Diurnal variations of the water cycle in the Goddard Multi-scale Modeling Framework

The foremost challenge in parameterizing cloud systems in general circulation models (GCMs) are many coupled processes that interact over a wide range of scales, from microphysical to planetary scale. This makes the comprehension and representation of cloud systems one of the most complex scientific problems in earth system modeling. Recently, the Multi-scale Modeling Framework (MMF) [or a super-parameterization], which replaces the conventional parameterizations with a cloud resolving model (CRM) in each grid column of a GCM, is a new and promising approach to break the deadlock of conventional cloud parameterizations. The MMF can provide global coverage as well as the dynamical and physical interactions over a wide range of scales. The Goddard MMF has been successfully developed based on a 2D version of the Goddard Cumulus Ensemble (GCE) model and the Goddard finite volume GCM (fvGCM). We have analyzed the Goddard MMF model outputs from two yearly MMF control experiments and compared them with the model outputs from fvGCM AMIP runs, the analysis, and satellite observations to evaluate the performance of the MMF. One of the important validations is the ability of the model to simulate the observed climatology of diurnal variations of cloudiness and precipitation over the ocean and land. High-resolution cloud and precipitation observations from multiple satellites have been used for this comparison. The preliminary results show that in general the MMF is superior to the fvGCM in the frequency and diurnal variability of precipitation and cloud. Some sensitivity experiments are also carried out to understand the impacts of physical processes and MMF setups on the diurnal variability of precipitation. The main objective of this study is to understand the diurnal behavior in atmospheric water cycle and improve the convectional parameterizations in GCMs.