Lynn Marie Kasai, Age 9, Of Sarasota, Fla., For her question;

What determines wind direction?

The main cause of wind direction is air pressure. This is the weight or density of the atmosphere, and the atmosphere is a hodgepodge of vast masses of lighter and heavier air. This patchwork of different air masses is caused by the beaming sun which warms some parts of the globe more than others. The air gets its heat from the land and water upon which it rests.

In the main, heavy air tends to flow into masses of light air to even up the balance of atmospheric pressure. As a rule, the wind blows from the direction of a heavy air mass toward. A mass of lighter air.