“…[] with a nadir footprint of 90 by 90 km 2 [ Chahine et al ., ]. AIRS CO 2 observations have been used to study temporal [e.g., Jiang et al ., ; Li et al ., ] and spatial [e.g., Ruzmaikin et al ., ; Bai et al ., ] variability in midtropospheric CO 2 , to evaluate atmospheric CO 2 simulations [e.g., Feng et al ., ], and for data assimilation studies [e.g., Liu et al ., ; Engelen et al ., ].…”