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<DIV><FONT face=Arial size=2>Hi Dan</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Different model grib files store accumulated
precip in different ways. Some give you the accumulation over the period from
the last timestep to the current one (like what I think you want) .Others do it
a bit differently , for example;</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>T+6 (6hr accum)</FONT></DIV>
<DIV><FONT face=Arial size=2>T+12 (12 hr accum)</FONT></DIV>
<DIV><FONT face=Arial size=2>T+18 (6hr accum)</FONT></DIV>
<DIV><FONT face=Arial size=2>T+24(12 hr accum)</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Other model grib files are different yet again
; some give you an accumulation as a running total through the model
forecast time periods (so accum-precip at 48 hr is in fact from
0-48hr).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>This can introduce some quirks into how you deal
with the data. In my case, I always pre-process the data so that I have the
precip in _my_ desired temporal resolution before I try to display it ,
depending on what I'm trying to do. e.g. in some cases I want to show 24 hours
amounts, so first I break it down into accumulation over the interval (prev-step
to current-step) like you want, then add 'em all up to give me the 24 hour
amounts at whichever timestep I want. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT><FONT face=Arial size=2></FONT> </DIV>
<DIV>
<DIV><FONT face=Arial size=2>You can get an idea of how your model grib files
are storing the precip accumulation by doing a wgrib -v on the file and having a
look at the output.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Unfortunately I don' t know if Grads has any
built-in capability to handle the accumulated precip in a standard
way.</FONT></DIV></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Hope this helps</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Regards</FONT></DIV>
<DIV><FONT face=Arial size=2>Iain</FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=theedge981@GMAIL.COM href="mailto:theedge981@GMAIL.COM">Dan Leins</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=GRADSUSR@LIST.CINECA.IT
href="mailto:GRADSUSR@LIST.CINECA.IT">GRADSUSR@LIST.CINECA.IT</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, November 13, 2005 7:06
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> 3 or 6 hourly precip from girb
files...</DIV>
<DIV><BR></DIV>
<DIV>To all,</DIV>
<DIV> </DIV>
<DIV>I've been trying to use GrADS to plot 3 or 6 hourly precip plots
(depending on what the model timesteps are), but been uncussessful thus
far. I've used grib2ctl.pl to dump my model grib files to a control file
and gone from there, with the only precip options being... </DIV>
<DIV> </DIV>
<DIV>acpcpsfc (convective precip), apcpsfc (surface total precip), and
ncpcpsfc (large scale precip). Another one deals with precip rate, but
I'm not interested in that.</DIV>
<DIV> </DIV>
<DIV>I'm simply interested in how much precip fell between the previous model
timestep and the one I'm working with, but using each of these options simply
increments the precip through all 48 hours - like a running total. So if
it rains from hours 03-09 - and is dry after that, I still see precip being
output for hours 12-48 even if it's not going to rain. Does anyone have
any idea how to plot the precip that fell ONLY during the time valid in the
grib file? </DIV>
<DIV> </DIV>
<DIV>I don't know if it helps or anything, but when creating the idx file
- I use the -0 and -v options - maybe that makes a difference...</DIV>
<DIV> </DIV>
<DIV>Thanks,</DIV>
<DIV>Dan Leins</DIV></BLOCKQUOTE></BODY></HTML>