If you were to measure temperature of the air directly above each surface, which one, sand or water, would be warmest?
Why is it desirable for cities in warm climates to be located near large bodies of water?
It would depend on what time of day you do the measuring. Sand heats up quicker than water does, so if you measure at the end of the day, when the sun has been shining all day, the air over the sand will be warmer. If you meaure in the early morning, the air over the water will be warmer, because the sand gave up its energy during the night. This is how land breezes and sea breezes work. If you are at the beach during the day, the air over the water is cooler and comes rushing ashore, much the same as the waves roll in. This is called a sea breeze, named for the direction from which the breeze comes from. The air is cooler, and therefore more dense, so it pushes the warmer air over the land out of the way. At night, the land gives up its heat quicker than the water, so the air over the land becomes cooler and more dense. This is called a land breeze, as the air over the land pushes back out to sea.