Movement and Vertical Coupling of Adiabatic Baroclinic Tropical Cyclones

The movement and vertical coupling of an adiabtic baroclinic tropical cyclone (TC) are investigated through numerical experiments, in which the TC is affected by either the vertical environmental shear or differential beta drift. In both cases, the response of the initially symmetric baroclinic vortex is to tilt in the vertical. In association with the vertical tilt, as required by the nonlinear balance, the wavenumber-one PV anomalies develop with the positive anomaly downtilt (uptilt) above (below) the maximum PV level. As a result, a three dimensional mesoscale asymmetric circulation develops within an initially symmetric baroclinic vortex. On a beta plane, in addition to the beta gyres, the counter-rotating inner gyres are centered at the radius of maximum wind. The TC motion differs from the advection of the symmetric PV component by the asymmetric flow. It is also determined by the horizontal advection of the asymmetric PV anomalies by the symmetric cyclonic flow (AASF) and the vertical PV advection associated with the asymmetric vertical motion. These processes also play an important role in the vertical coupling because of the vertical PV structure of a baroclinic TC.