A Potential Vorticity Tendency Diagnostic Approach for Tropical Cyclone Motion*

Abstract

In order to understand the roles of various physical processes in baroclinic tropical cyclone (TC) motion and the vertical coupling between the upper-and lower-level circulations, a new dynamical framework is advanced. A TC is treated as a positive potential vorticity (PV) anomaly from environmental flows, and its motion is linked to the positive PV tendency. It is shown that a baroclinic TC moves to the region where the azimuthal wavenumber one component of the PV tendency reaches a maximum, but does not necessarily follow the ventilation flow (the asymmetric flow over the TC center). The contributions of individual physical processes to TC motion are equivalent to their contributions to the wavenumber one PV component of the PV tendency. A PV tendency diagnostic approach is described based on this framework. This approach is evaluated with idealized numerical experiments using a realistic hurricane model. The approach is capable of estimating TC propagation with a suitable accuracy and determining fractional contributions of individual physical processes (horizontal and vertical advection, diabatic heating, and friction) to motion. Since the impact of the ventilation flow is also included as a part of the influence of horizontal PV advection, this dynamical framework is more general and particularly useful in understanding the physical mechanisms of baroclinic and diabatic TC motion.

Effects of Landfall Location and Approach Angle of an Idealized Tropical Cyclone over a Long Mountain Range

“…Note that in the present study, we found that the vorticity tendency (VT) approach is appropriate since the TC track is consistent with the VT, similar to that applied to TC motion, such as northwestward beta drift (e.g., Holland, 1983) and shear effects (e.g., Wu and Emanuel, 1993). The PV Tendency (PVT) diagnostic approach, as originally proposed by Wu and Wang (2000) and Chan et al (2002) and applied to real-case simulations (e.g., Hsu et al, 2013;Chan, 2013, 2014;Wang et al, 2013), appears to be an attractive method and will be considered in our future research. …”

“…In addition, unlike a dry cyclone vortex used in LS11 and L05, a more realistic bogus TC is initiated in a conditionally unstable atmosphere with land surface, moist and planetary boundary layer (PBL) processes included. A vorticity budget analysis is adopted to help understand the effects of combined forcing of orography and convection, instead of the potential vorticity tendency (PVT) diagnostic approach taken by some previous studies (e.g., Wu and Wang, 2000;Chan et al, 2002;Hsu et al, 2013;Chan, 2013, 2014;Wang et al, 2013). The direct diabatic heating effects will be investigated along with the rainfall distributions.…”

Effect of Sea Surface Temperature Gradient Induced by the Previous Typhoon's Cold Wake on the Track of the Following Typhoon: Bolaven (1215) and Tembin (1214)

“…60초 간격으로 72시간 동안 적분을 하였다. 물리과 정으로, 적운 모수화에는 Kain-Fritsch scheme이 이 용되었고 (Kain and Fritsch, 1993), 경계층 모수화에 (Wu and Wang, 2000;Chan et al, 2002;Wong and Chan, 2006). 시그마좌표계에서 파수 1 성분의 잠재와도 경 향방정식은 다음 식(1)과 같이 나타낼 수 있다 (Wu and Wang, 2000).…”

“…물리과 정으로, 적운 모수화에는 Kain-Fritsch scheme이 이 용되었고 (Kain and Fritsch, 1993), 경계층 모수화에 (Wu and Wang, 2000;Chan et al, 2002;Wong and Chan, 2006). 시그마좌표계에서 파수 1 성분의 잠재와도 경 향방정식은 다음 식(1)과 같이 나타낼 수 있다 (Wu and Wang, 2000). (Fiorino and Elsberry, 1989;Wang and Holland 1996a, 1996b, 1996cChan and Cheung, 1998;Wong and Chan, 2006).…”

Upper-tropospheric environment–tropical cyclone interactions over the western North Pacific: A statistical study

“…The PV perspective is not only applicable to TC motion (e.g., Wu and Wang, 2000;Chan et al, 2002;Choi et al, 2013), but also to TC intensity change (e.g., Molinari et al, 1998). Molinari et al (1998Molinari et al ( , 1995 also applied the PV perspective to interaction cases, in which interaction could be viewed as an upper-level synoptic PV anomaly (the environment) interacting with a lower-level mesoscale PV anomaly (the TC).…”