P4.35
Cloud overlapping detection algorithm using solar and IR wavelengths
Kazuaki Kawamoto, NASA/LRC, Hampton, VA; and P. Minnis and W. L. Smith
Cloud overlapping seems to be a frequently occurring phenomenon as surface-based radar shows. Since most of the satellite remote sensing techniques of clouds assume a 1-layer cloud system for the retrieval, to detect overlapping cloud cases accurately is very important for improving the quality of the products. It is, however, quite difficult to detect it from space-borne passive radiometer. Though several algorithms such as ones which use infrared (3.7, 11 and 12 um, and 15 um CO2 bands) and near-infrared and infrared (1.6 and 11um) have been developed so far, here we like to propose following two methods using visible (0.64um), solar-infrared(3.7um), infrared (11um)
and split-window (12um) wavelengths. The first one is as follows. Basic idea is that as for enough large cloud optical depth (tau), if the cloud is a single layer, the brightness temperature difference between 11 and 12(um) (hereater BTD45) should be small (nearly equal 0) becase the emissivity
approaches unity, On the other hand, there must be thin cloud over lower cloud, if BTD45 is large. So we can use BTD45 as an indicator to detect
overlap clouds when the total tau is large. The second method makes use
of a potential of particle size tendency for detecting overlapping clouds. VIST (Visible, Solar infrared and Infrared Technique) technique retrieves tau, effective particle radius and cloud temperature with assuming 1-layer cloud. If the cloud system is multilayer, the particle size may show different habit from the one of single case. Motivated by this idea, we compared the effective particle size as a function of the retrieved tau for single and multilayered cases which were determined by 35 GHz cloud radar. Preliminary analysis shows there is distinct separation between single and multilayer cases.
Poster Session 4, Radiances, Clouds, and Retrievals
Wednesday, 17 October 2001, 9:15 AM-11:00 AM
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