Does the amount of water vapor in the atmosphere vary?
The amount of water vapor in the atmosphere can vary significantly by location. The diagram below illustrates this. The red regions have greater than 60 mm of water in a column of atmosphere, while the blue and purple regions have less than 25 mm. http://www.wmo.ch/web/sat/en/ap8-06.htm Following are some of the reasons which explain the extremes in the diagram above, listed from most important to least important. Solar energy from the sun is the key driver for evaporation. By adding heat to a body of water, its temperature will increase and some water will evaporate. Because solar energy is more intense at the equator, there tends to be more water vapor in the atmosphere near the equator. It is of course necessary to have a body of water in order to have evaporation; this is why there is a lot of water vapor over the oceans, but less over land. Movement of frontal systems from bodies of water is a key cause of high humidity over land. For example, air masses from the Gulf of Mexico ca
