Observations and Stochastic Modeling of Shortwave Radiative Transfer at the ARM CART Sites

Preliminary single-column model (SCM) studies have indicated that the SCM often predicts clear sky conditions when low-level scattered cloudiness actually occurs. Stochastic modeling is a promising technique for representing shortwave radiative transfer through broken cloud fields. Results from the stochastic model may be used to impove the performance of the SCM. To this end, one year of continuously sampled data from the Atmospheric Radiation Measurement (ARM) Programs Clouds and Radiative Testbed (CART) sites (Southern Great Plains, Tropical Western Pacific and North Slopes of Alaska) have been analyzed for input to the stochastic radiative transfer model. The cloud optical and geometric properties were determined using the techniques detailed in Lane, Goris and Somerville (2002). The resulting climatology for all three sites, including cloud height, thickness, fraction and optical properties, will be discussed and results will be compared to similar studies where appropriate (e.g. Lazarus et al. 2000). The output domain-averaged, shortwave radiation fields from the stochastic model will be evaluated using both observations and parallel plane model results to determine appropriateness of this technique as a correction to current shortwave cloud and radiation parameterizations.