Effects of convective heating on movement and vertical coupling of tropical cyclones: A numerical study

The influence of convective heating on movement and vertical coupling of tr opical cyclones (TCs) is investigated using a hurricane model with differen t environmental flows. The authors identify two processes by which convecti ve heating may affect TC motion. One is the advection of symmetric potentia l vorticity (PV) by heating-induced asymmetric flow. The other is the direc t generation of a positive PV tendency by asymmetric heating, which acts to shift a TC to the region of maximum downward gradient of asymmetric heatin g. A steering level exists that is located at the level where the direct in fluence of asymmetric heating vanishes, normally in the lower troposphere. At that level, a TC moves with the asymmetric flow averaged within a radius of 200 km, because the influence of asymmetric flows on TC motion is weigh ted by the horizontal PV gradient that is primarily confined within the TC core. Although the vertical shear in the asymmetric flow (including environ mental and heating-induced flows) could tilt the vortex, the influence of a symmetric heating tends to offset the vertical tilt caused by the vertical shear through a fast adjustment between the asymmetric wind and diabatic he ating. Therefore, diabatic heating enhances the vertical coupling.