Rainfall is a fundamental process within the Earth's hydrological cycle because it represents a principal forcing term in the surface water budget, while its energetics corollary, latent heating, is the principal source of atmospheric diabatic heating in the Tropics to well into middle latitudes. Latent heat production is a consequence of phase changes between the vapor, liquid, and frozen states of water. The vertical distribution of latent heat release modulates large-scale meridional and zonal circulations within the Tropics -- as well as the energetic efficiencies of mid-latitude weather systems.
We propose to use three different modeling systems to advance crucial aspects of TRMM and GPM. The modeling systems are: (1) an improved Goddard Cumulus Ensemble (GCE) model, (2) a coupled global circulation-GCE modeling system (termed a multi-scale modeling framework or MMF), and (3) an advanced regional-scale model (Weather Research Forecast, WRF). These three modeling systems are all coupled with the land information system (LIS) and include the same microphysical processes. This proposed modeling effort will attempt to improve our understanding of cloud and precipitation processes over many scales of motion, ranging from cloud microphysical processes up to the large-scale circulations that organize the growth and decay of precipitation systems. The use of TRMM products and TRMM and other major field campaigns (including GPM GV sites) as a data source for validation and/or assimilation into the models is vital for the success of the NASA Precipitation Missions. The main areas of the proposed research are:
- Provide consistent and comprehensive 4D cloud datasets from the improved GCE model (with improved bulk and spectral-bin microphysics) to TRMM and GPM rainfall retrieval algorithm developers. These cloud datasets include GCE, WRF and MMF-model-simulated clouds and cloud systems from different geographic locations in the Tropics and midlatitudes, winter storms, shallow convection/stratocumulus and those observed at GPM GV sites. Several large-scale re-analyses will also be used to provide large-scale advective forcing to simulate clouds and cloud systems for specific regions that are un-represented in the cloud database.
- Assess and improve the performance of various latent and diabatic heating algorithms. Assist in the improvement of current algorithms by providing 4D cloud datasets from our improved GCE model to heating algorithm developers. Develop a method to retrieve the vertical structure of apparent moistening that is consistent with the retrieved diabatic heating.
- Assess and improve the cloud model microphysics by linking a radiative transfer model to the GCE model. Test retrieval algorithms utilizing high-frequency radiometer channels to improve snow retrievals over land and ocean. Utilize satellite data and field campaigns (i.e., GV) to validate and improve the ""cloud microphysics"" used in GCE and WRF.
- Use global analyses for first-guess fields and boundary conditions for WRF simulations to evaluate the impact of TMI rainfall data on regional-scale hydrological cycles and on significant weather events.
