This is primarily because the sun heats the earth's surface unevenly. As heat is trans- ferred to the air, we get regions of warm and cool air which can turn into regions of low and high pressure. This difference in pres- sure makes a force that causes the wind to blow.
So I would say the rising of warm air and the falling of cool air.
<span>Much of the commercially important waterways of the United States consist of the Mississippi River System—the Mississippi River and connecting waterways. .... States on the Gulf Coast and throughout the Midwest and Ohio Valley ...</span>
