Remote sensing through cirrus clouds: visual and sub-visual

Cirrus clouds are composed of ice crystals in various forms. They are known to be widespread (>50% global coverage) and are often transmissive. Intervening cirrus can effect remote sensing retrievals by masking or modulating terrestrial features of interest, and also by introducing additional radiance structure. If detected, these effects may be mitigated or at least acknowledged undetected, they may corrupt the retrieval and inject a systematic bias in the result. In reviewing the effects of cirrus on remote sensing retrievals, the authors discuss: i) Global, seasonal, and synoptic cirrus coverage and cirrus microphysics. ii) Retrieved brightness temperature errors in the infrared as a function of particle properties, cloud optical depth, temperature, etc., as predicted by MODTRAN. iii) VIS and IR appearance of cirrus over terrain, thin cirrus detection. iv) Specular scattering from oriented cirrus particles