Total Ozone Trend Patterns from a Homogenized European Satellite Sensor Data Base
Coldewey-Egbers, Melanie¹; Loyola, Diego¹; van Roozendael, Michel²; Zimmer, Walter¹; Lerot, Christophe²; Dameris, Martin¹; Braesicke, Peter^3
1German Aerospace Center, GERMANY; ²BIRA-IASB, BELGIUM; ³University of Cambridge, UNITED KINGDOM

Global total ozone measurements from three European satellite sensors GOME/ERS-2, SCIAMACHY/ENVISAT, and GOME-2/MetOp-A were used in this study to analyse stratospheric ozone variability and decadal trends from global to regional scales.

Within ESA's Ozone Climate Change Initiative the satellite observations were merged into a 16 years high-quality data record called "GOME-type Total Ozone - Essential Climate Variable" (GTO-ECV), which covers the period June 1995 to June 2011. The merging approach accounts for inter-satellite biases and drifts in order to generate a stable, consistent and homogeneous long-term time series, which is a key requirement for monitoring climate change and in particular for the detection of expected small trends in ozone as a result of the 1987 Montreal Protocol. A second aspect of GTO-ECV is the evaluation of Chemistry-Climate Model (CCM) simulations to improve future ozone projections.
GTO-ECV monthly mean ozone anomalies indicate an excellent agreement with another well-established satellite-based merged ozone data record provided by National Aeronautics and Space Administration (NASA).

A multiple linear least-squares regression algorithm has been applied to the monthly mean 5° x 5° gridded data from 60°N to 60°S in order to analyse the regional influence of several atmospheric parameters such as the solar signal, the quasi-biennial oscillation, halogen loading, and also important climate indices on ozone variability. Linear ozone trend estimates as a function of latitude and longitude are presented for both, GTO-ECV and NASA satellite data sets and they indicate positive values (which are statistically significant at the 95% confidence level) in the tropics and northern mid latitudes with distinct longitudinal dependence. Positive trends found over Europe are confirmed with Brewer and Dobson ground-based observations.

Furthermore two CCM simulations provided by German Aerospace Center and University of Cambridge were compared and analysed with regard to long-term ozone changes.