McIDAS-V can read Gridded Binary (GRIB) files in both GRIB-1 and GRIB-2 formats. Decoding GRIB files requires a set of lookup tables for parameters, issuing centers, etc. McIDAS-V comes pre-configured to support commonly used tables, but regional models and modeling centers may use tables that are not in the distribution.
You can add in specialized tables for both GRIB-1 and GRIB-2 using the steps below. Documentation on the format of the files can be found here.
To add in new GRIB 1 tables, you will need to create a file listing the special tables and the special table files themselves.
To add in a new parameter file, McIDAS-V would need to have access to a file called grib1lookuptable.lst which would list the parameter table (e.g.: gwctab_2.tab) and the parameter table itself.
The format of grib1lookuptable.lst is:
<center>:<subcenter>:<version>: <table location>
so it would look like:
57: 1: 2: gwctab_2.tab
gwctab_2.tab can be a relative or absolute path. The tables are in ncep format:
-1:57:-1:2 0:var0:undefined 1:PRES:Pressure [Pa] 2:PRMSL:Pressure reduced to MSL [Pa] 3:PTEND:Pressure tendency [Pa/s] 4:PVORT:Pot. vorticity [km^2/kg/s] 5:ICAHT:ICAO Standard Atmosphere Reference Height [m] :GP:Geopotential [m^2/s^2] ...
(You can read more information about the format of this file and the parameter table here)
Once you've created this file, you would access it by putting the grib1lookuptable.lst in your <home>/McIDAS-V directory and put the corresponding table files where they are pointed to in the file. This can be a relative path or a web server. Alternatively, you could place the grib1lookuptable.lst and associated parameter tables on a local web server and use McIDAS-V's sitepath parameter (startup option or user preference) to point to the location where the files are.
To add in new GRIB 2 parameter, you would create a file named grib2lookuptable.lst which lists the parameters.
The format of grib2lookuptable.lst is:
<Discipline> <Category> <Parm #> <Name> <Units> <Desc>
Parameters are listed by row, fields are separated by tabs, so it would look like:
#Dis Cat Parm # Name Units Desc 0 0 0 Temperature K Temperature
(This is a sample table, the lines starting with # are not include in table.) (You can read more information about the format of this file and the parameter table here)
Once you've created this file, you would access it by putting the grib2lookuptable.lst in your <home>/McIDAS-V directory. Alternatively, you could place the grib2lookuptable.lst on a local web server and use McIDAS-V's sitepath parameter (startup option or user preference) to point to the location of the file.