<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: arial,helvetica,sans-serif; font-size: 12pt; color: #000000'><style>p { margin: 0; }</style><div style="font-family: arial,helvetica,sans-serif; font-size: 12pt; color: #000000">Hi Mohsen,<div><br></div><div>Your expressions seem to be correct. If temperature is in K and winds are in m/s, temperature advection will be in K/s. You might want to plot it in K/day (multiply by 86400) to get "nicer" values on the order of 1-10 instead of those tiny (~1e-5) values.</div><div><br></div><div>Eric<br><br><hr id="zwchr"><b>From: </b>"Mohsen Soltani" <soltani.clima@gmail.com><br><b>To: </b>"GrADS Users Forum" <gradsusr@gradsusr.org><br><b>Sent: </b>Friday, May 24, 2013 2:29:35 PM<br><b>Subject: </b>[gradsusr] Temperature Advection<br><br><div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Dear Friends,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">
I have produced "Temperature Advection" using <span style="font-size:;font-family:monospace">cdiff</span> function, which is available at "GrADS Documentation Index":</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">
<a href="http://www.iges.org/grads/gadoc/gadocindex.html" style="font-family:arial" target="_blank">http://www.iges.org/grads/gadoc/gadocindex.html</a></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div>
<div class="gmail_default" style="font-family:arial,helvetica,sans-serif">The full command is like this:</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><dd style="color:;font-family:'Times New Roman';font-size:medium">
<code>define dtx = cdiff(t,x)</code></dd><dd style="color:;font-family:'Times New Roman';font-size:medium"><code>define dty = cdiff(t,y)</code></dd><dd style="color:;font-family:'Times New Roman';font-size:medium">
<code>define dx = cdiff(lon,x)*3.1416/180</code></dd><dd style="color:;font-family:'Times New Roman';font-size:medium"><code>define dy = cdiff(lat,y)*3.1416/180</code></dd><dd style="color:;font-family:'Times New Roman';font-size:medium">
<code>display -1*( (u*dtx)/(cos(lat*3.1416/180)*dx) + v*dty/dy )/6.37e6</code></dd><dd style="color:;font-family:'Times New Roman';font-size:medium"><code><br></code></dd></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">
where,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">the variable t is temperature, u and v are the U and V components of the wind, respectively.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">
<br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">In fact, <span style="font-family:arial">I am working on an advective cooling event (frost) over
Iran. The frost event was occurred as a result of an extra-ordinary extension
of the Polar Vortex toward the lower latitudes. </span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">The attached are the outputs that I made, which the first one indicates the start of the frost event, and the second one shows the end of the event over the country. I have to say that, they are in a very good agreement with the synoptic charts as well as outputs from HYSPLIT trajectory model.<span style="font-family:arial"><br>
</span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><p class="">Briefly speaking, is it really a temperature advection map? If
so, do you know what the unit of the temp advection is? And how it should be explained? </p><p class=""><br></p><p class="" style="">Thank you!</p></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">
Mohsen </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div><div dir="ltr"><span><span style="font-size:"></span></span><span><span dir="RTL" style="font-size:" lang="AR-SA"><span></span></span></span>--<div>
some are weather-wise some are otherwise!</div><div>--<br>Best Wishes, <br>(Mr.) Mohsen Soltani<br>Climatology Grad Student (M.Sc.),<br>Faculty of Geography, University of Tehran, Tehran, Iran<br>
Tel: (+98) 9119772934<br>e-mail: <a href="mailto:soltani.clima@gmail.com" target="_blank">soltani.clima@gmail.com</a><br></div></div></div>
</div>
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