<div>Hi Jeff,</div>
<div>Thanks for the info. </div>
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<div>Yeah, I use the first time step which of course has no precip data in it. So the cycle would start with t = 2.</div>
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<div>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?</div>
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<div>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. </div>
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<div>Display Time = 2<br />Time 3 = Time 3 - Time 2<br />Display Time 3<br />Time 4 = Time 4 - Time 3<br />Display Time 4</div>
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<div>Display Time = 5</div>
<div>Time 6 = Time 6 - Time 5</div>
<div>Display Time 6</div>
<div>Time 7 = Time 7 - Time 6</div>
<div>Display Time 7</div>
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<div>etc...</div>
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<div><span style="font-size: small;">Thanks,<br />Mark</span></div>
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<div>----- Original Message -----<br />From: Jeff Duda <jeffduda319@gmail.com><br />To: GrADS Users Forum <gradsusr@gradsusr.org><br />Sent: Fri, 14 Oct 2016 16:59:14 -0000 (UTC)<br />Subject: Re: [gradsusr] NAM and APCPSFC data</div>
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<div>Mark,</div>
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.<br />
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Jeff Duda</div>
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<div class="gmail_quote">On Fri, Oct 14, 2016 at 10:55 AM, Mark Sponsler <span dir="ltr"><<a href="mailto:msponsler@comcast.net" target="_blank">msponsler@comcast.net</a>></span> wrote:<br />
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<div>Hi,<br />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.<br />
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I've seen the threads in the archive on this issue with HD GFS data, but I'm trying to understand 2 things:<br />
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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. <br />
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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. <br />
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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:<br />
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Display Time = 2<br />Time 3 = Time 3 - Time 2<br />Display Time 3<br />Time 4 = Time 4 - Time 3<br />Display Time 4<br />
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But it doesnt work. <br />
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Any help would be appreciated.<br />
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Thanks,<br />Mark </div>
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<div><span style="font-size: small;">Thanks,<br />Mark</span></div>
<br />_______________________________________________<br />
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<br /><br clear="all" /><br />-- <br />
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<div>Jeff Duda<br />Post-doctoral research associate<br />University of Oklahoma School of Meteorology</div>
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