[Met_help] [rt.rap.ucar.edu #44250] History for Averaging question

[RAL HelpDesk {for John Halley Gotway}]

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  Initial Request
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Hello John-

 

I hope this email finds you well.  I have a quick question regarding the
PCP-Combine tool in the MET software.

 

We are trying to take 50 gridded files and average them into a single
file.  The PCP-Combine tool sums, averages and subtracts.  Is there a
quick and dirty way we could get it to do an average?

 

Also, to elaborate on these 50 files...each file stores 365 days of
global maximum temperature obs.  So basically what we are trying to do
is create one gridded file with a 50-year average of the maximum
temperature for each day of the year.  

 

We are considering writing our own script for this, but just wanted to
see if there was an easier way to do this through MET before we go down
that road.

 

Thanks!

Holly



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  Complete Ticket History
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Subject: Re: [rt.rap.ucar.edu #44250] Averaging question
From: John Halley Gotway
Time: Wed Feb 09 16:07:35 2011

Holly,

I created a MET-Help ticket for this just so we can track our user
support.

I assume your 50 files are in GRIB format, is that correct?

If I were in your position, I think I'd use the MET Ensemble-Stat tool
(in METv3.0) to compute the averages.  However, it'll yield one file
for each day of the year, not one file containing all 365
days.  You'd need to run Ensemble-Stat 365 times, once for each day of
the year.  I don't know how the timing info in your GRIB records are
defined, but you may be able to use the "-ens_lead" command
line argument to tell Ensemble-Stat which of the 365 records to use
for the current run.  If that doesn't work, it'd get messier.

One of the output fields from Ensemble-Stat is the ensemble mean value
- which in your case would be the mean of the 50 years.

Alternatively, you could modify the pcp_combine code to dump out an
average rather than sum, but that'd require you to modify the source
code.

That's at least somewhere to start.

John

On 02/09/2011 04:06 PM, RAL HelpDesk {for John Halley Gotway} wrote:
>
> Wed Feb 09 16:06:00 2011: Request 44250 was acted upon.
> Transaction: Ticket created by johnhg
>        Queue: met_help
>      Subject: Averaging question
>        Owner: johnhg
>   Requestors: hhassenzahl at wxc.com
>       Status: new
>  Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=44250 >
>
>
> Hello John-
>
>
>
> I hope this email finds you well.  I have a quick question regarding
the
> PCP-Combine tool in the MET software.
>
>
>
> We are trying to take 50 gridded files and average them into a
single
> file.  The PCP-Combine tool sums, averages and subtracts.  Is there
a
> quick and dirty way we could get it to do an average?
>
>
>
> Also, to elaborate on these 50 files...each file stores 365 days of
> global maximum temperature obs.  So basically what we are trying to
do
> is create one gridded file with a 50-year average of the maximum
> temperature for each day of the year.
>
>
>
> We are considering writing our own script for this, but just wanted
to
> see if there was an easier way to do this through MET before we go
down
> that road.
>
>
>
> Thanks!
>
> Holly
>

------------------------------------------------
Subject: RE: [rt.rap.ucar.edu #44250] Averaging question
From: hhassenzahl at wxc.com
Time: Wed Feb 09 16:17:00 2011

Thanks for your quick response, John.  The Ensemble Stat tool is good
to
know about (I need to get more familiar with v3.0!).

I think we're going to code this on our own...it should only take a
couple hours on our end (hopefully) to get a working script.  I'll let
you know if that fails and we decide to try the MET route.

Thanks again!  Hope you're well,
Holly

________________________________
Holly C. Hassenzahl
Science Analyst, Meteorologist
Data Products Group
Weather Central, LLC
401 Charmany Drive
Madison, WI 53719
(608)274-5789 ext 288

-----Original Message-----
From: RAL HelpDesk {for John Halley Gotway} [mailto:met_help at ucar.edu]
Sent: Wednesday, February 09, 2011 5:08 PM
To: Holly Hassenzahl
Subject: Re: [rt.rap.ucar.edu #44250] Averaging question

Holly,

I created a MET-Help ticket for this just so we can track our user
support.

I assume your 50 files are in GRIB format, is that correct?

If I were in your position, I think I'd use the MET Ensemble-Stat tool
(in METv3.0) to compute the averages.  However, it'll yield one file
for
each day of the year, not one file containing all 365
days.  You'd need to run Ensemble-Stat 365 times, once for each day of
the year.  I don't know how the timing info in your GRIB records are
defined, but you may be able to use the "-ens_lead" command
line argument to tell Ensemble-Stat which of the 365 records to use
for
the current run.  If that doesn't work, it'd get messier.

One of the output fields from Ensemble-Stat is the ensemble mean value
-
which in your case would be the mean of the 50 years.

Alternatively, you could modify the pcp_combine code to dump out an
average rather than sum, but that'd require you to modify the source
code.

That's at least somewhere to start.

John

On 02/09/2011 04:06 PM, RAL HelpDesk {for John Halley Gotway} wrote:
>
> Wed Feb 09 16:06:00 2011: Request 44250 was acted upon.
> Transaction: Ticket created by johnhg
>        Queue: met_help
>      Subject: Averaging question
>        Owner: johnhg
>   Requestors: hhassenzahl at wxc.com
>       Status: new
>  Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=44250
>
>
>
> Hello John-
>
>
>
> I hope this email finds you well.  I have a quick question regarding
the
> PCP-Combine tool in the MET software.
>
>
>
> We are trying to take 50 gridded files and average them into a
single
> file.  The PCP-Combine tool sums, averages and subtracts.  Is there
a
> quick and dirty way we could get it to do an average?
>
>
>
> Also, to elaborate on these 50 files...each file stores 365 days of
> global maximum temperature obs.  So basically what we are trying to
do
> is create one gridded file with a 50-year average of the maximum
> temperature for each day of the year.
>
>
>
> We are considering writing our own script for this, but just wanted
to
> see if there was an easier way to do this through MET before we go
down
> that road.
>
>
>
> Thanks!
>
> Holly
>


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Subject: Re: [rt.rap.ucar.edu #44250] Averaging question
From: John Halley Gotway
Time: Wed Feb 09 16:18:41 2011

Holly,

Sounds good.  It should be pretty straightforward.  If you're familiar
with NCL, you may find it helpful for this sort of thing.  Of course,
there are any number of other tools that'd work too.

Thanks,
John

On 02/09/2011 04:17 PM, RAL HelpDesk {for hhassenzahl at wxc.com} wrote:
> Thanks for your quick response, John.  The Ensemble Stat tool is
good to

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