[gradsusr] Stage IV HRAP Radar data

[Wayne Gibson]

Hello,

I've been trying unsuccessfully to read a netcdf Stage IV Radar file as 
found in the tar file

      
http://water.weather.gov/p_download_new/2008/200811/nws_precip_20081101_nc.tar.gz

The actual file is nws_precip_conus_20081101.nc It's apparent that the 
file cannot be read directly with GRADS using sdfopen due to the error 
message:

      gadsdf: SDF file has no discernable X coordinate.

So I've tried creating a GRADS ctl file so that the data can be read 
with the "open" function.  I'm fairly sure that I'm not correctly 
creating the GRADS control file as I either get error messages about the 
lat/lon bounds or when I try to plot, the message is "Cannot contour 
grid - all undefined values".

There is a C program available at the same web site to convert the data 
to a lat/lon grid and I'm also working on compiling that code, but it 
seems that it should be easy to read the netcdf file with GRADS.  I've 
also searched on the web for an existing control file that could be used 
as a template, assuming that other folks would be displaying RADAR data 
using GRADS, but I've come up empty handed.

Does anyone have a control file they could share or offer suggestions on 
what should be in the control file?  (If I dump all the data with ncdump 
it's apparent that there is data in the file in the correct units, and 
the data also contains the values "-1" and "-2" to delineate ocean and 
missing data value.)

Wayne Gibson
Oregon State University

------------------------------------------------------------------------------------------------
GRADS version: 2.0.a8
Operating System: Linux 2.6.18-164
Version ncdump: 2.6.2 SUN

ncdump -c nws_precip_conus_20081101.nc
netcdf nws_precip_conus_20081101 {
dimensions:
        hrapy = 813 ;
        hrapx = 1051 ;
        latlong = 4 ;
        dates = 11 ;
variables:
        short amountofprecip(hrapy, hrapx) ;
                amountofprecip:long_name = "24-Hour Rainfall" ;
                amountofprecip:units = "1/100 mm" ;
                amountofprecip:grid = "hrap_grid=polar stereograph 
projection" ;
                amountofprecip:resolution = "4km*4km" ;
                amountofprecip:dateofdata = "2008110112Z" ;
                amountofprecip:dateofcreation = "2008110221Z" ;
                amountofprecip:location = "continental united states" ;
                amountofprecip:author = "national weather service rfcs 
genereated by program ROUT" ;
                amountofprecip:comments = "preliminary data...subject to 
change" ;
        float lat(latlong) ;
                lat:order = "bottom_left,bottom_right,top_right,top_left" ;
        float lon(latlong) ;
                lon:order = "bottom_left,bottom_right,top_right,top_left" ;
        float true_lat ;
        float true_lon ;
        char timeofdata(dates) ;
        char timeofcreation(dates) ;
        float hrap_xor ;
                hrap_xor:comments = "offset in x direction of hrap grid" ;
        float hrap_yor ;
                hrap_yor:comments = "offset in x direction of hrap grid" ;
data:
}