Air masses encountered in the Southern  Hemisphere differ little from their counterparts in the Northern Hemisphere. Since the greater portion of the Southern Hemisphere is oceanic, it is not surprising to find maritime climates predominating in that hemisphere.

The two largest continents of the Southern Hemisphere (Africa and South America) both taper from the equatorial regions toward the South Pole and have small land areas at high latitudes. Maritime polar air is the coldest air mass observed over the middle latitudes of the Southern Hemisphere.

In the interior of Africa, South America, and Australia, CT air occurs during the summer. Over the remainder of the Southern Hemisphere, the predominating air masses are mP, mT, and E air. The structure of these air masses is almost iden-tical with those found in the Northern Hemisphere.

Learning Objective: Define air mass classification and describe how the classification will change when characteristics modify.

Air masses are classified according to geographic source region, moisture content, and thermodynamic process.

The geographical classification of air masses, which refers to the source region of the air mass, divides air masses into four basic categories: arc-tic or antarctic (A), polar (P), tropical (T), and equatorial (E). An additional geographical classification is the superior (S) air mass. The superior air mass is generally found aloft over the southwestern United States, but is sometimes located at or near the surface.

The arctic (A), polar (P), and tropical (T) classifications are further broken down by moisture content. An air mass is considered to be maritime (m) if its source of origin is over an oceanic surface. If the air mass originates over a land surface, it is considered continental (c). Thus, a moist, maritime arctic air mass is designated m; and a drier, continental arctic air mass is designated c.

Equatorial (E) air is found exclusively over the ocean surface in the vicinity of the equator and is designated neither c nor m but simply E.

Table 4-1-1.Classification of Air Masses

[ Back ] [ Home ] [ Up ] [ Next ]

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing