Makes sense. I didn't consider the polarity.
Thanks again,
Jeff
On Wed, Feb 12, 2020 at 9:47 AM Steven Decker <sgdecker@xxxxxxxxxxxxxxxxxx>
wrote:
> I think the idea for that part of the calculation is to return -1 if urel
> is negative and +1 if urel is positive.
>
> Steve
>
> On Feb 12, 2020 9:10 AM, Jeffrey Krob - NOAA Federal <
> jeffrey.a.krob@xxxxxxxx> wrote:
> 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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