How much water vapor is in the atmosphere in tons?

Answer 1

According to the USGS and NOAA, a 1km³ cumulus cloud would weigh about 2.21 billion pounds, or about 1,105 tons (US). The same volume of dry air weighs about 2.22 billion pounds, which is why clouds float. Because it is less dense than air, in truth, it doesn't "weigh" anything. It has volume. If you sucked all the water vapor out of the air and put it in a bucket, though, using the below chart as a guide and the fact that water is 1kg per liter, and one liter of water is 0.1 cubic meters, you'd have 12,900,000,000 liters of water, which is 12.9 trillion kg. (It's enough to cover the earth's 510,072,000 km² surface with about 25mm of water. Because the earth's average rain fall is about 1 meter, you can figure that all of this water vapor is recycled every nine or ten days.) So, to convert that metric to US tons and answer your question, all of that means that there is approximately more than 14.2 billion US tons of water vapor in the atmosphere.

Water sourceWater volume, in cubic milesWater volume, in cubic kilometersPercent of total freshwaterPercent of total waterAtmosphere3,09412,9000.04%0.001%Total global fresh water8,404,00035,030,000100%2.5%Total global water332,500,0001,386,000,000--100%Source: Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp.817-823.