The Erythemal Index is a measure of ultraviolet (UV) radiation at ground level on the Earth. (The word 'erythema' means an abnormal redness of the skin, such as is caused by spending too much time in the sun—a sunburn is damage to your skin cells caused by UV radiation.) Atmospheric ozone shields life at the surface from most of the harmful components of solar radiation. Chemical processes in the atmosphere can affect the level of protection provided by the ozone in the upper atmosphere. This thinning of the atmospheric ozone in the stratosphere leads to elevated levels of UV at ground level and increases the risks of DNA damage in living organisms.
This animation shows daily erythemal index for 2000-01-01 through 2001-12-31. Each days image is built up from observations taken near local solar noon; the western Pacific is measured near the beginning of the day (in Greenwich Mean Time - GMT), and the eastern Pacific is measured near the end of the GMT day. There is a 24-hour discontinuity in the data at 180th meridian. Diagonal bands with no data are areas that the satellite did not view on a particular day. The image size is 288x180 pixels (288x176 pixels for the MPEG movie); each pixel corresponds to an area 1 degree in longitude by 1.25 degrees in latitude.
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 22.214.171.124.0