The total ozone map is based on ground-based measurements by Brewer spectrophotometers carried out by the Science and Technology Branch. Total ozone values are given in Dobson Units. The numbers represent observations taken from ground stations situated at the bottom left corner of the number. The numbers marked by the “*” symbol are obtained using indirect method of measurements and are less reliable. The numbers on the maps indicate total ozone values in Dobson Units measured at ground-based stations. For more information on ground-based ozone measurements visit the WOUDC Web site.
Over areas with poor data coverage adjustments are made according to NASA’s Total Ozone Mapping Spectrometer (TOMS) on Earth Probe satellites. Over the polar night area Brewer moon observations and/or NOAA’s TIROS Operational Vertical Sounder (TOVS) data are used. TOVS data are also used when the more reliable TOMS data are not available. The mapping algorithm is similar to those used by the WMO Ozone Mapping Centre. Maps of deviations represent total ozone deviations from the 1978-1988 level estimated using TOMS data.
These maps are normally updated daily at about 1400 UTC. However, this near-real-time system is automated, so if a system problem occurs outside of regular working hours, it will not be fixed until the following work day.
WARNING: The data are processed in near real-time, have not been fully validated, and are preliminary.