In order to validate the performance of the AIRS zonal cloud frequency and amount, we compare the zonal cloud frequency from CloudSat and CALIPSO (two left panels). Then, we derive the frequency of cloud top height from these diagrams, which are shown on the right. Cloud top height is much more comparable to the cloud retrievals from AIRS, since it does not retrieve a true vertical profile. On the bottom panel, the sum of AIRS cloud fraction in both cloud layers is shown. Note that AIRS agrees much more closely with the cloud top climatology observed by the active instruments, although high clouds are somewhat biased low, whereas low clouds are biased a bit high. Also, the relative frequency of occurrence is similar, but the frequency of high clouds is under-detected by AIRS and for low clouds is over-detected.
Citation: Kahn, B. H., Chahine, M. T., Stephens, G. L., Mace, G. G., Marchand, R. T., Wang, Z., Barnet, C. D., Eldering, A., Holz, R. E., Kuehn, R. E., and Vane, D. G.: Cloud type comparisons of AIRS, CloudSat, and CALIPSO cloud height and amount, Atmos. Chem. Phys., 8, 1231-1248, 2008.