ABSTRACT
In numerical weather prediction models and climate models the equations are used. The earth’s atmosphere is rather opaque to terrestrial radiation. Water vapour, carbon dioxide, methane etc., absorb and re-radiate terrestrial radiation. Atmospheric models calculate seasonal and diurnal as well as latitudinal variation of solar radiation, its scattering and reflection. They also calculate the absorption and re-radiation of terrestial radiation. The IITM earth system model model has atmosphere, land, sea-ice, ocean and interactive bio-geochemistry. The atmospheric part is a spectral general circulation model. The realistic monsoon southwesterly/ westerly winds over India and southeast Asia are very well reproduced. The turning of the southeast trades into monsoon winds can also be seen. The north Pacific and north Atlantic anticyclones can be noticed.
