[gradsusr] Lifted Index Formula

[Jeff Duda]

You've confused the different uses of scripting functions vs. Grads prompt
functions.  You can only display a variable that you have defined using the
'define ...' command (note the use of the quotes signaling that it was
defined as if you typed it in at the Grads prompt).  Your use of variable =
satvap(...) with satvap being a script function only is causing Grads to
assume variable is a script variable only, not one that can be displayed.
The reason you get the other error when you put the other line in quotes is
because math_exp is strictly a script version of the exp function that you
would use in the Grads command prompt.  Thus, you would want to change that
line to

'es = 6.112*exp(17.67*temp/(temp+243.5))'

in order to display es or define any other variables that would depend on
it.

Jeff Duda

On Thu, Mar 1, 2012 at 7:06 AM, Mike Manning <michael at bsch.au.com> wrote:

> Hi everyone,
>
> I'm using data from the FNMOC model and am trying to make a function
> that calculates Lifted Index.  I'm using bits of the code from the
> plotskew.gs code.  So far I've got the temperature (celsius) and
> dewpoint (celsius) worked out for each level.  Now I'm calculating the
> parcel details.. I've pulled some of the functions and have just been
> testing to make sure I'm on the right track.  If I have this code for
> example:
>
> 'c'
> 'reinit'
> 'open gfs.00z.ctl'
> 'set t 7'
> 'set lon 135 155'
> 'set lat -31 -10'
>
> 'set lev 1000'
> 't1000mb = TMPprs-273.14'
> 'define dp1000mb =
>
> t1000mb-((14.55+0.114*t1000mb)*(1-0.01*RHprs)+pow((2.5+0.007*t1000mb)*(1-0.01*RHprs),3)+(15.9+0.117*t1000mb)*pow((1-0.01*RHprs),14))'
>
> variable = satvap2(t1000mb)
>
> 'd variable'
>
> function satvap2(temp)
>
> *---------------------------------------------------------------
> * Given temp in Celsius, returns saturation vapor pressure in mb
> *---------------------------------------------------------------
>
> es=6.112*math_exp(17.67*temp/(temp+243.5))
>
> return(es)
> 'quit'
>
>
>
> it complains about an error? If I put the code in the satvap2 function
> in single quotes it then says "math_exp" is not a variable or function"?
> I'm a little lost on how to fix this one up if it's possible.
>
> Cheers, Mike
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>



-- 
Jeff Duda
Graduate research assistant
University of Oklahoma School of Meteorology
Center for Analysis and Prediction of Storms
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