How to Calculate the Mass of the Air in the Atmosphere Earth's Shape: oblate spheroid Diameter polar = 12719 km Diameter equatorial = 12762 km Diameter average = 12740.5 km Atmosphere: 25 km Radius of Earth: (12740)/2 = 6370 km = 6.37x106 m Radius of Earth and air: (12740 + 50)/2 = 6395 km + 6.395x106m Volume of sphere formula: 4/3 pr3 Volume of Earth: 4/3 pr (6.37 x 106m)3 = 1.0827 x 1021m3 Volume of Earth and air: 4/3 p (6.395 x 106m)3 = 1.0959 x 1021m3 Note: 97% of the atmosphere's weight is found within 25 km of Earth's surface. Calculate the volume of air: Volume of Earth and air: 1.0959 x 1021m3 Volume of Earth: 1.0827 x 1021m3 Density = Mass/Volume Density x Volume = Mass Average Density of Air = = 0.450 kg/m3 or 450g/m3 Important Note: With the density/height variation in mind we used a density averaged over the whole atmospheric layer under consideration -- zero to 25 km in this case. The density of air drops by a factor of 30 between the surface and 25 km altitude. Calculate the mass of air: Density = 450g/m3 Volume = 1.28 x 1019m3 Mass = 5.76 x 1021g of Air Back to: Yellowstone Biomass Burning Activity Or choose from the following: Finding Carbon Released What is the gram molecular weight of the atmosphere? HTML code by Chris Kreger Maintained by ETE Team Last updated April 28, 2005 Some images © 2004 www.clipart.com Privacy Statement and Copyright © 1997-2004 by Wheeling Jesuit University/NASA-supported Classroom of the Future. All rights reserved. Center for Educational Technologies, Circuit Board/Apple graphic logo, and COTF Classroom of the Future logo are registered trademarks of Wheeling Jesuit University.