Solar Irradiance in the WRF-Solar Simulations Using a New Microphysics Parameterization

Although it has been well recognized that clouds tremendously affect the surface solar irradiance and its direct and diffuse partitions, accurately forecasting solar radiation in cloudy conditions remains a major challenge. To improve the simulation of solar irradiance, we need to improve the simulated clouds especially their microphysical properties. In this study, we focus on the effects of cloud microphysics on solar irradiance and the improvements of microphysics parameterization. First, several commonly used microphysics schemes will be tested in different cloud regimes (shallow cumulus v.s. stratocumulus) using the state of art Weather Research and Forecast model designed for solar radiation simulation and forecasting (WRF-Solar). The simulations will be evaluated against the measurements at the DOE ARM SGP site to better understand the physical causes of the resulted solar irradiance in the model. Second, we will introduce a revised microphysics parameterization and investigate the performance of the new scheme. The new scheme will be compared to other microphysical schemes to see the changes in microphysical properties and the impact on solar irradiance. The results will provide physical insight into the improvement of solar irradiance forecast in cloudy conditions.