Retrievals of Total and Tropospheric Ozone From GOSAT Thermal Infrared Spectral Radiances

Total and tropospheric ozone columns have been retrieved from thermal infrared spectral radiances recorded with the Thermal And Near infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS), which is onboard the Greenhouse gases Observing SATellite launched on January 23, 2009. We present ozone retrievals that were performed over about two years of observations (during the period from April 2009 to December 2010) over four climatically distinct regions (the Sapporo, Tsukuba, Naha, and Syowa sites). Annual variations of the total and tropospheric ozone columns over the four sites were derived. We compare TANSO-FTS total ozone columns with ground-based data from the Dobson spectrophotometer, and the seasonal trends and patterns of the retrieved total ozone are consistent with those of Dobson measurements. The TANSO-FTS total ozone columns are in good agreement with the Dobson data, with a correlation coefficient of about 0.98. On average, TANSO-FTS total ozone retrievals exhibit a positive bias of 8.8 DU (3.0%) with a root-mean-square difference of 10.9 DU (4.1%) compared to the Dobson measurements. Comparisons of the TANSO-FTS tropospheric ozone columns to ozonesondes available from the four sites have been performed. The TANSO-FTS tropospheric ozone columns compare well with the ozonesonde measurements, with correlation coefficients of 0.96 and 0.92 for the surface-tropopause and surface-6 km partial columns, respectively. Average differences of 0.7 ± 4.2 DU (2.5% ± 12.8%) and -0.7 ±2.2 DU (-3.0% ±12.2%) are found for the surface-tropopause and surface-6 km partial columns, respectively.