Removing topography

Any problems/questions that might not fall into the other topics in this category.

Re: Removing topography

Postby camelstation » Sat Jan 07, 2012 11:08 pm

PBLer wrote:That *might* be all you need, but I usually modify the slope fields as well as the HGT_U and HGT_V fields.

HGT_M:description = "Topography height" ;
SLPX:description = "df/dx" ;
SLPY:description = "df/dy" ;
HGT_U:description = "Topography height"
HGT_V:description = "Topography height" ;

I contacted WRF Help about this and they said that the model only uses HGT_M.

i.e., if you want to alter the topography, you only have to alter HGT_M as the model does not use HGT_U, HGT_V, SLPX or SLPY.

I have confirmed this with simulations.
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Joined: Thu Jul 21, 2011 8:42 pm

Re: Removing topography

Postby fard792 » Mon Sep 17, 2012 1:42 am

Hi. I'm trying to remove topographic features too , but i want to know that only "HGT_M" must be change or others such as"HGT_U" , "HGT_V" should be change
please describe me how can i change topography data
Please inform me some links or example
Highly appreciated.
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Joined: Wed Apr 15, 2009 3:55 am

Re: Removing topography

Postby Thunder Road » Sat Aug 30, 2014 11:25 am

Apologies for bumping a dormant thread.

I'm trying to modify the coastline of Lake Michigan to see if smoothing it out (removing a few bowl-shaped areas uplake) affects vortex generation in a specific type of lake-effect.

Is this something that's possible? From reading the thread, it sounds like I can set HGT_M to 0 in geo_em for the desired grid points. But will this have the same effect as essentially expanding the area of Lake Michigan? Or would it just create a region of 0 m elevation adjacent to the lake? (Obviously the lake/land boundary, and associated temperature gradient, are critical for lake-effect production.)

I've also seen LANDMASK mentioned, but I don't know anything about that.

I'm rather new to WRFing, but hopefully someone can help!

Thunder Road
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Joined: Sat Aug 30, 2014 11:15 am

Re: Removing topography

Postby jbasconcillo » Mon Sep 16, 2019 3:14 am

I am reducing elevation to 1 meters above sea level. I only want to remove orography not the entire land.

I edited geo_em.d0* with the following values:

HGT_M = 1
LU_INDEX = 19 (barren; ... F_Tutorial)
ALBEDO12M=0.17 (bare soil)

My wrfout_d0* of P and T still looks like there is still semblance of elevation.

In namelist.input, I changed:


What did I miss? Can you help me?


The initial time (time=0) still retains the elevation profile. Is there something I can do?

In the wrfinput_d01, the TSK among other variables still retains the elevation when I open it in ncview.
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Joined: Thu May 16, 2019 8:56 am


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