Re: Re: Isentropic surface plots with WRF output

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Thu, 01 May 2008 17:31:32 -0600

Just fyi:
http://www.ncl.ucar.edu/Document/Functions/Built-in/int2p.shtml

/pin/

An array of any dimensionality containing input pressure levels. If
multi-dimensional,
the level dimension must be in the rightmost position
and the values must be monotonically increasing or decreasing.

If the "pin" fold .... the interpolation returnd _FillValue.

//
Don Morton wrote:
> 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/
>>
>>
>
>
>
>

-- 
======================================================
Dennis J. Shea                  tel: 303-497-1361    |
P.O. Box 3000                   fax: 303-497-1333    |
Climate Analysis Section                             |
Climate & Global Dynamics Div.                       |
National Center for Atmospheric Research             |
Boulder, CO  80307                                   |
USA                        email: shea 'at' ucar.edu |
======================================================
_______________________________________________
ncl-talk mailing list
ncl-talk_at_ucar.edu
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Thu May 01 2008 - 17:31:32 MDT

This archive was generated by hypermail 2.2.0 : Mon May 05 2008 - 14:52:49 MDT