Final answer:
Air mass modification is more rapid when the air mass flows over a surface that is warmer than the lowest layer of the air mass, because the underlying surface can change the temperature and moisture content of the air mass.
Step-by-step explanation:
As an air mass migrates from its source region, it begins to modify. Air mass modification is more rapid when the air mass flows over a surface (land or water body) that is b) Warmer than the lowest layer of the air mass. This is because the underlying surface can impart energy to the air mass, thereby changing its temperature and, in some cases, its moisture content more quickly. This concept is illustrated by several phenomena:
- Evaporation is greater in hot, sunny conditions, influencing the moisture content of an air mass over warm surfaces.
- When humid air rises over a mountain, it cools and condenses, leading to precipitation on the windward side and a drier rain shadow on the leeward side.
- The specific heat of land and water differ, with water taking longer to heat and cool, impacting the modification of air masses over these surfaces.
Moreover, coastal regions tend to have moderated climates due to the slower heating and cooling of water bodies, affecting adjacent air masses differently from those that migrate over land.