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<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>Eduardo,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>Glad to see that you are working with the adaptive
time-step. As I'm sure you know, it is new in WRF3.0. We developed
and have been using the adaptive time-step in operational forecasts with a
modified version of WRF2.2 for quite some time. Our operational
simulations consist of an outer 12km nest and an inner 4km nest.
This configuration has been very stable for us. However, we have only done
limited testing with three levels of nesting.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>I'm interested to see the length of the time-steps just
before the model crash. Could you post the last hundred or so "Timing for
main" lines from the rsl.out.0000 file?</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>Have you set any parameters in the namelist file other than
the use_adaptive_time_step setting?</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>I'd suggest that you add the following to your namelist
file:</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>max_step_increase_pct = 5, 51, 51 (the default
is 5,5,5)</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>This will limit the time-step of the outer nest from
changing by more than 5%, but allow the time-step on the inner two nests to
change by up to 51%. Since the inner nest(s) time steps must be evenly
divisible into the outer nest time-step, with the default of 5,5,5, the time
step on the inner nests will not increase unless the time-step on the outer
nest changes. </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>Just FYI:</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>I believe the 'WOULD GO OFF TOP" lines that you see are a
symptom of the model being unstable. I've seen these types of errors in
several situations:</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>1) a couple of minutes into a simulation -- often this is
caused by bad input data</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=440004713-20062008><FONT face=Arial
color=#0000ff size=2>2) later on during a simulation -- this is most often
caused by a time-step problem, or bad boundary data.</FONT></SPAN></DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> wrf-users-bounces@ucar.edu
[mailto:wrf-users-bounces@ucar.edu] <B>On Behalf Of </B>Eduardo Penabad
Ramos<BR><B>Sent:</B> Tuesday, June 17, 2008 11:37 AM<BR><B>To:</B>
wrf-users@ucar.edu<BR><B>Cc:</B> 'wrfhelp'<BR><B>Subject:</B> [Wrf-users] Tests
with adaptive time step in WRF-ARW (v3)<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial
size=2>Hello!</FONT></SPAN></DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial size=2>we are running a
setup of 3 nested grids with WRF-ARW (v3) over Galicia (NW Iberian Peninsula),
with dx=36,12 and 4 km.</FONT></SPAN></DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial size=2>We are testing the
adaptive time step with this grid configuration, and with the following set of
physics:</FONT></SPAN></DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial size=2>Radiation: Longwave
RRTM, Shortwave MM5-Dudhia</FONT></SPAN></DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial size=2>PBL: YSU (with
sfclay: Monin-Obukhov from MM5 MRF)</FONT></SPAN></DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial size=2>Surface: 5 layer MM5
LSM</FONT></SPAN></DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial size=2>Cumulus:
Kain-Fritsch</FONT></SPAN></DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial size=2>Microphysics:
WSM6</FONT></SPAN></DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=050511815-17062008><FONT face=Arial size=2>With this setup we
have experienced some problems related with Kain-Fritsch (we guess). After about
40-50 hours of simulation, error messages appear in the WRF output
textfiles:</FONT></SPAN></DIV>
<DIV><SPAN class=050511815-17062008><PRE><I>WOULD GO OFF TOP: KF_ETA_PARA I,J,DPTHMX,DPMIN</I></PRE><PRE><FONT face=Arial size=2>where NaNs appeared for DPTHMAX</FONT></PRE><PRE><FONT face=Arial size=2>We have tested with Betts-Miller-Janjic cumulus parameterization, and although no error messages appeared, wrfout files also have some NaNs inside.</FONT></PRE><PRE><FONT face=Arial size=2></FONT> </PRE><PRE><FONT face=Arial size=2>Do you have any suggestions? Thanks in advance!</FONT></PRE><PRE><FONT face=Arial size=2></FONT> </PRE><PRE><FONT face=Arial size=2>Eduardo Penabad<BR>MeteoGalicia</FONT></PRE><PRE><FONT face=Arial size=2></FONT> </PRE><PRE><EM></EM> </PRE></SPAN></DIV>
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