Re: Isentropic surface plots with WRF output

Relating to my previous post - Gene Petrescu (Missoula WFO SOO)
noted that our theta levels weren't always increasing with height, and
in such places the int2p() function failed and produced the 1+e36 values
(which I later found were "fill" values). I don't pretend to fully understand
this, but I wanted to offer this insight of Gene's.

For our purposes, Gene suggested a quick hack that would essentially
go through our THETA array and insure that THETA will never decrease
with height. I don't know that it's a good "general" solution, but it does
result in our theta surface plots being "full" now.

On Thu, May 1, 2008 at 9:18 PM, Don Morton <donaldjmorton_at_gmail.com> wrote:
> Hi, the semester is just about done, so I'm back...
>
> We're trying to produce some plots of pressure, humidity
> and wind on isentropic surfaces from our WRF model output.
>
> I found an NCL example at:
>
> <http://www.ncl.ucar.edu/Applications/isent.shtml>
>
> and have tried to apply the methods to our own
> situation. I've simplified the script as much as I could
> for this problem statement, and it's available at
>
> <http://weather.arsc.edu/Miscellaneous/NCL/IsentropicSurface/wrfIsentropic-P.ncl>
>
> The input data, "wrfoutd02.nc" is also in that directory
>
> <http://weather.arsc.edu/Miscellaneous/NCL/IsentropicSurface/wrfoutd02.nc>
>
> The output image produced by this script/data is at
>
> <http://weather.arsc.edu/Miscellaneous/NCL/IsentropicSurface/A.jpg>
>
> The problem is that the plot is full of "no" values. This is
> understandable where the theta surface might run into the
> terrain, but not over the ocean. At the very least, if our theta
> surface was starting to collide with the ocean surface, we would
> expect to see pressures of around 1000mb in those areas.
> But, as you can see, we just have a lot of "missing" data.
>
> In my script, I've printed out ALL the pressure values on the theta
> surface (pf_xlvl), and there are lots of values of 1+e36, which strikes
> me as some sort of numerical issue. Just for the heck of it, at one of
> those points (9, 370), I've printed out the column of values for theta
> and pressure, and those values look good. This debugging output
> (2+ Mbytes) is available at
>
> <http://weather.arsc.edu/Miscellaneous/NCL/IsentropicSurface/t.out>
>
>
> One of the meteorologists who's looked at the output feels that the
> areas that "are" plotted look reasonable, but we can't explain all those
> missing values.
>
> I have to admit that I'm kind of out of my league on this one. I've had
> some thoughts that the NCL example referenced above might assume
> data on pressure levels, whilst the stuff I'm working with is terrain-following,
> but if it's really just a simple interpolation function, maybe that shouldn't
> matter?
>
> I feel like I'm just "black-boxing" my use of int2p(), so could easily be
> missing something very fundamental...
>
> Thanks for listening!
>
> Don Morton
>
> --
> University of Montana
> http://www.cs.umt.edu/~morton/
> Arctic Region Supercomputing Center
> http://weather.arsc.edu/
>

-- 
University of Montana
http://www.cs.umt.edu/~morton/
Arctic Region Supercomputing Center
http://weather.arsc.edu/
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