Accuracy of satellite total column ozone measurements in polar vortex conditions: Comparison with ground-based observations in 1979-2013

This study presents the first detailed long-term analysis of satellite and ground-based Dobson, Brewer, SAOZ (Système D'Analyse par Observations Zénithales) and DOAS (Differential Optical Absorption Spectrometer) measurements inside the Antarctic vortex for the 1979-2013 period. In general, the satellite measurements show a good agreement with ground-based measurements at all stations (correlation coefficient > 0.95). The average relative difference between ground-based and satellite measurements is about ±1-3% and the mean bias error (MBE) is within ±4 DU, depending on the satellite instrument and ground-based station. The satellite measurements show good stability over their operational period, for which the estimated drifts are about ±0.1-5%/decade and are statistically insignificant for most instruments. The Nimbus TOMS (Total Ozone Monitoring Spectrometer) and OMI (Ozone Monitoring Instrument) measurements are stable over the period, but the Earth Probe-TOMS measurements show deterioration after 2000. Also, most satellite instruments show no dependency on satellite solar zenith angle (SZA), but reveal significant dependency on stratospheric temperature. In addition, the mean relative difference shows larger variation with lower total column ozone (TCO). This long-term and multi-instrument comparison exercise would help both ground-based and satellite measurement community to better analyse accuracy of the TCO measurements from the instruments and examine the stability of their long-term measurements. In addition, the SZA and temperature dependency assessment would also help the ozone observation community to use better absorption cross-sections for TCO retrievals.