Effect of The Surface Texture Of Ice Particles On The Retrieval Of Cirrus Properties
Abstract
Surface roughness of ice crystals is a morphological parameter important to the scattering characteristics of these particles. The intent of this study is to quantify the effect of surface roughness on the retrieval of the optical and microphysical properties of cirrus clouds from satellite observations. We present two raytracing algorithms, a rigorous algorithm and an approximate algorithm with a simplified treatment of surface roughness, for calculating the singlescattering properties of randomly oriented hexagonal ice crystals with size parameters in the geometric optics regime. It is shown that the simplified scheme can account for most the effects of surface roughness on particle singlescattering properties without incurring substantial demand on computational resources, and thus provides an efficient way to compute the singlescattering properties of roughened particles. The simplified raytracing technique is employed to compute the singlescattering properties of hexagonal columns at wavelengths 0.86 and 2.13 ?m. Lookup tables built for the correlation between the bidirectional reflectances at wavelengths 0.86 and 2.13 ?m with different roughness conditions are used to retrieve ice cloud optical thickness and effective particle size over oceans. In general, the dominant effect of surface roughness on cloud property retrievals is to decrease the retrieved optical thickness and to increase the retrieved effective particle size in comparison with their counterparts in the case of smooth ice particles.
 Publication:

AGU Fall Meeting Abstracts
 Pub Date:
 December 2007
 Bibcode:
 2007AGUFM.A32B..02Y
 Keywords:

 0319 Cloud optics;
 0321 Cloud/radiation interaction;
 0360 Radiation: transmission and scattering