[Met_help] [rt.rap.ucar.edu #58534] History for about accumulated precipitation

[John Halley Gotway via RT]

----------------------------------------------------------------
  Initial Request
----------------------------------------------------------------

Hello,
I run WRF model for 72-hours. How can I modify WRF outputs that it has accumulated precipitation for 0-12hours, 12-24hours, 24-36hours and 36-48hours in grib format and my new files only include accumulated precipitation?
I would like my new outputs to be in grib format. How can I do that?
Please help me,
Thanks,

----------------------------------------------------------------
  Complete Ticket History
----------------------------------------------------------------

Subject: Re: [rt.rap.ucar.edu #58534] about accumulated precipitation
From: John Halley Gotway
Time: Mon Oct 01 07:52:52 2012

Hello,

Since your output contains a runtime accumulation of precipitation, I
assume that you're running the WRF-ARW model.  It sounds like you'd
like to break that runtime accumulation down into smaller
accumulations intervals.  There are a few pieces of information that
may be helpful.

First, when you run WRF-ARW, you could configure it to dump out
precipitation every 12-hours.  By default, precipitation is
accumulated over the entire model run, but you can set the "bucket_mm"
namelist option to specify a shorter time interval if you'd like.
Take a look at page 5-34 of the WRF-ARW users guide for more
information
(www.mmm.ucar.edu/wrf/users/docs/user_guide_V3/ARWUsersGuideV3.pdf).

Second, you could use the pcp_combine tool within MET
(http://www.dtcenter.org/met/users/support/online_tutorial/METv4.0/pcp_combine/index.php)
to perform addition and subtraction operations for
precipitation.  MET works best when dealing with gridded data files in
GRIB format.  We recommend that WRF users post-process their model
output using the Unified Post-Processor (UPP).  The output of
UPP is in GRIB format.  Then, when you run the GRIB files through the
MET pcp_combine tool, it's output is in NetCDF format.  The NetCDF
output of pcp_combine can then be used as input to the other
MET verification tools.  Here's an example of using pcp_combine to
perform a subtraction operation:

    pcp_combine -subtract file1.grb 36 file2.grb 24 apcp_36_24.nc

It will look in file1.grb and file2.grb for 36-hour and 24-hour
accumulations of precipitation and then take their difference.

Lastly, there's a set of tools out there called the NetCDF Operators,
or NCO (http://nco.sourceforge.net).  It's a set of command-line tools
for performing operations on NetCDF files.  I have very
little experience using them, but you might be able to use them to
take a difference if you wanted to operate on the raw NetCDF output of
WRF.

Hope that helps lay out some options for you.

Thanks,
John Halley Gotway
met_help at ucar.edu

On 09/30/2012 02:16 AM, M M via RT wrote:
>
> Sun Sep 30 02:16:25 2012: Request 58534 was acted upon.
> Transaction: Ticket created by weather1388 at yahoo.com
>         Queue: met_help
>       Subject: about accumulated precipitation
>         Owner: Nobody
>    Requestors: weather1388 at yahoo.com
>        Status: new
>   Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=58534 >
>
>
> Hello,
> I run WRF model for 72-hours. How can I modify WRF outputs that it
has accumulated precipitation for 0-12hours, 12-24hours, 24-36hours
and 36-48hours in grib format and my new files only include
accumulated precipitation?
> I would like my new outputs to be in grib format. How can I do that?
> Please help me,
> Thanks,
>

------------------------------------------------