P 6 . 11 Cloud Detection Using Measured and Modeled State Parameters

Cloud parameterizations require basic knowledge of the relationships between measured and modeled meteorological state parameters and the cloud properties in a given volume of air. The uncertainty in the relationships, which is especially large for cirrus clouds, is exacerbated by the differences between actual soundings and those produced by various models. Routine surface cloud observations view only the lowermost cloud layers in a column while satellites see only the uppermost cloud layer. With the availability of high temporal resolution Active Remotely Sensed Cloud Location (ARSCL, Clothiaux et al. 2001), radiosondes, and satellite retrievals of cloud properties over the ARM (Atmospheric Radiation Measurement) Southern Great Plains central facility (SCF) site, it is possible to better quantify the relationship between meteorological state parameters and the cloud properties in a given volume of air. This study examines the relationships and differences between modeled and ARM-measured meteorological state parameters in clear and cloudy conditions and develops a temperature-dependent relative-humidity dependent cloud detection method. The resulting empirical models can be used to estimate the probability of cloud occurrence within a given atmospheric layer.