<html><head><base href="x-msg://403/"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">All,<div>In cases of stronger winds the averaging time can be considered equivalent</div><div>to the advective time-scale across a grid box when looking at the U10 and V10.</div><div>So for a 4 km hurricane run with 40 m/s, it would be 4000/40=100 seconds</div><div>which may be comparable with 1-minute averages,</div><div>Jimy</div><div><br><div><div>On Jan 27, 2010, at 8:12 AM, Ligia Bernardet wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Josh and Juan,<div><br></div><div>I ran into this issue while trying to compare 10-m model wind forecasts against hurricane maximum wind reports, which are also an average over a few minutes. There was no good solution. </div><div><br></div><div>Having WRF output time series of variables at a grid point or time series of statistical quantities (such as maximum winds) has been a standing request to developers, and may be addressed at some point. </div><div><br></div><div>I have talked to several hurricane modelers who, for research purposes, output the model winds every time step to look at how much it varies. Different authors got to different conclusions. Some modelers noted that their model winds fluctuate a lot (and therefore averaging is really necessary before comparing to obs), other noted that their winds are pretty steady (and therefore direct comparison to observations is not a problem).</div><div><br></div><div>So, I think this is an outstanding issue. If others have experience with this, I would also like to know more.</div><div><br></div><div>Ligia</div><div><br></div><div><br></div><div><br></div><div><br><div><div>On Jan 26, 2010, at 5:06 PM, Hacker, Joshua (Josh) (CIV) wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div lang="EN-US" link="blue" vlink="purple"><div class="Section1"><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; ">Apologies to those who know this better than I do, but this is an interesting question…<o:p></o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; "><o:p> </o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; ">Unless you do something fancy, the WRF outputs instantaneous grid-point values, regardless of your output interval. Those values are filtered non-trivially by some function of implicit and explicit diffusion in the model (think physics, damping, time and space discretization, etc). Therefore there is no one answer to your question. <o:p></o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; "><o:p> </o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; ">In practice (I believe) most people just compare directly to 10-min averaged wind obs (WMO standard), or 2-min averaged wind obs (USA) but in my opinion 2 minutes is usually too short to be fair.<o:p></o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; "><o:p> </o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; ">One approach to getting at the averaging in the model is through data assimilation and statistical consideration of observation error levels when the error may be dominated by representativeness error (difference between scales represented in obs and model). Others have looked in spectral space to get an idea of the averaging scales.<o:p></o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; "><o:p> </o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; ">The other thing that you might consider, if you have the data to do it, is to compare WRF forecasts with obs averaged over many different time lengths (or alternatively band-pass filtered). Then you can get a more complete picture of what time scales it can or cannot predict with skill, and decide whether it is doing what you hope.<o:p></o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; "><o:p> </o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; ">That said, I’d be interested in hearing any other comments from the community and especially our verification gurus – is there any “conventional” wisdom or rules of thumb that folks are using or that have recently shown promise, empirically? Have I missed something?<o:p></o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; "><o:p> </o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; ">Sorry that there is no simple answer.<o:p></o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; "><o:p> </o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; ">Josh<o:p></o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy; "><o:p> </o:p></span></font></div><div><div class="MsoNormal" align="center" style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; text-align: center; "><font size="3" face="Times New Roman"><span style="font-size: 12pt; "><hr size="2" width="100%" align="center" tabindex="-1"></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><b><font size="2" face="Tahoma"><span style="font-size: 10pt; font-family: Tahoma; font-weight: bold; ">From:</span></font></b><font size="2" face="Tahoma"><span style="font-size: 10pt; font-family: Tahoma; "><span class="Apple-converted-space"> </span><a href="mailto:wrf-users-bounces@ucar.edu" style="color: blue; text-decoration: underline; ">wrf-users-bounces@ucar.edu</a><span class="Apple-converted-space"> </span>[<a href="mailto:wrf-users-bounces@ucar.edu">mailto:wrf-users-bounces@ucar.edu</a>]<span class="Apple-converted-space"> </span><b><span style="font-weight: bold; ">On Behalf Of<span class="Apple-converted-space"> </span></span></b>Juan Gonzalez<br><b><span style="font-weight: bold; ">Sent:</span></b><span class="Apple-converted-space"> </span>Tuesday, January 26, 2010 12:33 PM<br><b><span style="font-weight: bold; ">To:</span></b><span class="Apple-converted-space"> </span><a href="mailto:wrf-users@ucar.edu" style="color: blue; text-decoration: underline; ">wrf-users@ucar.edu</a><br><b><span style="font-weight: bold; ">Subject:</span></b><span class="Apple-converted-space"> </span>[Wrf-users] Comparing U,V 10 meters to observations</span></font><o:p></o:p></div></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="3" face="Times New Roman"><span style="font-size: 12pt; "><o:p> </o:p></span></font></div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="3" face="Times New Roman"><span style="font-size: 12pt; ">Hi everyone,<o:p></o:p></span></font></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="3" face="Times New Roman"><span style="font-size: 12pt; "><o:p> </o:p></span></font></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="3" face="Times New Roman"><span style="font-size: 12pt; ">I am interested on validating the WRF 10m wind forecast with observational data. I would like to know what is the corresponding average scale for the WRF 10m winds, that is, do the correspond to 1-minute, 10-minute average winds or what kind of average, if any?<o:p></o:p></span></font></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="3" face="Times New Roman"><span style="font-size: 12pt; "><o:p> </o:p></span></font></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="3" face="Times New Roman"><span style="font-size: 12pt; ">My WRF configuration outputs wind every 3 hours.<o:p></o:p></span></font></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="3" face="Times New Roman"><span style="font-size: 12pt; "><o:p> </o:p></span></font></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="3" face="Times New Roman"><span style="font-size: 12pt; ">Thanks for your help, <o:p></o:p></span></font></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman'; "><font size="3" face="Times New Roman"><span style="font-size: 12pt; ">Juan Gonzalez <br clear="all"><br>--<span class="Apple-converted-space"> </span><br>Juan O. Gonzalez<br>Research Assistant - Caribbean Integrated Coastal Ocean Observing System<br><br>Graduate Student - Physical Oceanography<br>Marine Sciences Department<br>University of Puerto Rico - Mayaguez Campus<o:p></o:p></span></font></div></div></div>_______________________________________________<br>Wrf-users mailing list<br><a href="mailto:Wrf-users@ucar.edu" style="color: blue; text-decoration: underline; ">Wrf-users@ucar.edu</a><br><a href="http://mailman.ucar.edu/mailman/listinfo/wrf-users" style="color: blue; text-decoration: underline; ">http://mailman.ucar.edu/mailman/listinfo/wrf-users</a><br></div></span></blockquote></div><br></div></div>_______________________________________________<br>Wrf-users mailing list<br><a href="mailto:Wrf-users@ucar.edu">Wrf-users@ucar.edu</a><br>http://mailman.ucar.edu/mailman/listinfo/wrf-users<br></blockquote></div><br></div></body></html>