Two-Dimensional Response of a Stably Stratified Shear Flow to Diabatic Heating

Abstract

A two-dimensional, linearized problem in a stratified shell flow with either isolated heating or differential heating is investigated. In response to isolated heating with the heating top below the wind reversal height, the low-level vertical velocity near the heating center may be positive or negative depending upon the Richardson number associated with the basic flow and the depth of the heating layer. The phenomenon can be explained by the advection effect of the basic flow. In response to differential heating associated with the low-level temperature contrast, a sharp contrast of upward and downward motion is produced near the center of the differential heating. Similar to the isolated heating case, the low-level upward motion may be located over the warm or cold side. Convection may be triggered or maintained if the upward motion is located over the side where the supply of moisture is abundant in a mesoscale circulation. In response to thermal forcing in the vicinity of the critical level, the vertical velocity is almost positive near the heating center in the heating layer for a wide range of Richardson number. The consistency of the vertical motion and the heating at the heating base is important in supporting the existing convection. The disturbance is mainly a superposition of the gravity waves generated separately by the heating from below and above the critical level. The condensational heating in the vicinity of the critical level may play an important role, in the interaction of the flow below and above the critical level in a moist convection.