The land breeze is a coastal breeze at night blowing from the land to the ocean. It is caused by the difference in the rates of cooling of the land and of the ocean.At night land is relatively cold and hence at higher pressure and sea is relatively warm and at lower pressure .So cold air from land at higher pressure flow to surface of sea which is at lower pressure. Because air flows from higher pressure region to lower pressure region.
The picture has warm air over sea and cool air over land hence it is the process of land breeze.