ARWpost: interpolation in GrADS

Discussions related to the use of ARWPost

ARWpost: interpolation in GrADS

Postby Oscar van der Velde » Sun Dec 21, 2008 11:48 am

Hello,

I am looking for a solution for my problem. I use ARWpost to convert a Lambert-grid ARW run to GrADS readable output. This works, but I find that GrADS then interpolates everything at runtime. This slows down running my scripts so much that I consider it unworkable. I tried output at model levels, AGL and pressure levels and it makes no difference. Apparently, ARWpost itself does not do the interpolation to lat-lon that GrADS natively works at.
I think the solution is to work in lat-lon grids from the start, but I have not succeeded setting up the model correctly with the namelists, and I just read that ARWpost cannot currently handle lat-lon.

Another solution may be to use WPPv3 instead of ARWPost, but I never got this running correctly, and it cannot output files at fractional hours! (how else to make a nice simulated reflectivity loop?)
Do you know any other things I could try?

Oscar
Weather Photography | Sprites | Convective Weather Maps
http://www.lightningwizard.com
Oscar van der Velde
 
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Re: ARWpost: interpolation in GrADS

Postby leonard » Fri Jul 17, 2009 5:49 am

Hi Oscar,
I experienced the same issue. Do you have any solution?
leonard
 
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Re: ARWpost: interpolation in GrADS

Postby Oscar van der Velde » Fri Jul 17, 2009 8:20 am

No, since I basically tried to set it all up in my spare time, I gave up for the moment. I tried to run the model in lat/lon but couldn't get the configuration right with the domain selection tool and namelist file. But things may have improved with version 3.1.
Still, I wonder why ARWpost dumps output that still needs to be interpolated in real time by GrADS. If you have seen my Convective Weather Maps... it requires a lot of calculations in GrADS. It normally runs in about half an hour, but a WRF grid with fewer points requires ages because of the interpolation. I tried for example to calculate updraft helicity through a certain layer, which should be a simple calculation requiring a fraction of a second, but it takes something like 30 seconds.

Oscar
Weather Photography | Sprites | Convective Weather Maps
http://www.lightningwizard.com
Oscar van der Velde
 
Posts: 22
Joined: Tue Apr 15, 2008 8:38 pm
Location: Spain

Re: ARWpost: interpolation in GrADS

Postby thomas2 » Sun Jul 19, 2009 6:25 am

Hi Oscar,

In ARWpost 2.1 there is an undocumented option which I suggested to the WRF people. It is called "grads_low_res" and avoids interpolating into a "GrADS grid". It has to be set to true in the interp section.
Maybe that helps.

Thomas
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