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

[Jim Dudhia]

My opinion is it should go with the finest domain resolution (1 minute  
per km dx),
but there is not often much need to go below 5 minutes. All domains  
should
use the same value, but it is not a big problem if they don't,
Jimy

On Apr 9, 2010, at 3:26 PM, Eric Altshuler wrote:

> 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
> USA
>
> 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.
>
>
> Regards,
> 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,
> Agnes
>
> -- 
> Dr. A'gnes Mika
> Advisor, Meteorology and Air Quality
>
> Tel: +31 (0)527-242299
> Fax: +31 (0)527-242016
> Web: www.bmtargoss.com
>
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