The Secondary Flow near a Baroclinic Planetary Wave Critical Line

Abstract

The wave-mean flow interaction has been computed near an energy-absorbing, baroclinic, planetary wave critical line tilted at an arbitrary angle from the vertical. This problem is a generalization of the critical line interaction problems studied by Matsuno and Nakamura (1979) and Schoeberl (1980). A tilted critical line can directly tap the eddy heat transport of a Rossby wave and produce a singular rate of change in the zonally averaged temperature at the critical line. This implies that sudden stratospheric warmings may not always require an induced Eulerian-mean secondary circulation to create significant temperature changes in the zonally averaged flow as suggested by Matsuno (1971). Strong Lagrangian-mean motion also exists along the critical line if it is not perfectly vertical. These results are discussed with application to the 1976/77 sudden warming.