GradsDODS

[Steven Weiss]

Hi Arlindo,

I downloaded the latest lats4d.gs and am getting errors. See reults below.

Regards
Steven

1ga-> lats4d -i http://nomad5.ncep.noaa.gov:9090/dods/waves/nww3/nww320080206/n3_18z -o test -vars htsgwsfs -lat -35 -30 -lon 17.5 30 -v -format grads_grib
lats4d: Version 1.7 of 10 May 2006
No hardcopy metafile open
All files closed; all defined objects released
All GrADS attributes have been reinitialized
Scanning self-describing file:  http://nomad5.ncep.noaa.gov:9090/dods/waves/nww3/nww320080206/nww3_18z
Found 11 data variables in SDF file.
Found displayable variable dirpwsfc with 0 levels in SDF file.
Found displayable variable dirswsfc with 0 levels in SDF file.
Found displayable variable htsgwsfc with 0 levels in SDF file.
Found displayable variable perpwsfc with 0 levels in SDF file.
Found displayable variable perswsfc with 0 levels in SDF file.
Found displayable variable ugrdsfc with 0 levels in SDF file.
Found displayable variable vgrdsfc with 0 levels in SDF file.
Found displayable variable wdirsfc with 0 levels in SDF file.
Found displayable variable windsfc with 0 levels in SDF file.
Found displayable variable wvdirsfc with 0 levels in SDF file.
Found displayable variable wvpersfc with 0 levels in SDF file.
lats4d: Data file is 
File 1 : WAVE_nww3 Global wave model fcst from 18Z06feb2008, downloaded Feb 06 23:11 UTC
  Descriptor: http://nomad5.ncep.noaa.gov:9090/dods/waves/nww3/nww320080206/nww3_18z
  Binary: http://nomad5.ncep.noaa.gov:9090/dods/waves/nww3/nww320080206/nww3_18z
  Type = Gridded
  Xsize = 288  Ysize = 157  Zsize = 1  Tsize = 61
  Number of Variables = 11
    dirpwsfc 0 -999 ** surface primary wave direction [deg] 
    dirswsfc 0 -999 ** surface secondary wave direction [deg] 
    htsgwsfc 0 -999 ** surface sig height of wind waves and swell [m] 
    perpwsfc 0 -999 ** surface primary wave mean period [s] 
    perswsfc 0 -999 ** surface secondary wave mean period [s] 
    ugrdsfc 0 -999 ** surface u wind [m/s] 
    vgrdsfc 0 -999 ** surface v wind [m/s] 
    wdirsfc 0 -999 ** surface wind direction [deg] 
    windsfc 0 -999 ** surface wind speed [m/s] 
    wvdirsfc 0 -999 ** surface direction of wind waves [deg] 
    wvpersfc 0 -999 ** surface mean period of wind waves [s] 

lats4d: Dimension environment file same as data file
lats4d: creating LATS PARAMETER TABLE file .grads.lats.table
LATS warning (lats_parmtab): Closing the previously opened Parameter Table: .grads.lats.table
lats4d: time range: 18Z06FEB2008 18Z06FEB2008 by 1, delta t: 3 hourly
lats4d: vertical levels:  0
lats4d: invalid plev 0 for GRIB output
lats4d: using HYBRID level number for vertical coordinate
lats4d: latitudinal  range: -35 -30
lats4d: longitudinal range: 17.5 30
Failure reading SDF data.  #1
Data Request Error:  Error for variable 'dirpwsfc'
  Error ocurred at column 1
DISPLAY error:  Invalid expression 
  Expression = dirpwsfc
lats4d: error creating grads_grib file test.grb
Original Message ----- 
  From: Arlindo da Silva 
  To: GRADSUSR at LIST.CINECA.IT 
  Sent: Friday, February 08, 2008 3:56 PM
  Subject: Re: GradsDODS


  On Feb 8, 2008 1:44 AM, Steven Weiss <sweiss at iafrica.com> wrote:

    Hi,
    I am downloading a grib file and processing it through my script. It all works great. I have since discovered that I can avoid the 34mb download by using gradsdods and opening up a server url e.g. http://nomad5.ncep.noaa.gov:9090/dods/waves/nww3/nww320080206/nww3_18z

    I can run my script over this successfully however it is painfully slow. I am retrieving all the variables over 180hr for a specified lat/lon grid point.


  Grib2 has great compression capabilities at the expense of speed: it takes time to decompress the files. While switching to GRIB2 may have decresead data storage requirementments for the data producers and download time for the people getting the actual files, it certainly caused a degradation of the OPeNDAP services for sites serving the grib-2 files directly.


    A little bit of investigation tells me that I should be downloading a subset of the data to my local drive i.e. a lat/lon range and running my script over that instead.

    How can I do this? Some examples would be useful.


  If you want to do this over OPeNDAP you can use lats4d (see recent posting for the latest script). Here is an example for creating a subset of the data:

  lats4d -i http://nomad5.ncep.noaa.gov:9090/dods/waves/nww3/nww320080206/nww3_18z  -o myfile -vars ugrdsfc vgrdsfc -lat 20 60 -lon -100 20 -v

  If you omit -vars, you get all variables, if you omit the -lat/-lon you get the whole domain; you can also specify -time/-levs if you would like to subset along those dimensions.  In grads v1.9, by default this will produce a netcdf file called myfile.nc; use "-format grads_grib" to get a grib-1 file, "-format stream" to get a flat binary, "-format sequential" for a f77 sequential file. At this point you can only specify -format sream/sequential with grads v2.

  Another point, you can use this command inside gradsdods, or from the unix command line with the lats4d sh(1) script (this also be done under windows if using sh.exe or tcsh.exe). The command line wrapper is useful for putting lats4d based fetches on a crontab.

         Arlindo









    Regards
    Steven 



  -- 
  Arlindo da Silva
  dasilva at alum.mit.edu
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