HDF to netcdf: TRMM satellite data for use with MET verification software

Hi.
Could I have a suggestion for creating ³init_time, init_time_ut, valid_time,
valid_time_ut, accum_time,² as variable attributes? I am confused as to
which of NCLS¹s ³Date Routines² to use.

I pretty much understand everything else about creating the netcdf
file-variable, but not assigning time attributes as date commands (email
below is meant for context).

WHAT AM I DOING: I Œm converting TRMM HDF data to netcdf. I have to assign
specific attributes so that a NCAR verification software package (MET)
expects. MET expects users to have precip data in GRIB record format.
WHY: TRMM is not available in GRIB.

Thank you for the help.
Erik

To put into context
Erik,

Listed below is a NetCDF header dump of one of the output files from the
METv1.1 test script for pcp_combine.

Regarding (2), I'd suggest adding the same type of variable attributes that
are listed here:
- grib_code = 61
- units = "kg/m^2" or "mm"
- level = "SFC"
- _FillValue = -9999.f
- init_time = "20050807_000000"
- init_time_ut = 1123372800
- valid_time = "20050808_000000"
- valid_time_ut = 1123459200
- accum_time = "24 hours"

The "_ut" times listed above are in unixtime - the number of seconds that
have elapsed since Jan 1, 1970. A fancy "date" command can be used to give
you the unixtime.
For example, the unixtime corresponding to 8am on July 29, 2008 is given by
the following command: date -ud '2008-07-29 UTC 08:00:00' +%s

Regarding (3), please the following global attributes define the grid on
which this data resides:
- Projection = "Lambert Conformal" ;
- p1_deg = "25.000000 degrees_north" ;
- p2_deg = "25.000000 degrees_north" ;
- p0_deg = "12.190000 degrees_north" ;
- l0_deg = "-133.459000 degrees_east" ;
- lcen_deg = "-95.000000 degrees_east" ;
- d_km = "40.635000 km" ;
- r_km = "6367.470000 km" ;
- nx = "185 grid_points" ;
- ny = "129 grid_points" ;

This example is for a lat/lon grid. You could also use lambert conformal or
polar stereographic. If you have a sample GRIB file already on the grid
you're using, please send it to me, and I can help
you figure out how to specify it in the NetCDF file.

Hope that helps,
John

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Received on Wed Jul 30 2008 - 11:38:54 MDT