Confused by coordinate variable

Hello NCL-Talk,

I'm perpetually confused by coordinate variables. I need to create a cross-section of relative humidity between two points using NAM-218 data. I am trying to borrow code from the transect example, http://www.ncl.ucar.edu/Applications/Scripts/trans_1.ncl, but it uses linint2_points, which I believe requires coordinate variables. When I run ncl_filedump on the NAM-218 grib file, I get information like:

 float R_H_218_ISBL ( lv_ISBL2, gridx_218, gridy_218 )
         center : US National Weather Service - NCEP (WMC)
         long_name : Relative humidity
         units : %
         _FillValue : 1e+20
         coordinates : gridlat_218 gridlon_218
         level_indicator : 100
         grid_number : 218
         parameter_table_version : 2
         parameter_number : 52
         model : MESO ETA Model
         forecast_time : 0
         forecast_time_units : hours
         initial_time : 12/11/2008 (12:00)

and for gridlat_218:

      float gridlat_218 ( gridx_218, gridy_218 )
         corners : ( 12.19, 14.35541, 57.34082, 54.56082 )
         long_name : latitude
         grid_description : AWIPS grid over the Contiguous United States (us
ed by the 12-km ETA Model) (Lambert Conformal)
         units : degrees_north
         mpLambertMeridianF : 265
         mpLambertParallel2F : 25
         mpLambertParallel1F : 25
         mpProjection : LAMBERTCONFORMAL
         Dy : 12190.58
         Dx : 12190.58
         Lov : 265
         Lo1 : 226.514
         La1 : 12.19

So my question is, what coordinate variables should I use in linint2_points and how do I create them? Sorry for the dumb question.

Thanks,

Jim
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Received on Sun Aug 4 23:47:18 2013