The role of orographically and thermally forced stationary waves in the causation of the residual circulation

Abstract

Several experiments performed with an idealized troposphere-stratosphere GCM are compared to estimate the impact of orography and prescribed local heat sources on the residual circulation in the northern winter stratosphere. It is found that only the combined action of orographic and thermal wave forcing in northern midlatitudes is capable of inducing a residual circulation reaching continuously from tropical to polar latitudes at stratospheric altitudes. Intensifications of the residual circulation in response to modified forcing of stationary waves are generally associated with, firstly, a reduced polar night jet accompanied by enhanced easterlies in low and summer hemispheric latitudes and, secondly, substantial warming of the polar night stratosphere completely compensated by cooling in the tropics and subtropics.