[Wrf-users] Base-state potential temperature: 300 or 290 K?

[Eric Altshuler]

Dmitry, 


The base state value of 290 should not be changed. It's a parameter in WRF's hypothetical mean temperature profile. To get total potential temperature, it is equal to T + 300 (T is the perturbation potential temperature). Then use Poisson's equation to calculate temperature from potential temperature and pressure (pressure is also split into base and perturbation values). 


Best regards, 


Eric L. Altshuler 
Research Scientist 
Center for Ocean-Land-Atmosphere Studies 
4041 Powder Mill Road, Suite 302 
Calverton, MD 20705-3106 
USA 

E-mail: ela at cola.iges.org 
Phone: (301) 902-1257 
Fax: (301) 595-9793 

----- Original Message -----
From: "Dmitry Khvorostyanov" <dmitry.khvorostyanov at lmd.polytechnique.fr> 
To: wrf-users at ucar.edu 
Sent: Tuesday, June 11, 2013 1:28:22 PM 
Subject: [Wrf-users] Base-state potential temperature: 300 or 290 K? 

Dear WRF Users, 

I have a question concerning the value of the base-state potential 
temperature (the T00 variable in the WRF outputs). 

In the WRF Users' Guide, p. 5-79 (v 3.4) the total potential temperature 
is defined as T + 300. At the same time the namelist variable 
'base_temp' equals 290. 

Quickly looking through the code, it seems that the namelist value 290K 
is used for calculations, e.g., for the T2 field. 

However, in some parts of the code (apparently post-processing) the 
value of 300 is explicitly set. 

Also, trying to set 'base_temp' to 300 results in the eta levels 
definition error "dz (m) above fixed eta levels". 

Has anybody had to deal with this point? What value do you use to 
reconstruct the total potential temperature field? 

With best wishes, 
Dmitry 


-- 
Dmitry Khvorostyanov 
Laboratoire de Météorologie Dynamique IPSL 
Ecole Polytechnique 91128 Palaiseau Cedex 
France 


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