The Effects of Transience on the Propagation of Stratospheric Planetary Waves

Abstract

The propagation of planetary-scale Rossby waves in the stratosphere is investigated in a linear, time-dependent, primitive equation model. Two distinct maxima in the convergence of the Eliassen-Palm flux (EP flux) are found for steady and for transient waves in a variety of realistic Northern hemisphere, winter season, zonal flows; one below the stratospheric polar jet and the other north of the zero wind line. These maxima appear at higher altitudes for wave 1 than for wave 2, especially in low latitudes. Different mechanisms cause the formation of these two maxima. The confinement of wave activity in high latitudes is mainly due to the dissipation of waves in that region under non-WKBJ conditions. The maximum in lower latitudes is related to the absorption of Rossby waves near their critical lines. For wave 2, the intensity of the high latitude maximum is sensitive to the transience of the wave forcing at the tropopause, while for wave 1 this sensitivity is reduced. For both waves the low latitude maximum shifts northward with increasing transience.