WRF NMM land mask and GrADS hires contours do not match

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nebojsa
Posts: 133
Joined: Sun Mar 21, 2010 3:40 pm

WRF NMM land mask and GrADS hires contours do not match

Post by nebojsa » Fri Feb 25, 2011 6:30 pm

On image is land mask of 20km resolution nested domain (60km resolution primar domain). Why is so big difference between hires and land/sea areas?
Image

And here the situation is worst:
Image

Main question si: which is relevant? Hires or land mask? What to do? To use real desired ponints coordinates or "move" them on the land?

meteoadriatic
Posts: 1543
Joined: Wed Aug 19, 2009 10:05 am

Re: land mask and hires

Post by meteoadriatic » Fri Feb 25, 2011 7:09 pm

nebojsa wrote:On image is land mask of 20km resolution nested domain (60km resolution primar domain). Why is so big difference between hires and land/sea areas?
That's because your parent domain is way too coarse (60km). It's how WRF-NMM nesting works; from NMM users guide:
WRF-NMM Guide wrote:When a nest is initialized, its topography is obtained from the static file created for that nest level by the WPS (see Chapter 3). Topography is the only field used from the static file. All other information for the nest is obtained from the lower-resolution parent domain. Land variables, such as land-sea mask, SST, soil temperature and moisture are obtained through a nearest-neighbor approach.
Link: http://www.dtcenter.org/wrf-nmm/users/d ... hap1-7.pdf

If you want much finer landmask, you must use much finer mother domain grid (for example, NAM uses 12km grid and that's really sweet spot for NMM).
nebojsa wrote:Main question si: which is relevant? Hires or land mask? What to do? To use real desired ponints coordinates or "move" them on the land?
Neither one is relevant. Landmask is incorrect due to explained above, and hires map in GrADS is also imprecise. However, in this example, hires map is much closer to real coast line.

nebojsa
Posts: 133
Joined: Sun Mar 21, 2010 3:40 pm

Re: land mask and hires

Post by nebojsa » Fri Feb 25, 2011 7:25 pm

Well, on the 32-bit machines, one can't use very fine resolution prime domain due to .grb file size limitation of 2GB.
Thanks on explanation!!

meteoadriatic
Posts: 1543
Joined: Wed Aug 19, 2009 10:05 am

Re: land mask and hires

Post by meteoadriatic » Fri Feb 25, 2011 9:08 pm

You don't have to use monolitic grib files (that is, do not concatenate all output gribs into one big grib). Look at post_grads.conf file near it's top. However, some scripting will probably be different if you disable monolitic files... you will have one grib, one ctl and one idx for every forecast time.

nebojsa
Posts: 133
Joined: Sun Mar 21, 2010 3:40 pm

Re: land mask and hires

Post by nebojsa » Sat Feb 26, 2011 1:56 pm

Thanks for advice, but at this point I do not feel able to change something radical in wrf philosophy. Perhaps once. But then I'll rather buy 64-bit machine :)
But, I've made a test and according to temperature, it seems that the wrf rather follows the land mask than hires. You may compare Scotland on above land mask and temperature fields on below image:
Image

Regards!!

apattant
Posts: 1
Joined: Wed May 30, 2012 6:38 pm

Re: WRF NMM land mask and GrADS hires contours do not match

Post by apattant » Wed May 30, 2012 6:42 pm

I am building a grid over Europe right now and am interested to know where did you get your landmask file from? Also, is it possible to plot topography shading over the landmask? I have tried this a few times and have not figured out a way to make it work yet. Thanks in advance.

-Andre

meteoadriatic
Posts: 1543
Joined: Wed Aug 19, 2009 10:05 am

Re: WRF NMM land mask and GrADS hires contours do not match

Post by meteoadriatic » Wed May 30, 2012 9:11 pm

That is landmask from model output (from model grib files). Yes, model topografy is also there inside gribs.

What postprocessing software do you use?

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