Solar radiative transfer in a 3D CSRM simulation of a “mock-Walker” circulation

Most, if not all, Cloud System Resolving Models (CSRMs) use the Independent Column Approximation (ICA) for computation of radiative transfer. Many studies have shown that there can be locally large instantaneous biases between radiative fluxes computed using 3D methods and fluxes computed using the ICA, especially for solar wavelengths. What is not clear is if these systematic biases can in turn affect systematic biases within the simulations performed with CSRMs. Analysis of 2D CSRM simulations of a large domain atop an ocean with prescribed sinusodially varying sea surface temperatures suggested that computing solar radiative transfer using 3D or ICA produced very similar results for several diagnostics. This implies that the impact of using the more complicated 3D solar radiative transfer was minimal. To examine if these results are a byproduct of using a 2D CSRM domain, simulations were repeated using a 3D CSRM domain in which the solar radiative transfer was computed using either 3D or ICA radiative transfer. Results from these 3D CSRM simulations will be presented.