Tropical tropospheric ozone columns from nadir retrievals of GOME-1/ERS-2, SCIAMACHY/Envisat, and GOME-2/MetOp-A (1996-2012)
Abstract. Tropical tropospheric ozone columns are retrieved with the Convective Clouds Differential (CCD) technique using total ozone columns and cloud parameters from different European satellite instruments. Monthly mean tropospheric column amounts [DU] are calculated by subtracting the above cloud ozone column from the total column. A CCD algorithm (CCD_IUP) has been developed (as part of the verification algorithm development for TROPOMI on Sentinel 5-precursor mission) which was applied to GOME/ ERS-2 (1995-2003), SCIAMACHY/ Envisat (2002-2012), and GOME-2/ MetOpA (2007-2012) measurements. Thus a unique long-term record of monthly mean tropical tropospheric ozone columns (20°S–20°N) from 1996 to 2012 is now available. An extensive error analysis has been performed, estimating the tropospheric ozone column uncertainties being between 5 and 7 DU (25–36%). Validation with SHADOZ ozonesonde data show that tropospheric ozone columns from CCD and collocated integrated ozonesonde profiles from the surface up to 200 hPa are in good agreement with respect to range, inter-annual variations, and variances. Biases within ±5 DU and RMS errors of less than 10 DU are found. CCD comparisons using SCIAMACHY data with tropospheric ozone columns derived from Limb Nadir Matching have shown that CCD results are less noisy and correlate better with ozonesondes. The 17-year dataset can be helpful for evaluating chemistry models and performing climate change studies.