Question

The rainfall decrease or increase as we go from South to North on earth.

Answer 1

The rainfall decreases from east to west in northern India because of the following reason:

The inflow of the south-west monsoon into India is such that the windward side of the Western Ghats receives very heavy rainfall, more than 250 cm. The rain shadow region receives scanty rainfall and the moisture laden clouds shed the maximum rainfall of this season in the north-eastern part of the country. Thus, Mawsynram in the southern ranges of the Khasi Hills receives the highest average rainfall in the world. Rainfall in the Ganga valley decreases from the east to the west. Hence, Rajasthan and parts of Gujarat which are on the western get scanty rainfall.

Answer 2

The rainfall decreases as we move South or North on earth because we move away from Equator.

As in equtor rainfalls there every evening  and when we move away from equtor to north or south of the earth the amount of rainfall decreases..

Hope it helps...