[gradsusr] pow() function with negative exponent - unusual behavior

Jeff Duda jeffduda319 at gmail.com
Thu Jan 9 14:12:31 EST 2020

I do not know the issue with using a negative number in the pow() function,
but try using the assumed definition of a negative power as 1/term:

'd 0.1*(1 / pow(prate,0.54))'

Does that give you the expected behavior?


On Thu, Jan 9, 2020 at 11:50 AM L.B. <bcbass2989 at gmail.com> wrote:

> Hello,
> I am having an issue with the pow() function using a negative exponent. It
> is displaying a constant field where it should be a variable field. I have
> attached the grib file as well as the ctl file and all relevant equations
> are below:
> The grib file contains the precipitation rate. I am trying to create a
> field which uses the precip rate as follows:
> *'define prate = (pratesfc/25.4)*3600'   **Converting the precip rate
> field to in/hr*
> Plotting this yields a varying precip rate field in inches/hour.
> Next, I want to apply the following equation to the prate field:
> *'d 0.1*pow(prate,-0.54)'*
> The issue is that it creates a constant field with a value of 0.0563103
> when it should still be a varying field. Is this a bug with pow() function,
> or is something else going on here?
> *-------*
> William LaForce IV
> Meteorologist
> _______________________________________________
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> gradsusr at gradsusr.org
> http://gradsusr.org/mailman/listinfo/gradsusr

Jeff Duda, Research Scientist
University of Colorado Boulder
Cooperative Institute for Research in Environmental Sciences
NOAA/OAR/ESRL/Global Systems Division
Boulder, CO
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