Re: GRIB to netCDF

Use

http://www.ncl.ucar.edu/Document/Tools/ncl_convert2nc.shtml

The -itime option forces a time dimension.

%> ncl_convert2nc foo.grb -itime

Note that -itime follows the file name

===========================================

http://www.ncl.ucar.edu/Document/Functions/Built-in/setfileoption.shtml

In your script

setfileoption("grb","SingleElementDimensions","Initial_time")

before any addfile

On 04/09/2012 12:47 PM, Guo Zhang wrote:
> Hi,
> I have 3-hourly grib files and want to extract variables from these files.
> I use the example efficient GRIB to nc:
> http://www.ncl.ucar.edu/Applications/gribeff.shtml. But I cannot figure
> out how to assign time attribute. 'fatal:No valid instance of variable
> initial_time found in file list'.
> Please see my script and data information below. Also can access my some
> data and script via bluefire: /glade/home/zhangg/gld/nc.ncl GLDAS*.grb.
> Thanks.
> -Guo Zhang
>
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> ;************************************************
> undef("rdVar4D")
> function rdVar4D (f:file, vName:string, time:integer)
> ; read GRIB 4D variable and assign new dimension names
> begin
> var = f->$vName$; read variable
> var!0 = "time" ; assign 'conventional' dimension names
> var!1 = "lat"
> var!2 = "lon"
> var&time = time ; assign time coord variable
> return(var)
> end
> begin
> ;***********************************************
> ; read in data from GRIB file
> ;***********************************************
> gribfil = systemfunc("ls *.grb")
> grib_in = addfiles(gribfil, "r")
> ; print(grib_in) ; file overview
> ; print(gribfil(0))
> TIME = grib_in[:]->initial_time ; time as "hours since"
> lat = grib_in[:]->g0_lat_0 ; latitude
> lon = grib_in[:]->g0_lon_1 ; longitude
> lat!0 = "lat" ; assign new dimension name
> lon!0 = "lon"
> TIME!0= "time"
> time = cd_calendar(TIME, -3) ; change to date syntax
> time!0= "time"
> time@units <mailto:time@units> = "yyyymmddhh"
> snowf = rdVar4D (grib_in, "VAR_131_GDS0_SFC" ,time)
> rainf = rdVar4D (grib_in, "VAR_132_GDS0_SFC" ,time)
> ....
> file global attributes:
> dimensions:
> g0_lat_0 = 600
> g0_lon_1 = 1440
> lv_DBLY2 = 4
> variables:
> float PRES_GDS0_SFC ( g0_lat_0, g0_lon_1 )
> center : Zagreb
> long_name : Pressure
> units : Pa
> _FillValue : 1e+20
> level_indicator : 1
> gds_grid_type : 0
> parameter_table_version : 1
> parameter_number : 1
> forecast_time : 0
> forecast_time_units : hours
> initial_time : 01/01/2008 (00:00)
> float TMP_GDS0_SFC ( g0_lat_0, g0_lon_1 )
> center : Zagreb
> long_name : Temperature
> units : K
> _FillValue : 1e+20
> level_indicator : 1
> gds_grid_type : 0
> parameter_table_version : 1
> parameter_number : 11
> forecast_time : 0
> forecast_time_units : hours
> initial_time : 01/01/2008 (00:00)
> float WIND_GDS0_SFC ( g0_lat_0, g0_lon_1 )
> center : Zagreb
> long_name : Wind speed
> units : m/s
> _FillValue : 1e+20
> level_indicator : 1
> gds_grid_type : 0
> parameter_table_version : 1
> parameter_number : 32
> forecast_time : 0
> forecast_time_units : hours
> initial_time : 01/01/2008 (00:00)
> float SPF_H_GDS0_SFC ( g0_lat_0, g0_lon_1 )
> center : Zagreb
> long_name : Specific humidity
> units : kg/kg
> _FillValue : 1e+20
> level_indicator : 1
> gds_grid_type : 0
> parameter_table_version : 1
> parameter_number : 51
> forecast_time : 0
> forecast_time_units : hours
> initial_time : 01/01/2008 (00:00)
> float EVP_GDS0_SFC ( g0_lat_0, g0_lon_1 )
> center : Zagreb
> long_name : Evaporation
> units : kg/m^2
> _FillValue : 1e+20
> level_indicator : 1
> gds_grid_type : 0
> parameter_table_version : 1
> parameter_number : 57
> forecast_time : 0
> forecast_time_units : hours
> initial_time : 01/01/2008 (00:00)
>
>
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Received on Mon Apr 9 13:12:27 2012