Comparisons of Satellite-Derived Cloud Heights with Radar Measurements of Mid-Level, Mixed-Phase Clouds

摘要

Radiances from the 10.7 micrometers channel of Geostationary Operational Environmental Satellite-8 are converted to cloud top height (CTH) for comparison to 95 GHz radar measurements of mid-level, mixed-phase clouds. CTH is objectively determined by airborne cloud radar and used as ground truth. Three methods of satellite-derived CTH are compared to the radar. The black body (BB) method assumes the cloud radiates as a black body, converts the radiance to brightness temperature and height via comparison to an atmospheric sounding. Errors range from +900 m to -1200 m depending on the opaqueness of the cloud. The spatial coherence (SC) method determines a single mean value of cloud top radiance for a cloud scene and converts the radiance to height in a manner similar to the BB method. Errors range from +200 m to +900 m without much dependence on opaqueness. The optimal estimation method determines CTH using BB radiances and a SC method with an a priori' constraint from a sounding. The solution is determined iteratively using a perturbation method. Errors range from +200 m to +700 m with only a slight dependence on the opaqueness of the cloud until the clouds become very optically thin.