Coupled FVGCM-GCE MMF

The Goddard Multi-scale Modeling Framework (MMF) is based on the coupling of the two-dimensional Goddard Cumulus Ensemble Model (GCE) and the finite-volume GCM (fvGCM). The MMF, which replaces cloud parameterizations with a cloud resolving model (CRM), is a very promising approach in climate modeling.  It provides a way to couple low-resolution and high-resolution model physics in an unified framework.  The embedded CRMs can explicitly simulate cloud dynamical and physical processes and provide cloud properties and statistics that match the scale of high-resolution satellite observations.  The use of a GCM will allow the large-scale atmosphere's response to cloud, radiation and surface processes and the evaluation of assumptions used in convectional parameterizations to be studied. The MMF system will improve our understanding of cloud and precipitation processes over many scales of motion ranging from cloud microphysical processes up to large-scale circulations that organize the growth and decay of precipitation systems.  The Goddard MMF includes the fvGCM run at 2.50 x 20 horizontal resolution with 32 vertical layers from the surface to 0.4 hPa and a 2D (x-z) GCE embedded at each fvGCM column using 64 x 28 grid points with 4 km horizontal resolution and a cyclic lateral boundary. Globally, there are a total of 13,104 GCEs running at the same time. The time step for the 2D GCE is 10 seconds, and the fvGCM-GCE coupling frequency is one hour (i.e. the fvGCM physical time step). At each fvGCM column, the global model provides the mean atmospheric conditions and the large-scale temperature and moisture advection forcings to the GCE and the cloud model feedbacks the tendencies of thermodynamic variables and cloud statistics.  in each grid column of a GCM.

The finite volume GCM (fvGCM) has been constructed with the unique finite-volume dynamic core developed at Goddard (Lin 2004) and the physics package from the NCAR Community Climate Model CCM3 (Kiehl et al. 1998).  The unique features of the finite-volume dynamical core include: an accurate conservative flux-form semi-Lagrangian transport algorithm (FFSL) with a monotonicity constraint on sub-grid distribution that is free of Gibbs oscillation (Lin and Rood 1996, 1997), a terrain-following Lagrangian control-volume vertical coordinate, a physically consistent integration of pressure gradient force for a terrain-following coordinate (Lin 1997, 1998), and a mass, momentum, and total energy conserving mapping algorithm for Lagrangian to Eulerian control-volume vertical coordinate transformation.  The physical parameterizations in the fvGCM have been upgraded with the gravity wave scheme from the NCAR Whole Atmosphere Community Model (WACCM) and the CLM version 2 (CLM-2).  The fvGCM also includes the ability to use passive water vapor tracers to diagnose the geographic source of water in precipitation and to provide quantitative diagnostics of precipitation recycling (Bosilovich and Schubert 2002).