[Met_help] polyline define

John Halley Gotway johnhg at ucar.edu
Mon Apr 26 16:45:41 MDT 2010


(1) Yes, it looks like a leading space causes a problem.  I'd suggest removing any leading spaces.

(2) I'm not exactly sure what you're trying to tell me here.  Using the -subtract option to compute 72hr - 48hr = 24 hours of accumulation for ARW is fine.  Is there a problem in how the
initialization and valid times are being stored?


Segayle Thompson wrote:
> Hi John,
> Thanks for the quick response.
> 2 questions
> 1) If the *.poly file has a leading space will that cause a problem?
> 2) I believe that the forecast is much better than the RMSE is
> indicating. Since I am working with ARW I used PCP tool to subtract one
> forecast time from another. So For example, I have a 72hr forecast and a
> 48 hr forecast and I subtract them this provides me with the forecast
> precip between 48 and 72hr. When I use the pcptool and subtract or sum
> my initial time and my valid time are always the same.
> On Apr 26, 2010, at 3:52 PM, John Halley Gotway wrote:
>> Segayle,
>> 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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