Ground-Based Full-Sky Imaging Polarimetric Cloud Detection

Abstract

In many meteorological stations the accurate determination of sky conditions, especially the detection of clouds, is a desirable yet rarely attainable goal. Traditionally, sky conditions are reported by human observers with considerable discrepancies between individual and subjective reports. In practice, employing human observers is not always feasible due to budgetary constraints. Human observers can be replaced by automatic full-sky imager systems, like the Scripps-produced Whole Sky Imager, or the TSI-880 Total Sky Imager produced by the Yankee Environmental Systems, Inc. (YES 2001). These systems provide real-time processing and display of daytime sky conditions using common image processing algorithms, which detect the clouds radiometrically by filtering the colour picture of the sky so that the approximate value of the cloud cover fraction can be calculated.