Maps of deviations represent total ozone deviations from the 1978-1988 level estimated using TOMS data. for all areas except the Antarctic, and from the pre-1980 level estimated using Dobson data over the Antarctic. The total ozone maps for the northern hemisphere are based on near-real time NASA Earth Probe Total Ozone Mapping Spectrometer (TOMS) gridded satellite data available from the NASA TOMS home page, NOAA SMOBA (Stratosphere Monitoring Ozone Blended Analysis) data (if TOMS data are not available) and on ground-based measurements. Ground-based data are provided by Environment Canada, by the Russian Central Aerological Observatory, and by other agencies. Over the polar night area Dobson and Brewer moon observations and/or NOAA’s TIROS Operational Vertical Sounder (TOVS) satellite data are used. TOVS data are also used when the more reliable TOMS data are not available. To see ozone maps from the individual data sources (TOMS, SMOBA, TOVS and ground-based) click here. The mapping algorithm is similar to those used by the WMO Ozone Mapping Centre . Total ozone values are given in Dobson Units.
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.
The numbers on the high resolution maps indicate total ozone values in Dobson Units measured at ground-based stations. Small symbols after the numbers indicate type of observation: the most reliable direct sun measurements have no symbols, less reliable observations from zenith sky light are marked by “z”. Focus moon observations during the polar night are marked by “+” symbol. All other types of measurements are marked by “*”. For more information on ground-based ozone measurements visit the WOUDC Web site.
WARNING: The data are processed in near real-time, have not been fully validated, and are preliminary.