Re: [gembud] GEMPAK Script Question

• To: Steve Decker <sgdecker@xxxxxxxxxxxxxxxxxx>
• Subject: Re: [gembud] GEMPAK Script Question
• From: Jeffrey Krob - NOAA Federal <jeffrey.a.krob@xxxxxxxx>
• Date: Wed, 12 Feb 2020 09:10:14 -0500

Thanks for the replies...but that raises a bigger question concerning the
execution of the formula. For example, the 'quo(urel,mag(vecr(urel,0)))'
portion. As I understand it, working from 'inside-out',
vecr(urel,0)  will result in V1 = urel & V2 = 0 for each grid point. Then,
the mag(V1,V2) will always be the value of V1 ( SQRT(V1*V1) + (V2*V2) )
since 0*0=0 & the square root of V1*V1 is...V1. Next, 'quo(urel,V1)' will
always yield 1 since v1 still equals urel. What is the purpose of jumping
through all those hoops if the answer is always "1"...or am I missing
something?

BTW - this is from some NCEP post processing routine to calculate slantwise
CAPE. This portion calculates 'alpha' where the in-line comment states:
"alpha...with u and v can use alpha to get momentum as needed."

Thanks again,
Jeff

On Tue, Feb 11, 2020 at 11:22 AM Steve Decker <sgdecker@xxxxxxxxxxxxxxxxxx>
wrote:

> Jeff,
>
> That would be my interpretation.  It's essentially constructing the zonal
> wind (actually the left-to-right wind on the grid since urel is used) as a
> vector.
>
> Cheers,
> Steve
>
> On 2/11/20 10:57 AM, Jeffrey Krob - NOAA Federal via gembud wrote:
>
> All,
>
> GEMPAK 'newbie' here - came across a script which is passed to the
> DG_GRIDN routine as the following:
>
> custar =
> 'mul(acos(quo(mul(mag(vasv(vecr(urel,0),geo)),quo(urel,mag(vecr(urel,0)))),urel)),RTD)'
>
> Question; concerning the 'vecr(urel,0)' portion, I understand this is a
> call to the DV_VECR (S1, S2) routine to create a vector from 2 scalars.
> However, with the second argument being a '0', is this only returning the
> 'U' portion of the U/V wind vector or is something else going on here?
>
> Thanks in advance,
> Jeff Krob
> NOAA/NESDIS
>
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• References:
  • [gembud] GEMPAK Script Question
    • From: Jeffrey Krob - NOAA Federal