[ncl-talk] using gc_inout over the Central Arctic

[Rym Msadek]

Hi,

I am trying to use the gc_inout function to define a polygon over the Arctic region and use that as a mask to average an oceanic field like potential temperature.
I have an issue when the longitudes and latitudes of the polygon cover a region that crosses the North pole. gcinout gives me a contour that is not closed and I can’t figure out how to overcome this issue.

Here are the lon lat that define my polygon, over the Eurasian basin of the Arctic.
---------
latC=(/81,81.5,82,82.7,82.4,81.6,80,78.8,77,78,79,81,82,84,88,88.5,89,86,85,85,84,83,82,82,81/)
lonC=(/27,36,48,60,77,94,107,114,121,134,140,141,145,149,132,149,-79,-55,-43,-22,-20,-17,-9,5,27/)

in_obs=gc_inout(nav_lono,nav_lato,lonC,latC)

mask_eurasia = where(in_obs.eq.True,1,0)
plot= gsn_csm_contour_map_polar(wks,mask_eurasia,res)
--------
I’m attaching the resulting plot that I get.
Note that I have used this same gc_inout function to define other polygons in the Arctic and it works fine when the region was not over the central Arctic.

Any help would be appreciated.

Thanks,

Rym

------
Rym Msadek
CNRS-CERFACS
42 Avenue Gaspard Coriolis
31057 Toulouse
Tel: 05 61 19 31 92
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20161201/8eaa1d9c/attachment.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: eurasian_mask.png
Type: image/png
Size: 208700 bytes
Desc: not available
Url : http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20161201/8eaa1d9c/attachment.png