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NCL Graphics: POP Scalars

POP data that have 2D lat/lon coordinates can be plotted directly in physical space. To do this, simply read in the two dimensional arrays containing the grid point coordinates and assign the arrays to the variable to be plotted as attributes with the specific names lon2d and lat2d:
       lat2d     = f->TLAT
       lon2d     = f->TLONG
       t@lon2d   = lon2d
       t@lat2d   = lat2d
popscal_1.ncl: A black and white plot.
popscal_2.ncl: Shades values less than five.

The gsn_contour_shade function fills contours less than/greater than or equal to the numeric arguments passed to it. Whether or not to fill with color or pattern, and which color/pattern to fill high/middle/low ranges with, are determined by attributes attached to the "opt" argument. Detailed information about gsn_contour_shade can be found on the function's documentation page on the NCL website.

There are many other contour effects that you can use for your own contour plots.
popscal_3.ncl: Creates a color plot

The color fill example page is a good resource for learning about color plots.
popscal_4.ncl: Shows how to draw vectors over scalars on another projection. You are not limited to cylindrical equidistant projections. There are several projections to choose from.

This is an orthographic projection. If you wish to view a CE projection, gsn_csm_vector_scalar_map_ce is the function to use: Example.
popscal_5.ncl: Demonstrates how to overlay contours on a contour/map plot.