[Wrf-users] properly removing topography from a restart simulation?

[Marcella, Marc]

Thanks Surya,
I simply used NCL to zero out the corresponding fields and re-write the geogrid.nc.  Everything looks like it is zeroed out except the resulting fields from topography  (ie surface pressure, t2,etc.) they all still reflect a region with topography for some reason (in both the input and output files.) Not sure if Im missing certain variables that also need to be zeroed out or something else.

-----Original Message-----
From: Surya Ramaswamy [mailto:Surya.Ramaswamy at erm.com] 
Sent: Wednesday, July 29, 2015 1:40 PM
To: Marcella, Marc; wrf-users at ucar.edu
Subject: RE: properly removing topography from a restart simulation?

Hi Marc - I'm not sure how you changed the topography variables. Last time, when I need to change the topo variables including surface characteristics and elevation under /geo_data/geog/, I used the java utility from http://www.wrfems.info/dmbrown1/

This is a great tool and seems to work fine for me. You can also easily validate the resulting topo. If you decide to try this route, I'm interested to see if there is any difference in the geo*.nc file created using this tool and yours.

Good Luck

Surya

-----Original Message-----
From: wrf-users-bounces at ucar.edu [mailto:wrf-users-bounces at ucar.edu] On Behalf Of Marcella, Marc
Sent: Wednesday, July 29, 2015 9:46 AM
To: wrf-users at ucar.edu
Subject: [Wrf-users] properly removing topography from a restart simulation?

Hi wrfusers,

I am trying to remove topography over Taiwan in a WRF simulation where I restart from a prior run to simulate the effects on a typhoon traversing the region.  The procedure I follow is to remove the topography (HGT_M, VAR_SSO, and SLOPECAT variables) in geogrid, re-run metgrid.exe, then re-run real.exe.  I checked the geo.nc, met.nc files, and the real input files---all show the topography variables over the region as zeroed out.  I then am sure to remove the topography from the wrfrst.nc file that the simulation is restarting from.

When I run the model however, the results do look slightly different than a simulation with topography but not significant given the drastic change (from having topo go from 3km to 0km). Similarly, the results still show a barrier of sorts when the wind/rainfield comes ashore.  When I check the restart files created after the fact, I see that the topography is still 0 but the surface pressure over the island appears as if mountains are there as it is very low (~800mb) as is the sfc pressure in the met_em.nc files.  My question is, am I properly removing the topography? Or are there other variables that also must be zeroed out to mimic a 0km island?  And, is there some other definitive check I can perform to ensure that this simulation is actually not seeing the topography?

Any help would be greatly appreciated.

Thanks,
Marc
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