the ocean interacts with a comparatively warm air mass. [1]
Larger fetches provide the boundary layer with more time to become saturated with water vapor and for heat energy to move from the water to the air. As the air mass reaches the other side of the lake, the engine of rising and cooling water vapor pans itself out in the form of condensation and falls as snow, usually within 40 km (25 mi) of the ...
(The total air mass below a certain altitude is calculated by integrating over the density function.) For the ocean example there was a sharp transition in density at the top or "surface" of the ocean. However, for atmospheres made of gas there is no equivalent sharp transition or edge.
Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. [ 1 ] : 162 As the air mass gains altitude it quickly cools down adiabatically , which can raise the relative humidity to 100% and create clouds and, under the right conditions, precipitation .
A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have arisen from the same cause, usually an orogeny. [1] Mountain ranges are formed by a variety of geological processes, but most of the significant ones on Earth are the result of plate tectonics . [ 2 ]
Precipitation occurs when evapotranspiration takes place and local air becomes saturated with water vapor, and so can no longer maintain the level of water vapor in gaseous form, which creates clouds. This occurs when less dense moist air cools, usually when an air mass rises through the atmosphere to higher and cooler altitudes.
The Bergeron classification is the most widely accepted form of air mass classification. Air mass classifications are indicated by three letters: [3] [4] Fronts separate air masses of different types or origins, and are located along troughs of lower pressure. [5] The first letter describes its moisture properties, with