In meteorology, an air mass is a volume of air defined by its temperature and water vapor content, which can cover many hundreds or thousands of square miles, and adopt the characteristics of the surface below them. Colder air masses are termed polar or arctic, while warmer air masses are deemed tropical. Weather fronts separate air masses. For example, a cold front indicates the leading edge of a colder air mass replacing a warmer air mass. Air masses have a classification and notation system. Theyre classified according to latitude and their source regions, which can be over ocean or land. The classification involves two letters. The first letter describes its moisture properties, with c used for continental air masses (dry and over land) and m for maritime air masses (moist and over the ocean). The second letter describes the temperature of its source region: T for tropical, P for polar, and A for arctic or antarctic. So for example, an air mass originating over the desert southwest of the United States in summer may be designated cT, while an air mass originating over the Bearing Sea in winter may be indicated as mA. Arctic air masses are very cold, colder than polar air masses. They are weaker in the summer but can strengthen and expand southward in the winter. Tropical air masses are hot since they develop at lower latitudes in the tropics. Those that develop over land (continental) are drier and hotter than those that develop over oceans, and travel northward during the summer.
Posted on: Sun, 11 Jan 2015 21:00:30 +0000
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