Abstract
Abstract. Tropical tropospheric ozone columns are retrieved with the convective cloud 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 developed for TROPOspheric Monitoring Instrument (TROPOMI) on Sentinel 5-precursor (S5p) mission, which was applied to GOME/ERS-2 (1995–2003), SCIAMACHY/Envisat (2002–2012), and GOME-2/MetOp-A (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 uncertainty estimation has been performed, resulting in a tropospheric ozone column uncertainty less than 2 DU ( < 10 %) for all instruments. The dataset has not been yet harmonised into one consistent; however, comparison between the three separate datasets (GOME/SCIAMACHY/GOME-2) shows that GOME-2 overestimates the tropical tropospheric ozone columns by about 8 DU, while SCIAMACHY and GOME are in good agreement. Validation with Southern Hemisphere ADditional OZonesondes (SHADOZ) data shows that tropospheric ozone columns from the CCD_IUP technique and collocated integrated ozonesonde profiles from the surface up to 200 hPa are in good agreement with respect to range, interannual variations, and variances. Biases within ±5 DU and root-mean-square (RMS) deviation of less than 10 DU are found for all instruments. CCD comparisons using SCIAMACHY data with tropospheric ozone columns derived from limb/nadir matching have shown that the bias and RMS deviation are within the range of the CCD_IUP comparison with the ozonesondes. The 17-year dataset can be helpful for evaluating chemistry models and performing climate change studies.
Highlights
Stratospheric ozone is well known for protecting the surface from harmful ultraviolet solar radiation
Ozone is a secondary pollutant produced exclusively in the atmosphere with a flux of 3420 ± 770 Tg yr−1 (IPCC, 2007). It is mainly generated from the photochemical oxidation of four major precursors: carbon monoxide (CO), methane (CH4), volatile organic compounds (VOCs), and non-methane volatile organic compounds (NMVOCs) which are produced in the presence of nitrogen oxides (NOx = NO + NO2)
We present the results of our convective cloud differential (CCD) algorithm (CCD_IUP) using total ozone column (TCO) data retrieved with the WFDOAS (Coldewey-Egbers et al, 2005) algorithm applied on spectra from the series of European satellite instruments GOME, SCIAMACHY, and Global Ozone Monitoring Experiment-2 (GOME-2)/MetOp-A, spanning a time period of 17 years (1996–2012)
Summary
Stratospheric ozone is well known for protecting the surface from harmful ultraviolet solar radiation. Tropospheric ozone over the tropical Pacific presents a persistent minimum due to ozone loss reactions that are favoured by the specific conditions dominating there, such as the high marine boundary layer air temperature and the low overhead ozone. These conditions favour the strong advection from east to west by the Walker circulation. The present study focuses on the convective cloud differential (CCD) method which was first developed by Ziemke et al (1998) and applied to TOMS (1979–2005) and OMI ozone data (since 2004) (Ziemke and Chandra, 2012).
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