20050415: IDV - Combined model Temperatures

>From: Alan Klein <address@hidden>
>Organization: St. Cloud  State
>Keywords: 200504150415.j3F4Fav2004491 IDV formula

Hi Alan-

>> How are you doing this?  Do you have a Jython program for this?
>> If you can send me the formula, I can try to recreate this.
>                               I am using a super basic formula.
>                       Here is the exported formula: (G = GFS Temperature at F
> ixed Level; N  
>= NGM Temperature at Fixed Level)
>                       <derived_parameters>
>                               <derived id="Temperature at Fixed Level" descri
> ption="TEMP"  
>formula="(G+N)/2" isenduser="true" isdefault="false">
>                                <categories/>
>                               <operands/>
>                               </derived>
>                       </derived_parameters>
>
>               **NOTE: I have successfully used this equation to plot precipit
> ation  
>(Using G=GFS Total Precipitation at Surface of the Earth;
>                               N=NGM Total Precipitation at Surface of the Ear
> th).

Okay, there are a couple of problems here.  First, you are trying
to average a 3D grid (NGM) with a 2D grid (GFS) which you probably 
shouldn't try.  In some cases it will work, but in general, it's
like mixing apples and oranges.  Because the result garbage, you are
getting the errors when the IDV tries to calculate the max and
min.  I'll change the way that is handled for a future release.

I did get this to work if I tried to average the Eta and GFS, but
I'd say that's amazing that it worked.

The second problem is that the NGM has different fixed height levels
than the other models.  Eta and GFS have 2 meter temps whereas the
NGM data has different levels.  This may be a decoder problem
(because the levels are 1829,2743,3658) and I'll look into it.

> Inquiry: This is the other error that I get if I try to combine the NAM(ETA),
>NGM and GFS models.(Temperature at a fixed height)
> 
> This equation looks like:
> (E+N+G)/3
> 
> An error has occurred:
> ControlDescriptor.Creating display
> org.python.core.PySyntaxError
> 
> ******************
> Stack trace:
> Traceback (innermost last):
>   (no code object) at line 0
> SyntaxError: ('invalid syntax', ('<string>', 1, 1, ''))

Actually, this is a red herring of an error.  The real problem 
is that of mixing 2 and 3D grids.

Since the NGM does not have the same levels as the other models,
I'm not sure you can do what you are trying.  

Don Murray
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Date:    Fri, 15 Apr 2005 10:06:47 CDT
From:    <address@hidden>
Subject: RE: 20050415: IDV - Combined model Temperatures 

Thanks for your help. I thought that this (2d vs 3d) could be the problem, but 
I wanted to make sure that it wasn't just my computer trying to trick me.What i
s super wierd is that I actually got it to work one time, but of course it neve
r worked again.

Thanks again for looking into this.

--Alan Klein