[Wrf-users] Radiation timestep - what to use?

Eric Altshuler ela at cola.iges.org
Fri Apr 9 15:26:41 MDT 2010

Dear wrf users,

I have asked this same question several times (over the course of several years) and never gotten a definitive answer. Even among the WRF developers, opinions differ. In one case, I had the same nesting configuration (3 domains, 27/9/3km resolution). I got several responses but they did not agree. Some would recommend to set radt = 27; others would recommend using radt = 3. I chose the middle ground by setting radt = 9, but it would be nice to settle this question once and for all.

Best regards,

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

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

----- Original Message -----
From: "Abdullah Kahraman" <havadurumu at gmail.com>
To: wrf-users at ucar.edu
Sent: Friday, April 9, 2010 4:27:41 PM
Subject: Re: [Wrf-users] Radiation timestep - what to use?

Hello Agnes, 

This question was asked before, maybe you can find out in the archive. You are supposed to use 27 km for all domains. 

Abdullah KAHRAMAN 
M.Sc. Meteorological Engineer 
Turkish State Meteorological Service 
Ph.D. Student 
Istanbul Technical University, Atmospheric Sciences Program 

On Fri, Apr 9, 2010 at 11:22, Agnes Mika < agnes.mika at bmtargoss.com > wrote: 

Dear WRF help and WRF users, 

I am confused about what value I should use for the radiation 
timestep. The recommendation in the manual is 1 minute per km of dx 
and to use the same value for all nests. 

Should I use the radt valid for the coarsest or the finest nest for 
all nests? 

E.g., I am using nests with 27, 9, and 3 km resolution. Should radt 
be set to 27 for all nests or to 3? 

Thank you in advance, 

Dr. A'gnes Mika 
Advisor, Meteorology and Air Quality 

Tel: +31 (0)527-242299 
Fax: +31 (0)527-242016 
Web: www.bmtargoss.com 

P.O. Box 61, 8325 ZH Vollenhove 
Voorsterweg 28, 8316 PT Marknesse 
The Netherlands 

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