Multiyear statistics and parameterization of 2-D shortwave radiative effects at three ARM Climate Research Facility sites

This study examines the importance of horizontal photon transport effects, which are not considered in the 1-D radiation calculations used by most atmospheric dynamical models. In particular, the presentation analyzes the difference between 2-D and 1-D radiative calculations for 2-D vertical cross-sections of clouds that were observed at three sites over 2- to 3-year periods. The results show that horizontal photon transport enhances solar heating at the surface and, to a lesser degree, in the atmosphere. In addition to showing histograms and mean values (ranging to several W/m2 for multiyear, 24-hour averages) for a tropical, mid-latitude, and arctic site operated by the Department of Energy, the presentation also shows that 2-D effects are stronger for high sun and for convective clouds. The results underline the need for fast radiation calculation methods that can allow atmospheric dynamical models to consider the inherently multidimensional nature of shortwave radiative processes. The presentation concludes by showing initial results from our work toward developing a neural-net-based parameterization for this purpose.