Use the MERIDIONAL keyword to correct for the convergence of longitude lines at the poles. When deriving divergence and stretching deformation grids (DVG and DST), specify MERIDIONAL=YES to subtract the following correction term from the calculation.

When deriving vorticity, absolute vorticity, or shear deformation grids (VOR, ABV, or DSH), specify MERIDIONAL=YES to add the following correction term to the calculation.

For both the correction terms above:

u = u-component of the wind

v = v-component of the wind

f = latitude in degrees

r = radius, in kilometers, of the planet at f latitude