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

[Kemp, Eric M.]

I'd like to thank everyone who responded to my e-mail.  There were a lot of
suggestions made, and I thought it best to respond all at once.

To Nicole Molders:  I am using the WSM5 microphysics scheme with this domain.
I will check to see if heavy precipitation occurs.

To Sen Chiao:  I'm using 137 vertical levels.  The first 40 levels are in the
lowest 500 meters (dz ~ 12.5 meters); the next 12 km contain 73 vertical
levels, with dz varying from ~12.5 meters to ~304 meters using a hyperbolic
tangent stretching function.  The remaining 24 vertical levels fill the
domain up to 50 mb.  (These vertical resolutions assume the U.S. Standard
Atmosphere and a reference terrain height of 1631 meters.)

To Joe Galewsky:  I have also run WRF using dz = 50 m in the lowest 2 km,
then dz = 125 m for the next 12 km, then 500 m up to 50 mb.  Our time step
for this was 2 sec.  I made some attempts at increasing the horizontal
resolution to 0.5 km but experienced CFL errors.

To Chris Walker:   I am using the Mellor-Yamada-Janjic PBL scheme, but
with the ratio Km/Kh changed to use the equation from Kondo et al.
(J. Atmos. Sci., 1978) for stable conditions.  The 2D Smagorinsky
scheme is used for horizontal deformation.  I originally tried using the
3D TKE scheme (km_opt = 2), but this does not work with the land surface
model in WRF 2.2; we may try again with WRF 3.0.  I will investigate the
vertical diffusive CFL number.

To David Ovens:  I am using the 30 arcsec global terrain available with
WRF.  The GEOGRID.TBL.ARW file is standard, and specifies:
      * 1 smooth pass
      * the smth-desmth_special smoothing option
      * average_gcell(4.0)+four_pt+average_4pt interpolation
The documentation for the smoothing and interpolation options is poor, so
I need to look at the code to see what exactly is going on.

Thanks again!

-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



-----Original Message-----
From: wrf-users-bounces at ucar.edu on behalf of Kemp, Eric M.
Sent: Wed 2/27/2008 4:01 PM
To: wrf-users at ucar.edu
Subject: [Wrf-users] Experiences with high-resolution WRF-ARW
 

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



-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/wrf-users/attachments/20080228/a13138f5/attachment.html