Sensitivity of Tropical Cyclone Intensification to Axisymmetric Heat Sources: The Role of Inertial Stability

Abstract

his study examines the influences of an axisymmetric heat source on the tangential wind structure of a tropical cyclone (TC). Specifically, the response of a TC due to the effect of convection located in varying inertial stability profiles was calculated. Using an idealized heat source, the thermodynamic efficiency hypothesis and the dynamic hypothesis for lower level tangential wind acceleration are studied with the use of a balanced 2-D model. These two frameworks for calculating the lower level tangential wind acceleration are then compared to an idealized but thermally forced version of a non-linear 3-D model (WRF). It is found that using either of the 2-D balanced model approaches to calculate the tangential wind acceleration results in an underestimation when compared to the full non-linear simulation. In addition, the thermodynamic efficiency approach also shows a radial shift in the location of the maximum lower level tangential wind acceleration. Sensitivity experiments in the context of the WRF model in varying background inertial instabilities were investigated. It is shown that as the eyewall-like heating is shifted to larger values of inertial stability there is a decrease in the induced secondary circulation in tandem with a spin up of the lower level tangential winds. This intensification appears to be modulated by the low level radial advection of absolute vorticity.