Energy Sciences High Energy and Nuclear Physics Advanced Scientific Computing Research and Other Projects Isosurface of cloud water depicting the outer boundary of a trade cumulus cloud in simulations for studying the effects of aerosol pollution on clouds and hence global climate. The technical objective is to build the most advanced explicit aerosol and cloud microphysics model. Computational Approach For the dynamics, we solve the anelastic form of the Navier-Stokes equations in flux form on a rectangular grid using finite difference techniques. The advection algorithm is second-order accurate for smooth flows. For the aerosol and cloud microphysics code, the particle size distributions are resolved on a fixed mass grid with size bins of geometrically increasing width.
Condensational growth is treated using the piecewise polynomial method for advection in mass space.
For the plane-parallel radiative transfer model, particle scattering and absorption coefficients are calculated using Mie theory. Gaseous absorption and emission are treated using an exponential sum formulation. Previously we assumed the sgs mixing length scale was fixed by the model resolution, but we obtained realistic results when the sgs mixing length decreased with increasing atmospheric stability if precipitation was included. In February and March 1999, a dark, murky haze was observed throughout the Indian Ocean, and there were very few clouds. We used our large eddy simulation model to investigate the possibility that solar heating due to the carbonaceous haze evaporated the clouds.