Air – masses are classified on the following two basis:
1. The nature of the origin area.
2. Conversion of the air – mass.
On the basis of the nature of their area of origin, there are two types of air – masses: the tropical and the polar air – mass. Since the origin area can be either oceans or continents, therefore they can be divided into two sub – classes: sea tropical, continental tropical, sea-polar and continental polar. Due to high humidity in the sea air – masses, they cause excessive rainfall. In contrast, continental air – masses are dry and therefore they cause less rainfall.
