These images show the joint distributions of cloud top temperature, particle size, and optical depth with relative humidity with respect to ice (RHic), all of which are calculated from AIRS. (A) Normalized frequency distributions of RHic binned into intervals of 10%. (B) Percentage of cases with specific humidity between 15-30 ppmv; instances with specific humidity <15 ppmv not included because of the insensitivity and unreliability of specific humidity in dry conditions. (C) RHic vs. cloud top temperature (K). (D) RHic vs. particle size (microns). These figures show that RHic tends to increase with decreasing cloud top temperature, increasing optical depth, and decreasing particle size. Even though the thin cirrus clouds are usually geometrically thinner than the vertical resolution of AIRS temperature and specific humidity, these results are consistent with those from some in situ campaigns and demonstrate the utility of AIRS to characterize joint distributions of humidity and cloud properties.
Kahn, B. H., Liang, C. K., Eldering, A., Gettelman, A., Yue, Q., and Liou, K. N.: Tropical thin cirrus and
relative humidity observed by the Atmospheric Infrared Sounder, Atmos. Chem. Phys., 8, 1501-1518, 2008.