The Impact of Cumulus Cloud Field Anisotropy on Broadband Shortwave Radiative Fluxes and Atmospheric Heating Rates

Hinkelman, L.M.(a), Evans, K.F.(b), Clothiaux, E.E.(a), and Ackerman, T.P.(c), The Pennsylvania State University (a), University of Colorado (b), Pacific Northwest National Laboratory (c)
Thirteenth Atmospheric Radiation Measurement (ARM) Science Team Meeting

The effect of fair-weather cumulus cloud field anisotropy on domain average surface fluxes and atmospheric heating profiles has been studied. A stochastice field generation algorithm was used to produce three-dimensional liquid water content fields based on the statistical properties of several cumulus cloud scenes created by a large eddy simulation model. Progressively greater degrees of tilt and stretching were imposed on these scenes, so that an ensemble of scenes were produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. Independent pixel approximation results provide insight into the processes causing these differences.

Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).