IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (Jan 2024)
Validation of Remotely Sensed XCO<sub>2</sub> Products With TCCON Observations in East Asia
Abstract
As an important greenhouse gas (GHG) in the atmosphere, carbon dioxide (CO2) has a great impact on global climate change. Accurate knowledge of the spatiotemporal variations of CO2 is of great significance for understanding the carbon cycle and evaluating the effectiveness of carbon emission reduction. In recent years, several satellites with CO2 sensors have been launched and a series of atmospheric CO2 concentration products have been developed using different retrieval algorithms. This study validated nine satellite XCO2 products derived from Greenhouse gases Observing SATellite (GOSAT), GOSAT-2, Orbiting Carbon Observatory-2 (OCO-2), and OCO-3: including ACOS-GOSAT, NIES-GOSAT, BESD-GOSAT, OCFP-GOSAT, SRFP-GOSAT, EMMA, GOSAT-2, OCO-2, and OCO-3 XCO2. The remotely sensed XCO2 products were compared with the XCO2 observations from six Total Carbon Column Observing Network (TCCON) stations in East Asia for validation. The results showed that the OCO-2 XCO2 product outperformed other products, with the highest R2 of 0.94 and the lowest MAE of 1.24 ppm. The ACOS-GOSAT and EMMA-GOSAT XCO2 products also showed favorable accuracies, both achieving R2 of 0.93 and corresponding MAE values of 1.29 and 1.31 ppm, respectively. The GOSAT-2 XCO2 product showed the poorest accuracy, with an R2 of 0.77 and a mean absolute error of 3.28 ppm. There was a significant overestimation of the bias-uncorrected GOSAT-2 XCO2 product in East Asia, and it indicated that bias correction must be performed for this XCO2 product. The accuracy of TCCON XCO2 was not consistent with remotely sensed XCO2 at different stations. The RJ, JS, AN, and TK TCCON stations generally showed better agreements between satellite estimates and TCCON observations, except for the GOSAT-2 XCO2 product.
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