[Met_help] [rt.rap.ucar.edu #61523] History for Using pcp_combine to created files for Mode tool

[John Halley Gotway via RT]

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  Initial Request
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Hello,

I am attempting to create precip accumulation files for input into the MET
mode tool using the pcp_combine tool. I am taking two GRIB files and
subtracting one from the other, but when I run pcp_combine thusly:

pcp_combine \
-subtract \
/nfs4/mi_tmdl/WRFGRB/wrfout_d02_2005-01-01_12:00:00.grb 12 \
/nfs4/mi_tmdl/WRFGRB/wrfout_d02_2005-01-01_06:00:00.grb 6 \
/data/wrf/wrf_mode/wrf_pcp_d02_2005_01_01_12_6hr

I get this error:

ERROR: get_field() -> can't find grib code 61 with accumulation of 120000
in GRIB file: /nfs4/mi_tmdl/WRFGRB/wrfout_d02_2005-01-01_12:00:00.grb

However, when I use the wgrib command to look at
/.../wrfout_d03_2005-01-01_12:00:00.gb, I find this information:

278:19207484:d=04123100:APCP:kpds5=61:kpds6=1:kpds7=0:TR=4:P1=0:P2=36:TimeU=1:sfc:0-36hr
acc:NAve=0

Since the variable is APCP, or accumulated precip, I take this to be the
pertinent grib code. Am I missing some syntax, or am I doing something
wrong to run this tool?

Thank you for your help,

-- 
Zachary Ebenstein
University of Michigan
College of Engineering
Dept. Atmospheric, Oceanic and Space Sciences
Climate Physics (B.S.E), Dec. 2011


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  Complete Ticket History
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Subject: Re: [rt.rap.ucar.edu #61523] Using pcp_combine to created files for Mode tool
From: John Halley Gotway
Time: Thu May 23 14:55:56 2013

Zac,

I see that you're using pcp_combine to perform a subtraction command
in order to compute a 6-hour accumulation of precipitation.

Running wgrib on the input files to see what they contain is a great
thing to do!  And reading the wgrib output you sent, I see that that
file contains a 0-36 hour accumulation.  See the "0-36hr acc"
in the wgrib output:
    278:19207484:d=04123100:APCP:kpds5=61:kpds6=1:kpds7=0:TR=4:P1=0:P2=36:TimeU=1:sfc:0-
36hr acc:NAve=0

However, when you run pcp_combine, you're asking it to find a 12-hour
accumulation.  It errors out because that file contains a 36-hour
accumulation, not 12-hours.  I suspect the following command
will do what you want:

pcp_combine \
-subtract \
/nfs4/mi_tmdl/WRFGRB/wrfout_d02_2005-01-01_12:00:00.grb 36 \
/nfs4/mi_tmdl/WRFGRB/wrfout_d02_2005-01-01_06:00:00.grb 30 \
/data/wrf/wrf_mode/wrf_pcp_d02_2005_01_01_12_6hr

I'm guessing the confusion here is coming from the naming convention
of the wrfout files.  They contain the valid time stamp in their names
- not the forecast lead time.  You probably saw that the
files were valid at 12:00:00 and 06:00:00 and assumed they were from
the initialization at 00Z that day.  But they must have been from the
previous day's initialization since they contain 36 and
30-hour accumulations.

Make sense?

Thanks,
John Halley Gotway
met_help at ucar.edu

On 05/23/2013 11:04 AM, Zachary Ebenstein via RT wrote:
>
> Thu May 23 11:04:56 2013: Request 61523 was acted upon.
> Transaction: Ticket created by ebenszac at umich.edu
>         Queue: met_help
>       Subject: Using pcp_combine to created files for Mode tool
>         Owner: Nobody
>    Requestors: ebenszac at umich.edu
>        Status: new
>   Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=61523 >
>
>
> Hello,
>
> I am attempting to create precip accumulation files for input into
the MET
> mode tool using the pcp_combine tool. I am taking two GRIB files and
> subtracting one from the other, but when I run pcp_combine thusly:
>
> pcp_combine \
> -subtract \
> /nfs4/mi_tmdl/WRFGRB/wrfout_d02_2005-01-01_12:00:00.grb 12 \
> /nfs4/mi_tmdl/WRFGRB/wrfout_d02_2005-01-01_06:00:00.grb 6 \
> /data/wrf/wrf_mode/wrf_pcp_d02_2005_01_01_12_6hr
>
> I get this error:
>
> ERROR: get_field() -> can't find grib code 61 with accumulation of
120000
> in GRIB file: /nfs4/mi_tmdl/WRFGRB/wrfout_d02_2005-01-
01_12:00:00.grb
>
> However, when I use the wgrib command to look at
> /.../wrfout_d03_2005-01-01_12:00:00.gb, I find this information:
>
>
278:19207484:d=04123100:APCP:kpds5=61:kpds6=1:kpds7=0:TR=4:P1=0:P2=36:TimeU=1:sfc:0-
36hr
> acc:NAve=0
>
> Since the variable is APCP, or accumulated precip, I take this to be
the
> pertinent grib code. Am I missing some syntax, or am I doing
something
> wrong to run this tool?
>
> Thank you for your help,
>

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