Re: About performing calculation in the specific area

From: Mary Haley <haley_at_nyahnyahspammersnyahnyah>
Date: Tue Feb 07 2012 - 15:00:23 MST

Please see the gc_inout function, if you want to mask your data based on a lat/lon polygon:

http://www.ncl.ucar.edu/Document/Functions/Built-in/gc_inout.shtml

We've used this function in conjunction with shapefiles, where we use polygons on the shapefile for masking purposes. See:

http://www.ncl.ucar.edu/Applications/shapefiles.shtml

--Mary

On Feb 7, 2012, at 9:49 AM, Ng, Kelvin wrote:

> Hi,
>
> The question is how to do calculation in the specific area using NCL. What we are trying to do is to calculate cyclone thermal symmetry within 500 km radius. The method that we are thinking about is to use a circular mask that only constraint NCL to do pick out data inside the circular region with 500 km radius. Then divided the circle into half with the vector which determine by the direction of the cyclone movement. Perform the calculation in both semi-circular region.
>
> But
> 1) How to isolate such region out?
> 2) How to make such region circular?
>
> (OR how to make 2 semi-circle which can be combine as a circle, in this way, the calculation is easier.)
>
> Hope these questions are clear enough.
>
> Regards,
>
> Kelvin
>
> PS: we are trying to use the method which is suggested in "A cyclone phase space derived from thermal wind and thermal asymmetry" by Robert E. Hart
> _______________________________________________
> ncl-talk mailing list
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk

_______________________________________________
ncl-talk mailing list
List instructions, subscriber options, unsubscribe:
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Tue Feb 7 15:00:34 2012

This archive was generated by hypermail 2.1.8 : Thu Feb 09 2012 - 13:33:26 MST