Comparison of Cloud Liquid Water Paths Over Atmospheric Radiation Measurement Southern Great Plains Using Satellite and Surface Data: Validation of New Models

Cloud liquid water path (LWP) is a crucial parameter for climate studies, especially for use in general circulation models. To provide a long-term, large-scale dataset of this important parameter, the Visible Infrared Solar Split-Window Technique (VISST) retrieval method is used to derive LWP over the Atmospheric Radiation Measurement (ARM) Climate Research Facility Southern Great Plains (SGP) site. For accurate derivation of LWP, a priori knowledge or assumption of several parameters is required. For the VISST technique, values of the optical depth and effective radius are required to determine LWP. VISST determines optical depth by matching satellite-observed 0.65-μm reflectances to a parameterization of theoretically derived reflectance calculations for seven water droplet size distributions (Minnis et al. 1998). It derives droplet size effective radius in similar manner by matching the observed 3.9-μm reflectance to the parameterized model reflectances. These models are dependent upon an assumed particle size distribution, which is governed by the variance in the water droplet size distribution.