On the (Nearly) Symmetric Instability

Abstract

It is shown in the limit of small Ekman number that the preferred mode of the symmetric instability exhibits a slight angle of inclination with the direction of the mean flow. The sign of the angle depends an the sign of P 1, where P is the Prandtl number. It is likely that owing to this effect the range of Richardson numbers for which the instability occurs is increased significantly beyond the limits derived by Kuo (1956) and by {McIntyre} (1970). Numerical computations are needed to establish this property quantitatively.