WRF - Developmental Testbed Center

that if no description is given for a field, then ungrib will not write that field out to theintermediate files.The final group of fields, which provide GRIB2-specific information, are found under thecolumn headings below.|GRIB2|GRIB2|GRIB2|GRIB2||Discp|Catgy|Param|Level|+-----------------------+The GRIB2 fields are only needed in a Vtable that is to be used for GRIB Edition 2 datasets, although having these fields in a Vtable does not prevent that Vtable from also beingused for GRIB Edition 1 data. For example, the Vtable.GFS file contains GRIB2 Vtablefields, but is used for both 1-degree (GRIB1) GFS and 0.5-degree (GRIB2) GFS datasets. Since Vtables are provided for most known GRIB Edition 2 data sets, thecorresponding Vtable fields are not described here at present.Writing Static Data to the Geogrid Binary FormatThe static geographical data sets that are interpolated by the geogrid program are storedas regular 2-d and 3-d arrays written in a simple binary raster format. Users with a newsource for a given static field can ingest their data with WPS by writing the data set intothis binary format. The geogrid format is capable of supporting single-level and multilevelcontinuous fields, categorical fields represented as dominant categories, andcategorical fields given as fractional fields for each category. The most simple of thesefield types in terms of representation in the binary format is a categorical field given as adominant category at each source grid point, an example of which is the 30-second USGSland use data set.For a categorical field given as dominant categories, the data must first be stored in aregular 2-d array of integers, with each integer giving the dominant category at theWRF-NMM V3: User’s Guide 3-28