[Wrf-users] Experiences with high-resolution WRF-ARW

[Gustafson, William I]

Eric,

My experience is that high vertical resolutions severely limit the time
step. For example, when running with 57 layers and the vertical resolution
set to about 35 m at the surface and dx=18, 6, and 2 km for the 3 nested
domains, I need timesteps of 30, 10, 3.33 sec, respectively. How far down
the timestep has to go will also be a function of the weather conditions in
the domain. If a frontal passage occurs, or deep convection, with strong
vertical velocities, a shorter timestep is required.

-Bill


On 2/27/08 1:01 PM, "Kemp, Eric M." <Eric.Kemp at ngc.com> wrote:

> 
> 
> Dear wrf-users:
> 
> My group is running WRF-ARW at high resolution (dx = 1 km) to simulate
> turbulence. 
> Recently we tried running at very high vertical resolution (dz ~= 12.5 m in
> the lowest
> 500 m of the domain), and encountered CFL errors with time steps as
> low as 1/8 of a second.  These runs used the 6th order diffusion
> option from Knievel et al (2007), along with real terrain (area around
> Albuquerque, NM) and physics (MYJ TKE, Noah land surface,
> RRTM/Dudhia radiation, and WSM5 microphysics).
> 
> Has anyone here run WRF at such fine resolution, and if so, what were
> your experiences with the time step?  The ARW documentation recommends
> 6 seconds for each kilometer of dx, ignoring the effect of vertical
> resolution. 
> Are there other settings that should be tuned?
> 
> -Eric
> 
> Eric M. Kemp
> Meteorologist
> Northrop Grumman Information Technology
> Intelligence Group (TASC)
> 4801 Stonecroft Boulevard
> Chantilly, VA 20151
> (703) 633-8300 x7078 (lab)
> (703) 633-8300 x8278 (office)
> (703) 449-3400       (fax)
> eric.kemp at ngc.com
> 
> 
> 
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--------------------------------------------------------------------
William I. Gustafson Jr.
Atmospheric Science and Global Change Division
Pacific Northwest National Laboratory
3200 Q Ave., MSIN K9-30
Richland, WA 99352
(509)372-6110

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