What kind of process does the atmospheric air undergo from a cool morning to a warm afternoon, assuming that the air composition and the velocity do not change, and also that no pressure from motion occurs during the day?

Assuming that air composition and velocity don't change the air near the surface get cooled during the morning hours as heat exchange take place.

Explanation:

The takes place due to the earth radiates heat as black body at the night time and while some energy is absorbed by the water bodies that release this energy to the land mass as the water cools faster at night the air above the water bodies moves to the landmass and the similar effects of the mountain and the valley breezes that move down and exchanges the heat from the land and morning hours the dew is found on the parts of plants which shows the process of cooling taking place.