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Validation of different configurations of the GODFIT/GDP5 algorithm using ground-based total ozone data

MariLiza Koukouli(1), Jean-Christopher Lambert(2), Dimitris Balis(1), Diego Loyola(3), Michel Van Roozendael(2), Christophe Lerot(2) and Jose Granville(2)

(1) Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece
(2) Belgian Institute for Space Aeronomy, , Brussels, Belgium
(3) German Aerospace Center (DLR), , Wessling, Germany


Total ozone estimates from different GODFIT/GDP5 configurations were compared with the current operational GOME GDP4 products and with ground based total ozone data from quality controlled Brewer, Dobson and SAOZ measurements available at WOUDC and NDACC in the frame of the project “GDP 5.0 - Upgrade of the GOME Data Processor for Improved Total Ozone Columns” funded by ESA. The different configurations concerning the total ozone retrieval algorithms include the use of different input temperatures (ECMWF or TOMS climatology with a retrieved temperature shift), different climatologies concerning the a priori ozone profiles (TOMS v8, various modes of NNORSY) and different schemes for cloud treatment (OCRA/ROCINN, FRESCO+). GOME retrievals using all possible combinations were compared with GDP4 products and with quality controlled ground-based total ozone estimates. The use of different combinations of the above apriori choices in the retrievals introduce marked deviation in the amplitude of the seasonal dependence of the differences between satellite and ground-based data, differences in the solar zenith angle dependence of the satellite retrievals and differences in their offset and latitudinal dependence. Irrespective of said differences in retrieval configuration, all GDP5 products are in better accord with the ground-based measurements for extreme cases such as high solar zenith angles, low stratospheric temperatures, low total ozone conditions, etc. than the respective GDP4.0 total ozone products.