Ok, so it’s a little late in the year to be going to the beach but I just can’t resist the salty charms of the seaside! I love feeling the sand between my toes, hearing the gentle crashing of the waves and feeling the wind in my hair. Well, actually most of the time the wind is really unnecessary. It’s not like we very often get to sunbathe and it gets so hot we’re glad for a breeze. But that doesn’t matter to the weather!
It’s always windy at the beach, even when it’s quite calm inland, because of the way that air moves when it gets hot. In the daytime the sun heats the land up faster than it heats the water up. This in turn heats the air above the land. Hot air is lighter than colder air since the molecules are moving faster, making it less dense, so it rises. Cold air from out to sea then rushes in to fill this gap.
As evening falls and the sun starts to lose its heat, the opposite happens. The land cools down a lot faster than the water, so now it’s the warm air out to sea that rises. This creates a breeze in the other direction.
This is an example of convection, which is the way that hot areas of gases and liquids move around. This all happens because of a change in density as the molecules get warmer, as well as the need to keep the space all filled up – there can’t be any unfilled space!