[gradsusr] Temperature Advection

[Eric Altshuler]

display -86400*( (u*dtx)/(cos(lat*3.1416/180)*dx) + v*dty/dy )/6.37e6 


----- Original Message -----
From: "Mohsen Soltani" <soltani.clima at gmail.com> 
To: "GrADS Users Forum" <gradsusr at gradsusr.org> 
Sent: Saturday, May 25, 2013 1:24:19 AM 
Subject: Re: [gradsusr] Temperature Advection 



Hello Eric, 


Thank you very much for your nice suggestion. Yes, it would be much better, if I plot it in K/day. But, where exactly I should put this (86400) in the following function? 


define dtx = cdiff(t,x) define dty = cdiff(t,y) define dx = cdiff(lon,x)*3.1416/180 define dy = cdiff(lat,y)*3.1416/180 display -1*( (u*dtx)/(cos(lat*3.1416/180)*dx) + v*dty/dy )/6.37e6 




Thank you! 
Mohsen 





-- 
some are weather-wise some are otherwise! 
-- 
Best Wishes, 
(Mr.) Mohsen Soltani 
Climatology Grad Student (M.Sc.), 
Faculty of Geography, University of Tehran, Tehran, Iran 
Tel: (+98) 9119772934 
e-mail: soltani.clima at gmail.com 



On Fri, May 24, 2013 at 12:48 PM, Eric Altshuler < ela at cola.iges.org > wrote: 





Hi Mohsen, 


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. 


Eric 


From: "Mohsen Soltani" < soltani.clima at gmail.com > 
To: "GrADS Users Forum" < gradsusr at gradsusr.org > 
Sent: Friday, May 24, 2013 2:29:35 PM 
Subject: [gradsusr] Temperature Advection 





Dear Friends, 


I have produced "Temperature Advection" using cdiff function, which is available at "GrADS Documentation Index": 
http://www.iges.org/grads/gadoc/gadocindex.html 


The full command is like this: 
define dtx = cdiff(t,x) define dty = cdiff(t,y) define dx = cdiff(lon,x)*3.1416/180 define dy = cdiff(lat,y)*3.1416/180 display -1*( (u*dtx)/(cos(lat*3.1416/180)*dx) + v*dty/dy )/6.37e6 

where, 
the variable t is temperature, u and v are the U and V components of the wind, respectively. 


In fact, 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. 
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. 



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? 




Thank you! 
Mohsen 



-- 
some are weather-wise some are otherwise! 
-- 
Best Wishes, 
(Mr.) Mohsen Soltani 
Climatology Grad Student (M.Sc.), 
Faculty of Geography, University of Tehran, Tehran, Iran 
Tel: (+98) 9119772934 
e-mail: soltani.clima at gmail.com 

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