Suppose that the surface air on the windward side of a mountain rises and descends on the leeward side.

Suppose that the surface air on the windward side of a mountain rises and descends on the leeward side. Recall from Chapter 4 that the dew-point temperature is a measure of the amount of water vapor in the air. Explain, then, why the relative humidity of the descending air drops as the dew-point temperature of the descending air increases.