Impacts of aerosol and albedo on TanSat CO2 retrieval using the near infrared CO2 bands

The global carbon dioxide observation satellite (TanSat) mission of China is introduced. Two instruments carried by TanSat including carbon dioxide (CO2) spectrometer with high spectral resolution, termed the TanSat CO2 Spectrometer (TSCS), and the Cloud and Aerosol Polarize Instrument (CAPI) will make global measurements of atmospheric CO2 with the high precision of 1% and resolution of 1 km approximately. In this paper, we aim at quantifying the error associated with aerosol and albedo over China utilizing the new designed parameters of TanSat. Firstly, the latest specifications of TSCS are analyzed through the observing simulations as well as the retrieval experiments over some areas in China, where space-based measurements of CO2 confront the huge challenge induced by atmospheric aerosols which optical depth can ascend up to more than 1 at wavelengths of 550 nm at certain atmospheric conditions. MODIS aerosol and albedo products are used in the synthetic measurements. The impacts of both aerosol scattering and surface albedo on CO2 retrieval accuracy are investigated by applying different retrieval implementation. The errors are estimated for nadir observation over land with typical solar zenith angle 30 degrees and 60 degrees. Comparisons amongst the three approaches suggest that correctly treatment of aerosol scattering is necessary to account for the impacts of multiple scattering in order to meet the requirement of TanSat mission. The development of retrieval algorithm will be continued to the launch of TanSat in late 2015.