Probability of cloud-free lne of sght (PCFLOS) derived from CloudSat cloud profiling radar (CPR) and coincident CALIPSO lidar data

Numerous global “Cloud-Free Line of Sight” climatologies have been derived from satellite observations of cloud. All have inherent limitations due to the fact that they rely on data from passive meteorological sensors which provide a reasonable measurement of the cloud tops, but provide no information about cloud bases or multi-layered clouds below the highest opaque cloud layer.

NASA's exciting new CloudSat and CALIPSO mission data provide, for the first time from space, a direct measurement of the vertical profile of cloud – including cloud bases and the elusive “hidden layers”.

Four years of CloudSat and CALIPSO data are used to generate Cloud Free Line-of-Sight statistics at 20 vertical levels and 10-degree view angle increments from the satellite perspective. This same technique could be used to generate PCFLOS from a point on the ground along the satellite ground-track.

PCFLOS from these new, active, measurement systems can be used to validate and/or improve existing PCFLOS products from passive space or ground-based observations.