What happens to air masses as they descend in the Hadley cell?

As air masses descend in the Hadley cell, they experience an increase in temperature and a decrease in moisture. This occurs because as the air descends, it is compressed by the increasing atmospheric pressure at lower altitudes. This compression causes the air to warm up. Additionally, the descending air is typically associated with high-pressure systems, which are characterized by clear skies and dry conditions. Since the air is descending and warming, it also has a reduced capacity to hold moisture, leading to a loss of humidity.

This process contributes to the arid conditions often found in regions around 30 degrees north and south of the equator, such as the deserts near the Tropics of Cancer and Capricorn. Thus, the correct answer highlights the key dynamics of air movement and moisture changes within the Hadley cell.