A Comparison of Primitive and Balance Equation Simulations of Baroclinic Waves

Abstract

The balance equations are an approximate set of equations that reduce to gradient wind balance under steady, circular flow conditions on an f plane. Scale analysis indicates that these equations are potentially quite accurate over a wide variety of atmospheric conditions. Motivated by an apparent lack of numerical solutions of this set, we compare simulations of nonlinear baroclinic waves under adiabatic conditions with the primitive and balance equations. As predicted by the scale analysis, the balance equations describe the wave evolution with very high accuracy in situations where the errors made by approximate equation sets based on geostrophy are significant.