A Fast All-Sky Radiative Transfer Model for Solar Applications
Radiative transfer models simulating broadband solar radiation, e.g. Rapid Radiation Transfer Model (RRTM) and its GCM applications, have been widely used by atmospheric scientists to model solar resource for various energy applications such as operational forecasting. Due to the complexity of solving the radiative transfer equation, the radiative transfer computation under cloudy conditions can be extremely time consuming though many approximations, e.g. two-stream approach and delta-M trancation scheme, have been utilized. Thus, a more efficient radiative transfer model is crucial to provide model developers a new option of approximating solar radiation at the land surface with minimal loss of accuracy. In this study, we developed a fast radiative transfer model using the simulated direct normal irradiance (DNI) and diffuse horizontal irradiance (DHI) for cloudy conditions from RRTM with a 16-stream Discrete Ordinates Radiative Transfer (DISORT). This fast radiative transfer model is much more efficient than those utilized by the current GCMs or NWP models since it does not explicitly solve the radiative transfer equation for each individual cloud condition.