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20051013: Decimating winds in GDCROSS

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  • Subject: 20051013: Decimating winds in GDCROSS
  • Date: Fri, 14 Oct 2005 13:34:29 -0600
John,

IJSKIP may help you in gdcross. For example, in your N/S cross section,
using IJSKIP=2 seems to produce a decent spatial filtering for the RUC20km.
Actually, the Jskip is the control in a N/S cross section.

If your need is to filter in the vertical of the cross section, then
using the VMSK function in the GVECT, and masking values where the pressure 
is not an even multiple of some delta-p can be done.

As an example, using the test of the remainder of a quotient for zero
as the mask such as:
GVECT    = vmsk(obs,sle(sub(quo(pres,100),int(quo(pres,100))),0))

produces a filter where the remainder of quo(pres,100)=0, 
so the OBS vectors are only plotted where filter <= 0 is true, which
is the 100mb pressure level intervals.

Chiz


Steve Chiswell
Unidata User Support


>From: John Merrill <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200510131909.j9DJ9Y7s006039

>Hello,
>   Further in regard to decimating wind fields for use in GDCROSS.
>
>   Oh, here's a possibility that came to mind. I could create a
>variable field with ZERO values at most grid boxes, and UNITY
>in a select few. Then I could MULtiply the wind components by
>this and plot the result. Now all I need to do is create such
>a multiplicative field; GDEDIT should accommodate this. I would
>use GDDIAG to set up the calculation, in a way parallel with
>something you showed me recently for filling a grid with
>tropopause-relative pressure values.      John M.
>
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