One of the most important roles clouds play in the atmosphere is in redistributing radiative energy from the sun and that is emitted from the Earth and atmosphere. However, radiative transfer in the atmospheric sciences is generally modeled crudely because of the perceived computational expense. A 3D Monte Carlo Radiative Transfer model has been developed for massively parallel use on Blue Waters to quantify the relative importance of radiative heating and cooling in various atmospheric scenarios at higher accuracy than ever before. Such a highly accurate model has the capability to provide to the community high spatial resolution radiative quantities such as volumetric heating rates, boundary fluxes, and top of atmosphere radiances that can act as standards of comparison for the less accurate but less expensive radiative transfer models more commonly employed. Challenges in development have included finding the right balance between dynamic load management and communication latency to achieve good scaling.
