Seasonal and Interannual Variability of Mid-tropospheric CO2 from Atmospheric Infrared Sounder

The Atmospheric Infrared Sounder (AIRS) offers an opportunity to investigate the variability of middle tropospheric CO2 over the entire globe [Chahine et al. 2005; 2008]. In this paper, we use AIRS data to examine the annual and interannual variability of CO2 and show that the annual cycle of AIRS CO2 agrees well with Matsueda aircraft measurements over the tropics. We also find significant correlations between AIRS middle tropospheric CO2 concentrations and large-scale atmospheric dynamics. During El Niño events, middle tropospheric CO2 over the central Pacific Ocean is enhanced whereas it is reduced over the western Pacific Ocean as a result of changes in the Walker Circulation. The variation of AIRS CO2 in the high latitudes of northern hemisphere is closely related to the strength of the polar vortex, which can be explained by the large-scale dynamics near the polar region.