Question

Explain why a descending mass of air would tend to become drier

Answer 1

Descending mass of air would tend to become drier because lower down you come the warmer it gets, due to atmospheric pressure, so the relative humidity decreases which causes it to feel drier....
hope this helps!

Answer 2

The majority of the air molecules are concentrated near the earth's surface. Due to their tight arrangement near the surface, they experience more pressure, as a result of which it starts contracting and gets heated up. Whereas at the higher altitude region, there is a minimum amount of air molecules and are arranged in a scattered manner. So they undergo expansion and cools.

So, a descending air mass becomes drier as it reaches the earth's surface.