Validation and assessment of satellite-based columnar CO2 and CH4 mixing ratios from GOSAT and OCO-2 satellites over India

作者：H. Gadhavi, Akanksha Arora, Chaithanya Jain, M. Sha, Frank Hase, M. Frey, Srikanthan Ramachandran, Achuthan Jayaraman · 发表于：Atmospheric Measurement Techniques · 年份：2025 · DOI：10.5194/amt-18-4497-2025 · 被引用次数：1

Abstract. Satellite observations of column-averaged carbon dioxide (XCO2) and methane (XCH4) mixing ratios provide essential data for monitoring greenhouse gas (GHG) emissions. However, the accuracy of emission estimates depends on the precision and bias of satellite retrievals, which require validation against ground-based reference measurements. This study presents a systematic validation of XCO2 and XCH4 data from GOSAT (Greenhouse gases Observing SATellite) and OCO-2 (Oribiting Carbon Observatory-2) satellites over South India using ground-based Fourier transform spectrometer (FTS) observations at Gadanki (13.5° N, 79.2° E) collected from October 2015 to July 2016. Satellite products from National Institute for Environmental Studies, Japan (NIES), NASA's Atmospheric CO2 Observations from Space (ACOS) project, USA (ACOS), and the University of Leicester, UK (UoL) were evaluated using a three-step spatial-temporal pairing method. Results show that the UoL's proxy XCH4 product meets the European Space Agency's Climate Change Initiative (ESA CCI) bias requirement (<10 ppb) across all spatial windows, while the NIES XCH4 product meets the requirement only for intermediate spatial scales. For XCO2, NASA ACOS and OCO-2 products meet the CCI bias requirement (<0.5 ppm), while NIES XCO2 exceeds this threshold. All products satisfy the precision requirement (<8 ppm for XCO2 and <34 ppb for XCH4) with substantial margins. In addition, FLEXPART model simulations using regional emissi...