[gradsusr] Centroid of Polar Vortex

[Jeff Duda]

First, define a variable that only includes the area contained within the
5400 contour.  The following will do the trick:

"define vortex = const(maskout(height,5400),1)"

Then compute the centroid.

"define xsum = sum(lon,[some horizontal limit that fits the entire contour
within it])"
"define ysum = sum(lat,[some meridional limit that fits the entire contour
within it])"
longitude of centroid: "d xsum / asum(vortex,[x limits],[y limits])"
latitude of centroid: "d ysum / asum(vortex,[x limits],[y limits])"


Jeff Duda

On Sun, Apr 8, 2012 at 11:14 PM, Abdolreza Kashki <r.kashki at yahoo.com>wrote:

> Dear all,
> How can I calculate the Centriod(lat,lon) of a specific contour e.g. 5400
> gpm contour in 500 hpa level in degree in Grads software?
> Best Regards
> kashki
>
> Abdolreza Kashki
> Ph.D. Student of Climatology
> Department of Physical Geography
> Faculty of Planing & Geography Science
> University of Isfahan
> Isfahan, Iran
> Postcode:81746-73441
> Tel:+98(311)7933119
> Fax:+98(311)7932257
> Cell:+989151731453
>
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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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