Overlay different resolution grids using OpenGrADS re()

[Mike Johnson]

Arlindo - I hadn't thought about UNDEF...I checked that with "set gxout stat" as you suggested and discovered that undefined data were tagged with 1e+36, after putting that in my ctl file - it worked.

I had assumed that there was no undefined data...I'm still not sure why there would be in this data set.  Anyway...the -9999.0 that was in there previously, I just made up to satisfy GrADS complaint to list it.


thanks for the tip

Mike Johnson


----- Original Message -----
From: Arlindo da Silva <dasilva at ALUM.MIT.EDU>
Date: Sunday, June 22, 2008 9:04 am
Subject: Re: Overlay different resolution grids using OpenGrADS re()
To: GRADSUSR at LIST.CINECA.IT


> On Fri, Jun 20, 2008 at 9:32 PM, Mike Johnson <mike.w.johnson at noaa.gov>
>  wrote:
>
>  > Users, Can anyone help with what I suspect is either a regrid problem
>  > (using re.gex) - or - in the methodology I'm using for output
> fwrite - or -
>  > an issue with my understanding of how options yrev works.
>
>
>  This shouldn't be an issue in this case. Usually, when you misuse
> yrev you
>  end up with an upside down plot, something easy to diagnose.
>
>
>  > I am attempting
>  > to regrid a subdomain of a large regional netcdf topo file
>  > (US_Rockies_GLOBE_30sec_topo.nc resolution - 30 Sec resolution) and
> write
>  > that regridded subdomain to a binary file (Idaho.dat) which I then
> want to
>  > overlay with high resolution surface wind field from CALMET (0.25km
>  > resolution).
>  >
>  > My basic procedure is to (1) convert grid spacing for control files
> and re
>  > () to DeltaX and DeltaY in degrees; (2) select a subdomain of the large
>  > NetCDF TOPO file (US_Rockies_GLOBE_30sec_topo.nc) which has Y dims
> written
>  > from north-to-south and (3) to regrid this smaller domain using
> re() in
>  > order to match domain size and dimensions of CALMET surface wind
> field; and
>  > (4) write a binary file (Idaho.dat) which I'm hoping to overlay
> with the
>  > CALMET wind data (and future runs of this model over the same domain).
>  >
>  > I am able to open large domain TOPO file (US_Rockies_GLOBE_30sec_topo.nc),
>  > regrid to higher resolution and plot subdomain. However...after writing
>  > this re-gridded subdomain file to binary output (Idaho.dat), when I
> try to
>  > plot it using (Idaho.ctl) the file appears to be garbage with GrADS
>  > echoing "Contouring: 1e+36 to 9e+36" whereas in reality values
> should be
>  > something like "1000 to 2800".
>  >
>
>  Hmm... In your ctl you have
>
>  UNDEF -9999.0
>
>  are you sure of that? Do you have any UNDEF in your dataset? Make
> sure re()
>  is not adding undef at the borders. Here is a couple of things you
> could do
>  to further diagnose your problem:
>
>  1) Specify the clevs when contouring your data:
>
>  ga-> set clevs 1000 1500 2000 2500 3000
>  ga-> d tpo
>
>  2) Examine the min/max of your data:
>
>  ga-> set gxout stat
>  ga-> d tpo
>
>     Arlindo
>
>
>
>
>  --
>  Arlindo da Silva
>  dasilva at alum.mit.edu