Ozone gas is a form of oxygen in which each molecule has three oxygen atoms instead of two. Near the ground, ozone is a pollutant that forms when byproducts of burning coal, oil, or gasoline mix with water vapor in the presence of sunlight. In the stratosphere, however, ozone forms naturally and absorbs harmful ultraviolet radiation known as UV-B. The Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite provides daily total-column ozone, which is how much ozone is present in a column of the atmosphere stretching from the surface to the top of the atmosphere. Therefore, it includes both ground-level and stratospheric ozone.These maps show monthly total-column ozone as measured by OMI from October 2004 to the present. Ozone concentrations are measured in Dobson Units. A Dobson Unit is the amount of ozone that would be required to create a layer of pure ozone 0.01 millimeters thick at the Earth’s surface, at a temperature of 0 degrees Celsius and a pressure of 1 atmosphere.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 220.127.116.11.0