The difference in how land and water surfaces absorb heat, with water having a higher heat capacity than land. The same amount of solar radiation will heat the same area of ground more than it will the ocean. The heat absorbed by the ocean will be distributed over a greater vertical extent than on land due to mixing in the water column. These factors lead to the difference between land and ocean temperatures being greatest in the summer when the amount of solar radiation is the highest, with the land being warmer than the ocean. In the winter the ocean surface is warmer than the land, although the differential isn’t as great as in winter. Diurnal variations in differential heating lead to the phenomenon known as a sea breeze, while long term (i.e. over weeks to months) variations lead to prevailing winds often called monsoons.