Re: plotting grid sub-regions

Hi Dave,
I downloaded your tar file, and looked at the 2 plots. I didn't see
anything that I thought was outside the bounds of looking at the data
via different projections, so I forwarded it to the ncl-developers. A
response:
"It sounds like what he is referring to is the way the lower right part
of the grid in his subset plot curve, whereas they are straight in the
full plot. I bet this is just because the center lon and lat have
different values in the two plots. If he plotted the lat/lon grid on his
subset plot he would probably find that the grid lines follow the curve
of his grid."

Hope that helps..
Adam

On 04/28/2010 10:05 AM, David B. Reusch wrote:
> Hello,
>
> I have been trying to figure out a way to plot a subset of my data (from
> MM5, so with 2-d lat and lon data) that is bounded by four corner points
> with four unique lat and lon values. I know how to use upper/lower lats
> and left/right longs to plot a map bounded by lats and longs, but that
> doesn't work as I'd like in the high latitudes of interest (south of 60 S).
>
> Another way of thinking about this is that I have a nice rectangle in
> the i,j-grid space with i and j values analogous to the
> minLat/maxLat/minLon/maxLon values used for mpLimitMode="LatLon". Of
> course those i,j values correspond to four unique pairs of lat/long
> values in lat/lon space, thereby creating the problem I've been unable
> to solve.
>
> Specifically, I'd like to use something like these corners to subset (in
> clockwise order):
> 60 S, 55 W
> 72 S, 20 W
> 84 S, 102 W
> 67 S, 93 W
>
> My best result so far comes from using mpLimitMode="Corners" (LeftCorner
> = -67,-93, RightCorner = -72,-20) and mpProjection="Stereographic" with
> gsn_csm_contour_map. This seems really close to what I want but when I
> compare it to the result from using gsn_csm_contour_map_polar (i.e., a
> full south polar map in "polar sterographic") I see some differences in
> scaling as I move towards the pole (i.e., areal distortion) that I'm not
> comfortable with. Is it possible I'm just seeing irreconciliable
> differences between the projections? If not, what am I missing to get
> to where I want to be?
>
> I have put a tar-file (ncl_test.tgz) with all the related files at
> http://public.me.com/dbreusch. If the above text is unclear, hopefully
> the plots included in this file will explain things better.
>
> Thanks!
> Dave
>

-- 
__________________________________________________
Adam Phillips 
asphilli@ucar.edu
National Center for Atmospheric Research   tel: (303) 497-1726
Climate and Global Dynamics Division         fax: (303) 497-1333
P.O. Box 3000				
Boulder, CO 80307-3000    http://www.cgd.ucar.edu/cas/asphilli
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