Micro Life Zone
Asked by awesomegal03 to Simon, Blaire, Jenny on 21 Mar 2013. This question was also asked by cheesecake.
Keywords: earth, google, how, wind
Simply put, wind is the motion of air molecules. Air is a combination of molecules; nitrogen (about 78 percent by volume), oxygen (about 21 percent by volume), water vapor (between 1 and 4 percent by volume near the surface of the earth) and other trace elements. All of these air molecules are moving about very quickly, colliding with each other. Air pressure is the amount of force that these molecules cause in a given area. The more air molecules present, the greater the air pressure. Wind is driven by changes in air pressure; air molecules from an area of high air pressure will rush to an area of low pressure.
Tornadoes are great examples. Scientists have placed scientific probes in the direct path of huge tornadoes and found that the air pressure drops by up to 10 percent within the tornado!
Differences in air pressure are caused by unequal heating of the Earth’s surface by the sun. As a local example think of a sea breeze. During the day the land heats faster than the water. The air over the land heats and rises and the cooler air over the water rushes inland. During the night the land cools faster than the water resulting in a reversal of the wind. On a global scale the wind is driven by unequal heating all over the earth. Here is a link that describes the formation and wind patterns caused by the unequal heating of the Earth’s surface:
Jennifer has done a great job explaining this.
I will add just one thing.
If the earth didn’t spin then the differential heating would create a big conveyor belt from the poles to the equator. Air warmed at the equator would go up, travel towards the poles, be cooled and sink, only to be pullled towards the equator again. All driven by the differential heating. BUT the earth is spinning. so as the air moves towards the equator the earth moves underneath it (momentum of the air) friction gradually turns the air aside and giant vortices are set up, we call them highs and lows in the weather forcecasts. Trying to work out what they are doing is what makes weather forecasts interesting.
By BRIDGE8 under license from Mangorolla CIC 2021