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The information about climatologically constant data from the external data set is one source of information needed to create forcing data for COSMO-CLM. EXTPAR (External Parameter for Numerical Weather Prediction and Climate Application) is the main program for preparing the external data set. The interactive web frontend WebPEP@DKRZ and WebPEP 🔑 (Web interface for Preprocessing External data Parameters) is available for the generation of the external parameter files with EXTPAR.
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The following steps must be performed for the generation of external parameters:
The target grid has to be specified. Supported target grids are:
Rotated and non-rotated longitude-latitude grid (COSMO)
Icosahedral Triangular grids (ICON) with optionally higher resolution in selected regions (nesting)
The different raw data sets are aggregated to the target grid considering all raw data elements which are located within the target grid element. If the target grid has a higher resolution than the input grid on which the raw data is available, either an interpolation is performed or the target grid is filled with the nearest neighbor, but sub-grid scale statistical calculations (e.g. subgrid scale variance of orographic height) are dismissed in this case.
All the different external parameter sets have to be checked for consistency against each other. In case of conflicts default values are set automatically. In the NetCDF output, information on the input data and the processing software is given.
Latest Version: Extpar 5.0.0 (November 2018)
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