The Generation and Maintenance of Hollow PV Towers in a Forced Primitive Equation Model

Proceedings

Williams Jr., Gabriel J.¹ 

关键词: hurricane;    tropical cyclone;    tropical cyclone structure;    potential vorticity;    hollow PV tower;    vortex dynamics;    vortex instability;   

DOI  :  10.3390/ecas2017-04149

学科分类：社会科学、人文和艺术（综合）

来源: mdpi

【 摘 要 】

Diabatic heating from deep moist convection in the hurricane eyewall produces a towering annular structure of elevated potential vorticity (PV), known as a hollow PV tower. For sufficiently thin annular structures, eddies can extract energy from the mean flow, leading to hollow tower breakdown with significant changes in vortex structure and intensity. A forced primitive equation model in isentropic coordinates is used to understand the role of diabatic heating in the generation, maintenance, and breakdown of the hurricane PV tower. It is shown that diabatic heating produces a strengthening and thinning PV tower in time due to the combined effects of the diabatic heating and the radial PV advection by the induced secondary circulation. If the forcing makes the eyewall thin enough, then the PV tower can become dynamically unstable and cause air parcels with high PV to be mixed preferentially into the eye at lower levels, where unstable PV wave growth rates are largest. The breakdown of the hollow PV tower leads to a transient break in vortex intensification, a decrease in minimum central pressure, and an inward shift and tilt of absolute angular momentum surfaces. It is shown that the maintenance of the PV tower structure depends on the strength of the heating-induced secondary circulation.

【 授权许可】

CC BY