A physical subgrid scale information exchange (PSIE) systemfor parameterization schemes in numerical weather prediction models

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Numerical weather prediction models have to solve the basic differential equations in aspatially and temporally discretized form. By introducing a numerical grid, all processes of subgridscales are cut off and have to be parameterized to include their influence on the grid scale averages.These physical parameterizations significantly determine the total behavior of the numerical weather prediction model. Contemporary physical parameterization schemes purvey detailed information of the processes in question, but they only provide a part of this information as an average to the grid scale. Subgrid scale information is usually not directly communicated between the different parameterization schemes. The only way for this communication is via the averaged model variables. This causes an inevitable loss of information due to the grid scale averaging and the restriction to the chosen set of prognostic variables. To characterize and to overcome this loss of information, in the proposed research project we plan to develop a physical subgrid scale information exchange (PSIE) system for the parameterization schemes of a numerical weather prediction model. Information related to subgrid scale processes will be exchanged directly between the parameterizations. It is expected that this treatment yields a distinct improvement of the overall forecast quality of the weather prediction model. Since the choice of the prognostic variables and the physical parameterizations depend on the hosting weather prediction model model, we will use two different hosting models for comparison: the COSMO model of the German Meteorological Service and the WRF model developed by the National Center for Atmospheric Research and the National Oceanic and Atmospheric Administration, USA.