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doi:10.5194/amt-2016-139
© Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License. |
Research article
03 Jun 2016
1Deutsches Zentrum für Luft- und Raumfahrt, Münchener Strasse 20, 82234 Oberpfaffenhofen, Germany
2Royal Meteorological Institute, Avenue Circulaire 3, 1180 Brussels, Belgium
3Royal Belgian Institute for Space Aeronomy, Ringlaan 3, 1180 Brussel, Belgium
Received: 21 Apr 2016 – Accepted: 27 May 2016 – Published: 03 Jun 2016
Abstract. In preparation of the TROPOMI/S5P launch in autumn 2016 a tropospheric ozone retrieval based on the convective cloud differential method was developed. For intensive tests we applied the algorithm to the total ozone columns and cloud data of the satellites GOME, SCIAMACHY, OMI, GOME-2A and GOME-2B. Thereby a time series of 20 years (1995–2015) of tropospheric ozone columns was retrieved. To have a consistent total ozone data set for all sensors one common retrieval algorithm, namely GODFITv3, has been applied to all sensors and the L1 reflectances have also been soft calibrated. These data were input into the tropospheric ozone retrieval. However, the Tropical Tropospheric Ozone Columns (TTOC) for the individual instruments still showed small differences and therefore we harmonised the data set. For this purpose a multi-variant function was fitted to the averaged difference between SCIAMACHY's TTOC and those from the other sensors. The original TTOC was corrected by the fitted offset. GOME-2B data were corrected relative to the harmonised data from OMI and GOME-2A. The harmonisation leads to a better agreement between the different instruments. Also a direct comparison of the TTOCs in the overlapping periods proves that GOME-2A agrees much better with SCIAMACHY after the harmonisation. The improvements for OMI were small. The GOME and SCIAMACHY data overlap for one year for the complete tropics, this turned out to be insufficient to extrapolate back until 1995. Based on the harmonised observations, we created a merged data product, containing the TTOC from July 1995 to Dec. 2015. A first application of this 20 years record is a trend analysis. The global tropical trend is 0.75 ± 0.12 DU decade−1. Regionally the trends reaches up to 1.8 DU decade−1 like on the African Atlantic coast, over the Western Pacific the tropospheric ozone declined over the last 20 years with up to 0.8 DU decade−1. The tropical tropospheric data record will be extended in the future with the TROPOMI/S5P data, where the TTOC is part of the operational products.
Citation: Heue, K.-P., Coldewey-Egbers, M., Delcloo, A., Lerot, C., Loyola, D., Valks, P., and van Roozendael, M.: Trends of tropical tropospheric ozone from twenty years of European satellite measurements and perspectives for Sentinel-5 Precursor, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-139, in review, 2016.
2Royal Meteorological Institute, Avenue Circulaire 3, 1180 Brussels, Belgium
3Royal Belgian Institute for Space Aeronomy, Ringlaan 3, 1180 Brussel, Belgium
Citation: Heue, K.-P., Coldewey-Egbers, M., Delcloo, A., Lerot, C., Loyola, D., Valks, P., and van Roozendael, M.: Trends of tropical tropospheric ozone from twenty years of European satellite measurements and perspectives for Sentinel-5 Precursor, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-139, in review, 2016.
