Impact

1. Effects of 3D radiative transfer in the Sierra Nevada Mountains • Objective • Investigate the effects of 3D interactions between solar radiation and mountain topography on surface fluxes and land surface processes • Approach • Implement 3D radiative transfer parameterization over mountains in the Weather Research and Forecasting (WRF) model • Apply the model to a western U.S. region focusing on the Sierra Nevada mountains at 30 km resolution for a case study of a relatively clear day in the spring season • Compare simulations with and without the 3D radiative transfer parameterization to account for solar flux deviations from flat surfaces and assess their effects on surface fluxes and land surface processes such as snow and soil moisture Deviations of downward solar fluxes from flat surface simulated in the Sierra Nevada mountains at 9am (left), 12pm (middle), and 3pm (right) • Impact • Mountain topography can induce up to – 50 W/m2 and 50 W/m2 deviations in solar fluxes reaching the surface in the Sierra Nevada mountains with surface temperature increase up to 1oC in the sunny side, leading to reduced snowpack and increased soil moisture (due to snowmelt) • This study motivates the need to assess the climatic effects of 3D radiative transfer in mountains and implications to the hydrological cycle in mountainous regions worldwide Gu Y, KN Liou, W-L Lee, and LR Leung. 2012. “Simulating 3D Radiative Transfer Effects Over the Sierra Nevada Mountains Using WRF.”Atmospheric Chemistry and Physics 12:9965–9976. DOI:10.5194/acp-12-9965-2012