Re: Offset terrain in WRF Polar Stereographic

From: Don Morton <Don.Morton_at_nyahnyahspammersnyahnyah>
Date: Wed Feb 17 2010 - 11:29:22 MST

Thank you, Mary.

Yes, that's the approach I've been using (you're actually the one who
pointed me to it several years ago - you taught me everything I know!!), and
that "skew" has always been an issue, and people comment on it, BUT, it puts
the data in the right place. You can see we even use your "Mary Haley Shove
Those Darned Gridpoints Where They Belong" method in our daily runs - the
right hand side is skewed just a little.

http://weather.arsc.edu/ForecastProducts/AKTrial2/webImages/html/forecast-d02.php

So, I guess I'm wondering if this is something that the WRF NCL routines
should be expected to handle. I don't know if it matters or not, but (for
wrfhelp's benefit) here are the namelist.wps entries used to create the
domain. If anyone wants to look at it, I happen to have an 81km (and 27km)
resolution wrfout file of the same region, so those would be smaller files
(one and two orders of magnitude, respectively).

&geogrid
 parent_id = 1,
 parent_grid_ratio = 1,
 i_parent_start = 1,
 j_parent_start = 1,
 e_we = 675,
 e_sn = 675,
 geog_data_res = '2m','2m',
 dx = 9000,
 dy = 9000,
 map_proj = 'polar',
 ref_lat = 64.85,
 ref_lon = -147.85,
 truelat1 = 64.85,
 stand_lon = -147.85,
 geog_data_path = '/datadir/morton/WRF/geog'
/

On Tue, Feb 16, 2010 at 2:37 PM, Mary Haley <haley@ucar.edu> wrote:

> Don,
>
> I converted your wrf_xxxx to use gsn_xxxx functions, so that I could use
> the XLAT and XLONG values on the file to do the transformation, instead
> of depending on the map projection to be exactly right.
>
> I did use the same map parameters that I believe wrf_xxxx is trying to use.
>
> As you can see, the contours now fall within the borders much better, but
> it also looks like the rotation is skewed a little. I think maybe either the
> wrf_map_overlays function isn't doing the right thing, or else the map
> parameters on your file are not correct. My guess is that mpCenterLonF or
> mpCenterLatF may be incorrect, or one of the Corners resources is incorrect.
>
> Perhaps wrfhelp has some information here...
>
> --Mary
>
>
> On Feb 16, 2010, at 12:04 PM, Don Morton wrote:
>
> Hi,
>
> I thought this problem had been resolved ages ago, but maybe only for
> Lambert projections.
>
> I'm using NCL 5.1.1 on WRF v3.1.1 netCDF output with polar stereographic
> projection, and I'm running into the same old terrain-offset issues that
> some of us have mentioned over the past several years.
>
> Am I correct in my expectations that the WRF NCL mapping routines "should"
> handle this these days? Or, am I possibly missing something key? I can go
> back and handle this the old way, using the standard NCL plotting functions
> I once used, with the following sorts of resource settings
>
> res@gsnAddCyclic = False ; Regional data, not cyclic
>
> res@tfDoNDCOverlay = False ; Set True for native
> projection
>
> ; Specify map boundaries
> res@mpLimitMode = "Corners" ; Use the corners limit
> mode
>
>
> and not using all those convenient WRF functions, but now I'm wondering...
>
>
> My resulting image is at
>
> <http://weather.arsc.edu/Miscellaneous/NCLWoes/Hgt.png>
>
> With a simplified script available at
>
> <http://weather.arsc.edu/Miscellaneous/NCLWoes/Hgt.ncl>
>
> and the wrfout file (870 Mbytes) available at
>
> <
> http://weather.arsc.edu/Miscellaneous/NCLWoes/wrfout_d01_2009-12-20_00:00:00
> >
>
>
> --
> Arctic Region Supercomputing Center
> http://www.arsc.edu/~morton/ <http://www.arsc.edu/%7Emorton/>
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>
>
>

-- 
Arctic Region Supercomputing Center
http://www.arsc.edu/~morton/
Received on Wed Feb 17 11:29:40 2010

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