Source Regions of Air Masses
The formation of air masses is usually associated with what are called source regions: regions of Earth’s surface that are particularly well suited to generate air masses. Such regions must be extensive, physically uniform, and associated with air that is stationary or anticyclonic.
Ideal source regions are – ocean surfaces and extensive flat land areas that have a uniform covering of snow, forest, or desert.
Air masses rarely form over the irregular terrain of mountain ranges.
Classification of Air Masses
Air masses are classified on the basis of source region. The latitude of the source region correlates directly with the temperature of the air mass, and the nature of the surface strongly influences the humidity content of the air mass. Thus,
A low-latitude air mass is warm or hot
A high-latitude one is cool or cold.
If the air mass develops over a continental surface, it is likely to be dry; if it originates over an ocean, it is usually moist. A one- or two-letter code is generally used to identify air masses. Although some authorities recognize other categories, the basic classification is sixfold are as follows:-
FRONTS
When unlike air masses meet, they do not mix readily; instead, a boundary zone called a front develops between them. A front is not a simple two-dimensional boundary. A typical front is a narrow three-dimensional transition zone several kilometers or even tens of kilometers wide. Within this zone, the properties of the air change rapidly.