Why is the land breeze experienced at night? need an explanation related to the following diagram

Land breezes usually occur at night because during the day the sun will heat land surfaces, but only to a depth of a few inches. ... The movement of the wind is a result of differences in air pressure over the land and the ocean. Warm air is less dense and rises, therefore cool air is more dense and sinks. At night, the roles reverse. The air over the ocean is now warmer than the air over the land. ... This causes a small temperature gradient between the ocean surface and the nearby land at night and the wind will blow from the land to the ocean creating the land breeze.