Retrieving profiles of atmospheric CO2 in clear sky and in the presence of thin cloud using spectroscopy from the near and thermal infrared:: A preliminary case study -: art. no. D04316

[1] The benefits and limitations of retrieving a typical source profile of CO2 in the lower atmosphere employing high-resolution measurements from the 1.6 mm region in the near infrared (NIR) and moderate-resolution measurements from the thermal infrared (IR) are explored for clear-sky scenarios as well as scenarios containing thin cloud. With respect to CO2 column-average values, the results of this study show that all errors in CO2 column-average values were 1 ppmv or less for the cases considered. Retrievals using measurements from the NIR alone slightly outperformed those using measurements from the IR alone provided that atmospheric scatterers were properly constrained. It was also found that IR and NIR measurements complement one another in retrieving column CO2 and potentially provide better retrievals than using either set of measurements alone. With respect to CO2 surface values, the preliminary retrieved CO2 profiles show the NIR measurements are the clear winner due to the fact that the NIR obtains its CO2 information from the lower troposphere as opposed to the IR measurements which obtains its CO2 information from the mid and upper troposphere. However, measurements in addition to the NIR measurements ( such as provided by the O-2 A-band or by lidar) would be required to assist in constraining unwanted scattering.