PHYSICS-BASED VISUALIZATION OF DENSE NATURAL CLOUDS - I - 3-DIMENSIONAL DISCRETE ORDINATES RADIATIVE-TRANSFER

A technique is developed to model radiative transfer in three-dimensio nal natural clouds with a standard discrete ordinates finite-element m ethod modified to evaluate cell-surface-averaged radiances. A log-leas t-squares-based scale transformation is used to improve the discrete p hase-function model. We handle dense media by assuming constant diffus e radiances over input faces to cubic cells, allowing analytical forms for transmittance factors. Transmission equations are combined with d iffuse volumetric single-scattering calculations to support evaluation s of cell energy balance. Energy not accounted for volumetrically is t reated with surface-based effects. Results produced show accurate flux computations at over 30 optical depths per modeled cell. Comparisons with nonuniform cloud Monte Carlo calculations show less than 1% rms e rror and correlations greater than 0.999 for cases in which cloud-dens ity fluctuations are resolved. OCIS codes: 010.1300, 010.1310, 010.132 0, 010.1110, 290.1090.