The total ozone maps are based on ground-based
measurements available from the
World Ozone and Ultraviolet Radiation Data Centre. Preliminary near
real-time data from ground-based observations were also used for the most
recent maps. 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.
Maps of deviations represent total ozone
deviations from the
1978-1988 level estimated using
Total Ozone Mapping Spectrometer (TOMS) data for all areas except the
Antarctic and from the pre-1980 level estimated using Dobson data over the
Antarctic.
Over areas with poor data coverage adjustments
are made according to TOMS on
Nimbus-7, Meteor-3, ADEOS and Earth Probe satellites. 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. The mapping algorithm is similar to those used by the
WMO Ozone Mapping Centre. |