OpenIFS uses the so-called 'Gaussian grid' to represent variables in physical space. A Gaussian grid does not have regular latitude spacing but nearly so. The latitudes are determined by the zeros in the Gaussian quadrature used in the Legendre polynomials.

A Gaussian grid does not have a latitude at the equator, nor exactly at the poles. The latitudes are symmetric about the equator.

The model uses several representations of a Gaussian grid as explained below.

Examples

Gaussian grid with 320 latitudes between pole and equator

Gaussian grid with 640 latitudes between pole and equator

Gaussian grid with 1280 latitudes between pole and equator