Using Windows Version to Read NDFD NetCDF
Jennifer Adams
jma at COLA.IGES.ORG
Mon Nov 14 14:37:44 EST 2005
Ken,
The 'dtype netcdf' option is not available with version 1.8. In order
to read your netcdf file (which has data projected onto a lambert
grid), you will definitely need 1.9b4. Unfortunately, this is not
available for windows.
Jennifer
On Nov 14, 2005, at 1:57 PM, Ken Waters wrote:
> All,
>
> I'm just getting started trying to use GrADS to read netCDF files (the
> NWS National Digital Forecast Database) on a Windows XP box. The data
> set has been converted from GRIB2 to CF-compliant netCDF files using
> the
> NWS MDL "degrib.exe" utililty
> (http://www.nws.noaa.gov/mdl/NDFD_GRIB2Decoder/download.php).
>
> I've successfully installed the latest Windows build that's available,
> Ver. 1.8sl11, native windows version. Someone told me that I can use
> 1.9b4 to read these data, however there are no Windows binaries
> available for that version on the GrADS website. Is the 1.8sl11
> version
> able to read netCDF?
>
> I'm having mixed results finding help in the documentation. For
> example, I found a link labeled "Using GrADS on a PC" (link:
> http://gmao.gsfc.nasa.gov/software/grads/win32/latest/) and it was a
> dead link.
>
> Has anyone had any success viewing netCDF files using the Windows
> version? I did as someone suggested and started with the WRF example
> (http://grads.iges.org/grads/gadoc/wrfvars.ctl) for a control file
> that's found in the documentation. I did an "ncdump -h" of the netCDF
> file ("sky.txt", attached) to get the required header information to
> build the control file and then replaced the information in the WRF
> example to match my data set as best as I could. However, I seem to
> not
> be able to get to step one as I get the following error upon reading
> the
> control file ("sky.ctl", attached):
>
> ga-> open c:\test\sky.ctl
> Scanning description file: c:\test\sky.ctl
> Open Error: Data file type invalid
> --> The invalid description file record is:
> --> dtype netcdf
>
> The data file was not opened.
> ga->
>
> The "dtype netcdf" line is the exact same line that is in the WRF
> example control file online. Does this have something to do with the
> CR/LF problem that someone just posted about? If so, how do I fix it?
>
> As you can tell, I'm really pretty lost and not sure if I can even do
> what I want to do with this version.
>
> Thanks much for any help.
>
> Ken
>
>
> netcdf sky {
> dimensions:
> ProjectionHr = UNLIMITED ; // (174 currently)
> YCells = 252 ;
> XCells = 312 ;
> variables:
> char MapProjection ;
> MapProjection:long_name = "MapProjection" ;
> MapProjection:grid_mapping_name =
> "lambert_conformal_conic" ;
> MapProjection:EarthShape = "sphere" ;
> MapProjection:EarthRadius_KM = 6371.2 ;
> MapProjection:EarthRadius = "6371.200000 km" ;
> MapProjection:standard_parallel = 25. ;
> MapProjection:longitude_of_central_meridian = -95. ;
> MapProjection:latitude_of_projection_origin = 25. ;
> MapProjection:LowerLeftLatitude = 29.26025 ;
> MapProjection:LowerLeftLongitude = -123.12555 ;
> double YCells(YCells) ;
> YCells:units = "m" ;
> YCells:long_name = "y coordinate of projection" ;
> YCells:standard_name = "projection_y_coordinate" ;
> YCells:grid_spacing = "5079.406000 m" ;
> YCells:TrueGridLength_Latitude = 25. ;
> YCells:_CoordinateAxisType = "GeoY" ;
> double XCells(XCells) ;
> XCells:units = "m" ;
> XCells:long_name = "x coordinate of projection" ;
> XCells:standard_name = "projection_x_coordinate" ;
> XCells:grid_spacing = "5079.406000 m" ;
> XCells:TrueGridLength_Latitude = 25. ;
> XCells:_CoordinateAxisType = "GeoX" ;
> float longitude(YCells, XCells) ;
> longitude:long_name = "longitude coordinate" ;
> longitude:units = "degrees_east" ;
> longitude:precision = 6 ;
> longitude:grid_mapping = "MapProjection" ;
> longitude:standard_name = "longitude" ;
> longitude:_CoordinateAxisType = "Lon" ;
> float latitude(YCells, XCells) ;
> latitude:long_name = "latitude coordinate" ;
> latitude:units = "degrees_north" ;
> latitude:precision = 6 ;
> latitude:grid_mapping = "MapProjection" ;
> latitude:standard_name = "latitude" ;
> latitude:_CoordinateAxisType = "Lat" ;
> float Sky_SFC(ProjectionHr, YCells, XCells) ;
> Sky_SFC:long_name = "Total cloud cover" ;
> Sky_SFC:units = "%" ;
> Sky_SFC:coordinates = "longitude latitude" ;
> Sky_SFC:ReferenceTime = 1131642000 ;
> Sky_SFC:ReferenceTimeString = "2005-11-10 17:00:00
> 00:00" ;
> Sky_SFC:gridType = "SCALAR" ;
> Sky_SFC:level = "SFC" ;
> Sky_SFC:DescriptiveLevel = "0[-] SFC=\"Ground or water
> surface\"" ;
> Sky_SFC:OriginatingCenter = 8, 65535 ;
> Sky_SFC:precision = 3 ;
> Sky_SFC:valid_min = 0.f ;
> Sky_SFC:valid_max = 100.f ;
> Sky_SFC:NumMissing = 18260 ;
> Sky_SFC:_FillValue = 9999.f ;
> Sky_SFC:missing_value = 9999.f ;
> Sky_SFC:grid_mapping = "MapProjection" ;
> Sky_SFC:GRIBMessageVersion = 2 ;
> Sky_SFC:GRIBMessageUnits = "%" ;
> Sky_SFC:GRIB2_Discipline = 0 ;
> Sky_SFC:GRIB2_Sect4TemplateNumber = 0 ;
> Sky_SFC:GRIB2_Sect4ParameterCategory = 6 ;
> Sky_SFC:GRIB2_Sect4ParameterNumber = 1 ;
> Sky_SFC:GRIB2_GenerationProcess = 2 ;
> Sky_SFC:GRIB2_FstFixedSurfaceType = 1 ;
> Sky_SFC:GRIB2_FstFixedSurfaceValue = 0. ;
> Sky_SFC:GRIB2_SndFixedSurfaceType = 255 ;
> Sky_SFC:GRIB2_SndFixedSurfaceValue = 0. ;
> short ProjectionHr(ProjectionHr) ;
> ProjectionHr:long_name = "Projection Hour After
> ReferenceTime" ;
> ProjectionHr:units = "hours since 2005-11-10 17:00:00
> 00:00" ;
> ProjectionHr:_CoordinateAxisType = "Time" ;
> ProjectionHr:FirstValidTime = 1131645600 ;
> ProjectionHr:FirstValidTimeString = "2005-11-10
> 18:00:00 00:00" ;
> ProjectionHr:FirstProjectionHR = 1. ;
>
> // global attributes:
> :title = "GRIB Data translated to NetCDF" ;
> :Conventions = "CF-1.0" ;
> :CreatedBy = "degrib" ;
> :comment = "Used degrib with: -NetCDF 3" ;
> :references =
> "http://www.nws.noaa.gov/mdl/NDFD_GRIB2Decoder/" ;
> }
> dset ^sky.nc
> dtype netcdf
> undef -888
> TITLE Sky Cover
> pdef 252 312 lcc 29.26025 -123.12555 1 1 25.0 -95.0 5079.406 5079.406
> xdef 270 linear -129 0.1
> ydef 200 linear 26 0.1
> zdef 25 linear 1 1
> tdef 2 linear 11jun2002 3hr
> vars 1
> SKY=>Sky_SFC 0 t,y,x Sky Cover
> endvars
>
--
Jennifer Miletta Adams
Center for Ocean-Land-Atmosphere Studies (COLA)
4041 Powder Mill Road, Suite 302
Calverton, MD 20705 USA
jma at cola.iges.org
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