Analysis of cloud optical thickness and effective radius retrievals for broken cloud fields

Radiative transfer model results at two wavelengths (i.e., visible and near IR) can be applied to satellite imagery to infer optical properties of clouds. In this study, the authors examine several types of cloud fields to gain an understanding of the effect of broken cloudiness on cloud property retrievals. Reliable estimates of cloud properties can be obtained for large scale, stratiform cloud fields over water. The same appears to be true even for optically thin (/spl tau/<10), broken cloud fields over water. However, such is not the case for continental fair weather cumulus cloud fields. Three-dimensional cloud effects cause significant disagreement between measured and modelled reflectance. The authors also examine the effects of spatial resolution on cloud property retrievals. When simulating imagery obtained by a low spatial resolution instrument with their high spatial resolution imagery, the 3D cloud effects are filtered out and subsequent retrievals appear reasonable; however, because of the nonlinear relationship between reflectance and optical properties, some bias is likely.<
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