Retrieval of Global Carbon Dioxide From TanSat Satellite and Comprehensive Validation With TCCON Measurements and Satellite Observations

To cope with global climate change and monitor global CO2 concentration distribution, the first Chinese carbon dioxide satellite (TanSat) has been successfully launched in December 2016. In this study, we implemented a CO2 retrieval scheme by calibrating the TanSat sun-glint (GL) mode spectra and adapting the Iterative Maximum A Posteriori Differential Optical Absorption Spectroscopy ( IMAP-DOAS) algorithm for CO2 spectral retrieval. The global terrestrial CO2 total vertical column density (VCD) and column-averaged dry-air mole fractions of CO2 (XCO2) were simultaneously retrieved from TanSat GL spectral observations. Then, a comprehensive verification was performed between TanSat CO2 retrieval and other measurements including Total Carbon Column Observing Network (TCCON), the Japanese Greenhouse gases Observing SATellite (GOSAT), and the US Orbiting Carbon Observatory-2 (OCO-2). Further comparisons between our TanSat CO2 retrieval and ground-based FTIR measurements from TCCON indicated a good correlation with the mean bias of -0.78 ppm, the standard deviation at 1.75 ppm, and the Pearson correlation coefficient of 0.81. In addition, cross-satellite CO2 validations of TanSat with GOSAT and OCO-2 showed consistently spatiotemporal trends for both CO2 VCD and XCO2. In summary, we can conclude that the presented CO2 retrieval scheme has achieved global CO2 retrieval from TanSat GL mode spectra with high precision and accuracy, as suggested by the results of independent ground-based and satellite validations.

Automated summary

In this study, a CO2 retrieval scheme using the Chinese TanSat satellite was implemented, achieving global CO2 detection with high precision and accuracy. The results were validated against ground-based and satellite measurements, showing a good correlation and consistent trends.