In this study, we have assimilated the AIRS column weighted CO2 retrievals along with all the meteorological observations assimilated in NCAR/DOE Reanalysis 2 in the NCAR carbon-climate model. We discussed a proper way to obtain CO2 vertical profiles based on column-integrated data. An initial test has been carried out to estimate surface carbon flux based on both AIRS CO2 observations and conventional surface CO2 observations within the LETKF data assimilation framework. Surface carbon flux is estimated by appending to the CO2 dynamical vector during data assimilation. It is updated by using the covariance between CO2 concentration and surface carbon flux.
The results show that the accuracy of CO2 vertical profiles have been improved by assimilation of the column weighted AIRS CO2 observations, when compared to independent aircraft CO2 observations. The preliminary surface carbon flux estimation shows that AIRS CO2 observations have more impact on surface carbon flux over tropical region where AIRS CO2 observations is more related to surface carbon flux due to strong vertical mixing.