[Met_help] Input data for point-stat tool
John Halley Gotway
johnhg at rap.ucar.edu
Thu Sep 25 09:14:00 MDT 2008
Valerio,
Sorry, no. I don't have any experience using "cdo". I'll be interested to hear if you're successful using it.
John
capecchi wrote:
> John,
> thanks very much for your help, I decided to convert my NetCDF file to GRIB1
> file
> using `cdo -f grb copy ...` command...do you have any (...) about known
> problems with this
> procedure?
> Anyway I hope version 2.0 of MET will accept general format of NetCDF files.
> Thanks again, bye, Valerio
>
> 2008/9/23 John Halley Gotway <johnhg at rap.ucar.edu>
>
>> Valerio,
>>
>> I do think that it would be reasonable to massage your NetCDF files into a
>> format that METv1.1 would read. However, METv1.1 is only compatible with a
>> rather rigid format of NetCDF at this point. For
>> the next release of MET, version 2.0, we're planning to support a more
>> general format of NetCDF.
>>
>> Currently, MET expects gridded NetCDF data to abide by the following
>> conventions:
>>
>> (1) dimensions named "lat" and "lon" define the dimension of the data.
>> (2) variables have only two dimensions, "lat" and "lon".
>> (3) variables are named using the GRIB code abbreviation for the GRIB field
>> they represent and are in the units prescribed by that GRIB code. For
>> example, a variable containing accumulated
>> precipitation would be named "APCP" (GRIB code abbreviation) and its units
>> would be millimeters.
>> (4) several variable attributes are required to define the initialization,
>> valid, and accumulation (if applicable) times.
>> (5) global attributes defining the grid on which the data resides must be
>> defined.
>>
>> The definition of the grid in (5) is necessary to perform conversions
>> between lat/lon and grid x/y.
>>
>> I've attached a sample output file from PCP-Combine. This example contains
>> data on a lat/lon grid - which I'm guessing is the projection your data is
>> on. The attached file that ends in ".dump" is
>> just a dump of the NetCDF header. In that file, please note the following:
>>
>> (1) The "lat" and "lon" dimensions are defined.
>> (2) The variable named APCP contains accumulated precipitation in mm. The
>> GRIB codes and corresponding abbreviations are defined here:
>> http://www.nco.ncep.noaa.gov/pmb/docs/on388/table2.html
>> (3) The APCP variable contains the several attributes, but only the
>> following are actually read by the code: level, init_time_ut, valid_time_ut,
>> and accum_time (if not applicable, just set to 0).
>> The "_ut" is for unixtime, or seconds since January 1, 1970.
>> (4) Global attributes defining the projectsion:
>> :Projection = "LatLon" ;
>> :lat_ll_deg = "25.063000 degrees_north" ;
>> :lon_ll_deg = "-124.938000 degrees_east" ;
>> :delta_lat_deg = "0.125000 degrees" ;
>> :delta_lon_deg = "0.125000 degrees" ;
>> :Nlat = "224 grid_points" ;
>> :Nlon = "464 grid_points" ;
>> Here you'll just insert your grid definition info.
>>
>> Hope that helps, and feel free to write with more questions about this.
>>
>> John Halley-Gotway
>> johnhg at ucar.edu
>>
>>
>> capecchi wrote:
>>> Dear met_help,
>>> I'm currently involved in WRF verification issues for a biometeorological
>>> service in Italy.
>>> I'm interested in point-stat tools but I have, as input forecast data,
>>> NetCDF files derived and post-elaborated from WRF GRIB1 output.
>>> I read from MET User Guide that I'm supposed to provide as input data
>> only
>>> GRIB1 files or NetCDF format
>>> that is output from the Pcp-Combine tool; I'm wondering if my NetCDF file
>>> format are like the Pcp-Combine tool's format
>>> (I'm attaching one as sample) or if you can suggest me some NetCDF to
>> GRIB1
>>> converter tools (like cdo, nco, or...)
>>> Thanks in advance for any help you can give me, regards, Valerio Capecchi
>>>
>>>
>> **************************************************************************
>>> Valerio Capecchi
>>>
>>>
>> --------------------------------------------------------------------------
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>>> Tel: +39 0553288257
>>> Fax: +39 055332472
>>>
>>> WEB http://www.unifi.it/cib
>>>
>> ---------------------------------------------------------------------------
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>> Modelling)
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>>>
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>> netcdf nam.20070330.ncep110 {
>> dimensions:
>> lat = 224 ;
>> lon = 464 ;
>> variables:
>> float lat(lat, lon) ;
>> lat:units = "degrees_north" ;
>> lat:long_name = "Latitude" ;
>> lat:_FillValue = -9999.f ;
>> float lon(lat, lon) ;
>> lon:units = "degrees_east" ;
>> lon:long_name = "Longitude" ;
>> lon:_FillValue = -9999.f ;
>> float APCP(lat, lon) ;
>> APCP:grib_code = 61 ;
>> APCP:units = "kg/m^2" ;
>> APCP:long_name = "Total precipitation" ;
>> APCP:level = "SFC" ;
>> APCP:_FillValue = -9999.f ;
>> APCP:init_time = "20070330_000000" ;
>> APCP:init_time_ut = 1175212800 ;
>> APCP:valid_time = "20070331_120000" ;
>> APCP:valid_time_ut = 1175342400 ;
>> APCP:accum_time = "6 hours" ;
>>
>> // global attributes:
>> :FileOrigins = "File /home/johnhg/nam.20070330.ncep110.ncgenerated 20080923_163157 UTC on host billiken by the PCP-Combine tool" ;
>> :RunCommand = "Addition:
>> /home/johnhg/nam.20070330.ncep110.grb with accumulation of 3 hours plus
>> /home/johnhg/nam.20070330.ncep110.grb with accumulation of 3 hours." ;
>> :Projection = "LatLon" ;
>> :lat_ll_deg = "25.063000 degrees_north" ;
>> :lon_ll_deg = "-124.938000 degrees_east" ;
>> :delta_lat_deg = "0.125000 degrees" ;
>> :delta_lon_deg = "0.125000 degrees" ;
>> :Nlat = "224 grid_points" ;
>> :Nlon = "464 grid_points" ;
>> }
>>
>>
>
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