[Met_help] polyline define

John Halley Gotway johnhg at ucar.edu
Mon Apr 26 13:52:32 MDT 2010


In order to know for sure, I'd need to see the file that defines your polyline region.  However, based on the error message, I'm guessing that the name you chose to give the polyline contains
"illegal" characters.  The polyine file should consist of a name for the polyline followed by the lat/lon values that define it.  You can look at the file "METv2.0/data/poly/CONUS.poly" for an
example.  The name you choose cannot begin with a number and should probably only contain standard characters like letters, numbers, underscores, and dashes.

Also, please be aware that you do NOT have to run gen_poly_mask to use a lat/lon masking region.  You can use the lat/lon polyline file directly in Grid-Stat if you'd like.  See the file
"METv2.0/scripts/config/GridStatConfig_APCP_12" for an example of that.  However, if you're going to apply the masking region many times, it is a good idea to run it through gen_poly_mask first since
that'll allow Grid-Stat to run faster.

And lastly, why is your RMSE very high?  My first guess is that it's just a bad forecast.  One thing you could do is take a look at the NetCDF matched pairs output from Grid-Stat.  You turn on the
generation of that file by setting the last value in the "output_flag" parameter in the Grid-Stat config file.  You can use "ncview" to take a look at the gridded forecast, observation, and difference
fields.  If the difference field contains large value then your RMSE values will be large as well.

Hope that helps.

John Halley Gotway
met_help at ucar.edu

Segayle Thompson wrote:
> Hello,
> I am trying to verify APCP (accumulated precip) using Stage IV  
> observation data, but I seem to be having problems with 2 things.
> 1) I am trying to create a polyline for my region -so I have a file  
> with lat and long but when I try to run gen_poly_mask.sh I get an  
> error that says
> ncvardef:ncid 3: Attribute or variable name contains illegal characters
> What is causing this error and how do I fix it?
> 2) The reason I am trying to do an poly_mask is because when I run  
> grid_stat without it my RMSE values are very high. What could there be  
> other reasons for this high errors (other than I need to generate my  
> own poly_mask?)
> segayle
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