# Geostrophic coordinates

From AMS Glossary

## geostrophic coordinates

The coordinate system used in the semigeostrophic equations.

Geostrophic coordinates ( where

*X*,*Y*,*Z*,*T*) are related to physical space coordinates (*x*,*y*,*z*,*t*) by*u*_{g}and*v*_{g}are the eastward and northward geostrophic winds and*f*is the Coriolis parameter. Through this coordinate transform the semigeostrophic equations arise. The geostrophic approximation is not used as frequently in the semigeostrophic equations as in the quasigeostrophic equations; thus the semigeostrophic equations produce a more accurate representation of certain phenomena, such as fronts and jets.