[Met_help] MODE inputs

John Halley Gotway johnhg at rap.ucar.edu
Thu Feb 19 12:50:53 MST 2009


OK, I understand your question now.  You'll want to use a combination of WPP and the PCP-Combine tool in MET.

Suppose you're running your WRF-ARW model and creating an output file every 3 hours out to 24 hours.  So it'll write files every 3 hours that be default contain precipitation accumulated up until that
time.  So the 12 hour file will contain precip accumulated over 12 hours.  And the 15 hour file will contain precip accumulated over 15 hours.  When you run these files through WPP, corresponding GRIB
files will be created using the same accumulation intervals.

Then you can run the PCP-Combine tool on those GRIB files using the "-subtract" option.  That will allow you to "subtract" the 12 hour accumulation from the 15 hour accumulation, yielding a 3 hour
accumulation.  You can refer to the MET User's Guide for details on running the "-subtract" option.  We put in the "-subtract" option for the very reason your asking about.

However, you won't be able to verify 1 hour accumulations unless you're writing a WRF-out file every hour.

Hope that helps.


Holmberg, Shelley wrote:
> Mr. Gotway,
> Sorry if I was not clear before.  My problem is getting the correct accumulation period for the total accumulated precipitation in the wrfout file.  Right now, the precipitation accumulates over 22 hours and I would like to have 1 hour (or 3 hour) accumulations for each of the 22 hours.  The variable "Accumulated total precipitation," Grib 61 will work prefectly but is it possible to get the right accumulation period with the WPP?
> Thank you!
> Shelley
> -----Original Message-----
> From: John Halley Gotway [mailto:johnhg at rap.ucar.edu]
> Sent: Wed 2/18/2009 6:08 PM
> To: Holmberg, Shelley
> Cc: met_help at ucar.edu
> Subject: Re: [Met_help] MODE inputs
> Shelley,
> Let me see if I understand your situation correctly.  You are running the
> WRF-ARW model and are generating WRF NetCDF output files.  You're running
> those NetCDF output files through the WRF Post-Processor (WPP) and
> generating GRIB files.  Then you trying to use the PCP-Combine tool in MET
> to combine the precipitation fields.
> Please note that PCP-Combine currently only reads GRIB files.  So you'd
> need to run your WRF output through WPP prior to running MET.
> You say that you'd like to combine RAINC and RAINNC from the model.  Now
> I'm not sure when you run your data through WPP, how does it write those
> fields out?  Perhaps they're written as large scale precip (NCPCP) and
> convective precip (ACPCP).
> And your question is this: Is there a way to get PCP-Combine to add
> together NCPCP and ACPCP?  The short answer is no, not currently.
> But if I understand correctly, I'm wondering why don't you just use the
> accumulated precipitation field, APCP (i.e. GRIB code 61)?  The StageIV
> analysis, against which you're verifying, is accumulated precip (code 61).
>  Is there a reason that you'd like to combine RAINC and RAINNC, rather
> than just using accumulated precip directly?
> If there is some reason why combining these two precip types makes sense,
> we could probably add support for it to the PCP-Combine tool.
> Do I understand the situation correctly?  Does verifying APCP accomplish
> what you're trying to do?
> Thanks,
> John Halley Gotway
> johnhg at ucar.edu
>> Hi!
>> I have been working with the MODE tool within MET off and on for a year
>> now.  I have to tool properly configured as it will work with the canned
>> data and some of my own data.  My main issue is that I am trying to
>> compare 1 or 3 hour surface accumulations of rainfall from WRF output
>> (convective and grid scale) and Stage IV observations.  I have
>> successfully used copygb and pcp_combine to format the Stage IV obs. but
>> with the modeled data, I haven't been able to: add the rainc and rainnc
>> variables; get the proper accumulation period; and then write out a netcdf
>> or GRIB file.  Is there a program available that will properly process my
>> modeled data?
>> Thank you!
>> Shelley
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