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</pre><p>However, we must recall that the sst grid corresponds to equally spaced latitudes and longitudes, which are <b>not</b> all equal in area. Lines of longitude converge at the poles, so an area-averaged measure of SST requires weighting the mean by are of each grid cell.</p><p>To accomplish this, turn the <tt>lat</tt> and <tt>lon</tt> arrays into grids and use <a href="cdtarea_documentation.html"><tt>cdtarea</tt></a> to get the area of each grid cell. Here are the areas of each grid cell:</p><pre c