An assessment of the world ground-based total ozone network performance from the comparison with satellite data

Total ozone data available from the World Ozone and Ultraviolet Radiation D ata Centre (WOUDC) have been compared with Version 7 of the Nimbus 7 (for t he 1978-1993 period) and Meteor 3 total ozone mapping spectrometer (TOMS) d ata sets (for the 1991-1994 period) and with Version 6 of the Nimbus 7 sola r backscattered ultraviolet (SBUV) data set (for the 1978-1990 period). Com parison between the ground-based and satellite observations resulted in par ameters such as bias, scattering, relative trend, and seasonal component. A bout 80% of all Dobson, Brewer, and filter ozonometer stations have standar d deviations of monthly mean differences with TOMS that are less than 2.5%. Typically, results of the comparisons between ground-based stations and SB UV are similar to those for ground-based and TOMS comparisons. For the grou nd-based direct sun total ozone measurements the standard deviations betwee n TOMS and Dobson daily mean values are about 2.4%. The standard deviations for Brewer and filter ozonometer stations are 2.2 and 3.5%, respectively. For the less accurate zenith sky measurements, standard deviations are 3.8% for Dobsons, 4% for Brewers, and 4.7% for filter ozonometer data. Comparis ons of individual ground-based measurements with satellite overpasses yield standard deviations which for middle latitudes increase approximately line arly from about 2% at coincidence to 6% for a 24 hour difference in time or a 600 km spatial difference. Typical problems with ground-based observatio ns and results of the comparisons for individual stations are also discusse d.