Water has a high specific heat capacity compared to the land. During the day, sunshine raises the temperature of the land more than it raise the temperature of the water. The air over the land warms up and rises, starting convection currents that flow from the sea in towards the land. At night, water retains its warmth better than the land does, and the air over the water warms up and rises, starting convection currents that flow from the land out towards the sea.
Work Step by Step
This is discussed on page 306 and shown in Figure 16.8.