WHY DESERT REMAIN DRY?

There are three possible reasons why desert remain dry. these are high mountain barriers, cold ocean currents, and high pressure system.
First is due to mountain barriers. when warm air passes over the ocean, it picks up moisture in the form of water vapor. as this moist air travels over the land, it rises to pass over mountain ranges. when it begins to raise, the air cools and this causes the water vapor to condense into droplets which fall as rain. when the air reaches the other side of the mountain barrier, it has lost all its moisture and so the other side of the mountain remains dry.
another reason is cold ocean currents. air passing over cold ocean currents is cooled, and therefore is unable to pick up and hold much moisture. when this cold air mass reaches the warm desert, any moisture in the air is evaporated and so does not fall as rain so the desertremains dry.
the last reason deals with high pressure systems. in ahigh pressure system, the air is dry and is moving downwards. as this system moves over the land surface. consequently, the moisture does not fall as rain and so the desert remains dry.

source : Santosa, Riyadi, M.Ed.dkk.2012. English For Academic Purposes.Surakarta : unspress.