No subject
Wed Apr 14 09:37:02 EDT 2010
isize = 140
jsize = 115
nps (north polar stereographic projection)
ipole (probably can be computed from false_easting; my guess is 3525000/50000 = 70.5)
jpole (probably can be computed from false_northing; my guess is 7525000/50000 = 150.5)
lonref = 263 (-97 might also work)
gridinc = 50000
The nps projection assumes a true latitude of 60N, which is the case for your dataset.
So, in your ctl file, use the following PDEF specification:
pdef 140 115 nps 70.5 150.5 263 50000
For xdef and ydef, they can be arbitrary but the ranges of longitude and latitude (also found in ncdump output) and the resolution can be used for guidance. I would suggest the following:
xdef 293 linear 190 0.5
ydef 131 linear 15 0.5
This will specify the internal GrADS lat-lon grid to cover the region 190E-336E, 15N-80N at 0.5 deg resolution.
My suggested values for ipole and jpole may be wrong, but try them and see what the plot looks like.
Best regards,
Eric L. Altshuler
Assistant Research Scientist
Center for Ocean-Land-Atmosphere Studies
4041 Powder Mill Road, Suite 302
Calverton, MD 20705-3106
USA
E-mail: ela at cola.iges.org
Phone: (301) 902-1257
Fax: (301) 595-9793
----- Original Message -----
From: "Ted Pollock" <edwardp at UALBERTA.CA>
To: GRADSUSR at LIST.CINECA.IT
Sent: Saturday, December 6, 2008 9:17:32 PM GMT -05:00 US/Canada Eastern
Subject: Re: A question about polar stereographic projection
Hi,
Have you tried the FILEHEADER option in your ctl file? You can get
grads to skip past all the NetCDF data description information and
read only the raw data this way.
Unfortunately I couldn't get the yrev option working with the pdef
option for some reason and that might be necessary with polar data. I
would appreciate it if anyone might be able to provide some
information on that.
Good luck with it,
Ted
Quoting "Li,Guilong [Ontario]" <Guilong.Li at EC.GC.CA>:
> Dear Grads users,
>
> I have a netcdf file with polar stereographic projection which can not
> be opened by sdfopen. When I check the user group, I find I have to
> write a control file to overwrite sdf file. After I tried several times
> to write a new control file to open this netcdf file, it doesn't work.
>
> Can someone help me about this question? Thanks a lot.
>
> Guilong
>
> Here is the ncdump -h output.
>
> netcdf pr_MRCC_1979010103 {
> dimensions:
> xc = 140 ;
> yc = 115 ;
> time = UNLIMITED ; // (5848 currently)
> bnds = 2 ;
> variables:
> double yc(yc) ;
> yc:units = "m" ;
> yc:long_name = "y-coordinate of polar_stereographic
> projection" ;
> yc:standard_name = "projection_y_coordinate" ;
> yc:axis = "Y" ;
> yc:coordinate_defines = "point" ;
> yc:actual_range = 0.f, 5700000.f ;
> double xc(xc) ;
> xc:units = "m" ;
> xc:long_name = "x-coordinate of polar_stereographic
> projection" ;
> xc:standard_name = "projection_x_coordinate" ;
> xc:axis = "X" ;
> xc:coordinate_defines = "point" ;
> xc:actual_range = 0.f, 6950000.f ;
> double time(time) ;
> time:long_name = "time" ;
> time:calendar = "gregorian" ;
> time:standard_name = "time" ;
> time:axis = "T" ;
> time:units = "days since 1979-01-01 00:00:0.0" ;
> time:delta_t = "0000-00-00 03:00:00" ;
> time:coordinate_defines = "point" ;
> time:actual_range = 0.125f, 731.f ;
> time:bounds = "time_bnds" ;
> double lon(yc, xc) ;
> lon:units = "degrees_east" ;
> lon:long_name = "longitude" ;
> lon:standard_name = "longitude" ;
> lon:axis = "X" ;
> lon:actual_range = 199.8962f, 326.4349f ;
> double lat(yc, xc) ;
> lat:units = "degrees_north" ;
> lat:long_name = "latitude" ;
> lat:standard_name = "latitude" ;
> lat:axis = "Y" ;
> lat:actual_range = 20.60496f, 73.2522f ;
> char polar_stereographic ;
>
> polar_stereographic:straight_vertical_longitude_from_pole = 263.f ;
> polar_stereographic:standard_parallel = 60.f ;
> polar_stereographic:false_easting = -3525000.f ;
> polar_stereographic:false_northing = -7525000.f ;
> polar_stereographic:latitude_of_projection_origin = 90.f
> ;
> polar_stereographic:grid_mapping_name =
> "polar_stereographic" ;
> polar_stereographic:resolution_at_standard_parallel =
> 50000.f ;
> float pr(time, yc, xc) ;
> pr:units = "kg m-2 s-1" ;
> pr:type = "average" ;
> pr:long_name = "Precipitation" ;
> pr:standard_name = "precipitation_flux" ;
> pr:cell_methods = "time: mean (interval: 3 hours)" ;
> pr:missing_value = 1.e+20f ;
> pr:_FillValue = 1.e+20f ;
> pr:actual_range = 0.f, 0.003506777f ;
> pr:add_offset = 0.f ;
> pr:scale_factor = 1.f ;
> pr:coordinates = "lon lat" ;
> pr:grid_mapping = "polar_stereographic" ;
> pr:level_desc = "Surface" ;
> pr:grid_desc = "polar_stereographic" ;
> double time_bnds(time, bnds) ;
>
> // global attributes:
> :institution = "Ouranos (Ouranos, Montreal, PQ, Canada)"
> ;
> :source =
> "MRCC(2006):atmosphere:MRCCv4.2.0(50km,29levels):sea
> ice:AMIPII:land:CLASSv2.7" ;
> :project_id = "NARCCAP" ;
> :realization = "1" ;
> :experiment_id = "present-day climate using NCEP/DOE
> Reanalysis" ;
> :contact1 = "Sebastien Biner" ;
> :contact2 = "biner.sebastien at ouranos.ca" ;
> :contact3 = "550 Sherbrooke Ouest, 19e etage, Montreal,
> PQ, H3A 1B9, Canada" ;
> :contact4 = "tel : (514)282.6464 poste 263" ;
> :history = "created 24/04/2004 by Ton Nom (netCDF3.6.1
> udunits1.12.4)" ;
> :table_id = "Table 2" ;
> :Conventions = "CF-1.0" ;
> }
>
>
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