[gradsusr] NAM and APCPSFC data

Fri Oct 14 20:09:42 EDT 2016

Thanks Jennifer.  I wrote something similar and it appears to be working.  
Appreciate everyone's help!  Many thanks. 

On October 14, 2016 12:40:16 PM PDT, Jennifer M Adams <jadams21 at gmu.edu> wrote:
>Mark,
>Below is the bit of code I use to ’normalize' precip accumulations from
>the GFS for the meteograms. (I write out a new file.) The records
>alternate between 3hr and 6hr accumulations, so you may have to adapt
>for your data and your particular needs. The full code source is
>ftp://cola.gmu.edu/pub/jma/meteograms/meteogram_subset_GDS.gs
>—Jennifer
>p.s. I also use t=1 as the initialization time and p is alwasy
>undefined at t=1, but I write it out anyway.
>
>* Write out the precip variables
>'set fwrite mysubsetp.dat'
>'set t 1'
>'d p'
>t=2
>while (t<=tmax-1)
>* these are 3-hourly accumulations
>  'set t 't
>  'd p'
>* these are 6-hourly accumulations
>* so we must subtract the previous 3hr totals
>  'set t 't+1
>  'd p-p(t-1)  '
>  t=t+2
>endwhile
>'disable fwrite’
>
>
>
>On Oct 14, 2016, at 1:49 PM, Mark Sponsler
><msponsler at COMCAST.NET<mailto:msponsler at COMCAST.NET>> wrote:
>
>Thanks Jeff!  Perfect - that is what I needed.
>Let me go play with my script. Bet I made a logic error somewhere.
>Thanks again!
>Thanks,
>Mark
>----- Original Message -----
>From: Jeff Duda <jeffduda319 at gmail.com<mailto:jeffduda319 at gmail.com>>
>To: GrADS Users Forum
><gradsusr at gradsusr.org<mailto:gradsusr at gradsusr.org>>
>Sent: Fri, 14 Oct 2016 17:32:12 -0000 (UTC)
>Subject: Re: [gradsusr] NAM and APCPSFC data
>'set t 2'
>'d apcpsfc'
>should display 1-hr precip accumulation between f00 and f01
>'set t 3'
>'d apcpsfc'
>should display 2-hr precip accumulation between f00 and f02
>'set t 4'
>'d apcpsfc'
>should display 3-hr precip accumulation between f00 and f03
>'set t 5'
>'d apcpsfc'
>should display 1-hr precip accumulation between f03 and f04
>...
>...
>...
>and so on.
>If you want to display 1-hr precip at "off" hours (not f01, f04, f07,
>...) then yes, you need to display the difference over consecutive
>hours.
>f02: 'set t 3' ; 'd apcpsfc - apcpsfc(t-1)'
>f03: 'set t 4' ; 'd apcpsfc - apcpsfc(t-1)'
>Notice how the pattern is the same despite the particular time. The
>only exception is at f01, f04, f07, ... when you just display apcpsfc
>without any subtraction.
>You appear to have this idea. Is this not getting you the results you
>expect?
>Jeff
>
>On Fri, Oct 14, 2016 at 12:26 PM, Mark Sponsler
><msponsler at comcast.net<mailto:msponsler at comcast.net>> wrote:
>Hi Jeff,
>Thanks for the info.
>Yeah, I use the first time step which of course has no precip data in
>it. So the cycle would start with t = 2.
>Just to confirm, for either the 1 hr NAM or the 3 hr NAM, I simply
>should use the below logic and all should be good?
>In other words, the 1 hr NAM accumulates in 3 time step sequential
>bundles (timesteps 2,3,4 refresh then 5,6,7, refresh etc) and the 3 hr
>NAM accumulates the same.
>Display Time = 2
>Time 3 = Time 3 - Time 2
>Display Time 3
>Time 4 = Time 4 - Time 3
>Display Time 4
>Display Time = 5
>Time 6 = Time 6 - Time 5
>Display Time 6
>Time 7 = Time 7 - Time 6
>Display Time 7
>etc...
>Thanks,
>Mark
>----- Original Message -----
>From: Jeff Duda <jeffduda319 at gmail.com<mailto:jeffduda319 at gmail.com>>
>To: GrADS Users Forum
><gradsusr at gradsusr.org<mailto:gradsusr at gradsusr.org>>
>Sent: Fri, 14 Oct 2016 16:59:14 -0000 (UTC)
>Subject: Re: [gradsusr] NAM and APCPSFC data
>Mark,
>
>Why do you not think it works the way you described in (1)? That's the
>way I've always used it, and I've never had a problem. The particular
>t-index value you use in grads depends on how you setup the control
>file. If you didn't start the time index at forecast hour 0, then there
>will be a phase difference between what you think and what actually
>works.
>
>Jeff Duda
>
>On Fri, Oct 14, 2016 at 10:55 AM, Mark Sponsler
><msponsler at comcast.net<mailto:msponsler at comcast.net>> wrote:
>Hi,
>I'm trying to display variable 'apcpsfc' from the 3 hr and 1 hr NAM. 
>The resulting images appear to pulsate/accumulate precip every few
>images then reset only to accumulate again.
>
>I've seen the threads in the archive on this issue with HD GFS data,
>but I'm trying to understand 2 things:
>
>1) What is the accumulation period for NAM 1 hr and 3 hr data.  I was
>thinking it was every 3 time steps (i.e. excluding time step 1 / 00
>hr), it is 2, 3, 4 then reset and start accumulating again for the next
>3 time steps 5, 6 and 7).  But that doesnt seem to be the case.
>
>2) What does it mean to 'normalize' the data? Westly did something in
>wgrib2 for HD GFS data to normalize it and I was wondering if that was
>also applicable to NAM data.  What is done to mathmatically to get the
>data to be valid for just a single timestep?.  Can I write something in
>GRDADS to perform the normalization rather than having to use WGRIB2.
>
>Assuming the accumulation theory is correct (that apcpsfc accumulates
>every three time steps), I've been trying to write code to remove the
>accumulation by:
>
>Display Time = 2
>Time 3 = Time 3 - Time 2
>Display Time 3
>Time 4 = Time 4 - Time 3
>Display Time 4
>
>But it doesnt work.
>
>Any help would be appreciated.
>
>Thanks,
>Mark
>Thanks,
>Mark
>
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>
>--
>Jeff Duda
>Post-doctoral research associate
>University of Oklahoma School of Meteorology
>
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>
>--
>Jeff Duda
>Post-doctoral research associate
>University of Oklahoma School of Meteorology
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>--
>Jennifer Miletta Adams
>Center for Ocean-Land-Atmosphere Studies (COLA)
>George Mason University
>
>
>
>
>
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Thanks,
Mark Sponsler
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