Question

Why does the rainfall decrease from the east to west in Northern India?

Answer 1

because there are no tree in that area because of that there is less rainfall

Answer 2

because the south east winds enter our country from South and then due to rotation of earth it's direction is changes towards north east then winds move from east to west which reduces rainfall from east to west as
. mountain peeks are high in east so clouds collide there and shed most of their water in east
. in West peeks are low so clouds do not collide plus if it rains it pours very less due to less water in clouds...