GCPEx: Cloud Resolving Model (CRM) Simulations
To augment the observations and provide additional test cases for synthetic algorithm development and satellite simulator testing, a number of modeling activities are also planned. Cloud resolving model simulate frozen precipitation events using the GSFC-Weather Research and Forecasting (WRF) will be performed, initialized and forced by appropriate NWP forecast models. The GSFC WRF has single-moment Goddard Microphysics and spectral-bin microphysics. All of the microphysical schemes have their own set of unique capabilities and assumptions, and all will be tested by the GPM groups. In turn, the simulations will be critically constrained by the ground- and aircraft-based in-situ measurements of PSD and density, by aircraft active and passive observations, as well as C-band reflectivities and polarization measurements. This modeling activity will proceed as it did for C3VP and LPVEx, but will be expanded via the enhanced observational capabilities afforded by the instruments provided during GCPEx.
Analysis of these model runs will also provide a CRM-based satellite algorithm testbed for evaluating snowfall retrieval algorithm sensitivities. Application of simulators for all relevant satellite precipitation sensors to output from these simulations will then allow a database of snow scenes to be constructed. Since such scenes are generally lacking in current PMW rainfall retrieval algorithms that tend to be tropics-centric, these simulations will provide a valuable tool for tailoring current retrievals for application at higher latitudes. Advantages of CRM databases include: a) provision of a seamless high-resolution 3D volume; b) vertical and horizontal resolution can be adjusted on request. Disadvantages include a) CRM simulations will have forecast errors to some degree; and b) CRM databases will be biased to some degree even after calibrating assumptions (which are also not perfect in any empirical database) are applied to the CRM microphysics.
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