Abstract
The vertical coupling (VC) process and mechanism during the genesis of a tropical cyclone (TC) implied by the weak vertical shear of horizontal wind, one of the key factors impacting TC genesis, constitute important but unanswered fundamental scientific problems. This paper carried out a targeted investigation of this problem through numerical simulation and theoretical analyses. The main conclusions are as follows. Even if TC genesis occurs in a barotropic environment, a VC process still occurs between the trough (vortex) at the middle level and that at the lower level in the TC embryo area. VC mainly occurs at the tropical disturbance (TDS) stage. Only after the VC is accomplished can the tropical depression (TD) organize further by itself and develop into the tropical storm (TS) stage or the stronger tropical typhoon (TY) stage through the WISHE (wind-induced surface heat exchange) mechanism. In the VC process, vortical hot towers (VHTs) play vertical connecting roles and are the actual practitioners of the VC. Through the VHTs’ vertical connections, the middle- and lower-troposphere trough axes move towards each other and realize the VC. VHTs can produce intensive cyclonic vorticity in the lower troposphere, which is mainly contributed by the stretching term. The tilting term can produce a single dipole or double dipole of vorticity, but the positive and negative vorticity pairs offset each other roughly. While the stretching term ensures that the cyclonic rotations of the wind field in the middle and lower levels tend to be consistent, the tilting term acts to uniformly distribute the horizontal wind in the vertical direction, and both terms facilitate the VC of the wind field. With the latent heat of condensation, VHTs heat the upper and middle troposphere so that the 352 K equivalent potential temperature contour penetrates vertically into the 925–300 hPa layer, realizing the VC of the temperature field. While forming cloud towers, VHTs make the ambient air become moist and nearly saturated so that the 95% relative humidity contour penetrates vertically into the 925–400 hPa layer, realizing the VC of the humidity field. Due to the collective contributions of the VHTs, the embryo area develops into a warm, nearly saturated core with strong cyclonic vorticity. The barotropic instability mechanism may also occur during TC genesis over the Northwest Pacific and provide rich large-scale environmental vorticity for TC genesis. The axisymmetric distribution of VHTs is an important sign of TC genesis. When a TC is about to form, there may be accompanying phenomena between the axisymmetric process of VHTs and vortex Rossby waves.
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References
Cecelski S F, Zhang D L. 2013. Genesis of hurricane Julia (2010) within an African easterly wave: Low-level vortices and upper-level warming. J Atmos Sci, 70: 3799–3817
Chen L S, Ding Y H. 1979. The Conspectus of Western Pacific Typhoon (in Chinese). Beijing: Science Press. 107–109
China Meteorological Administration. 2002. Yearbook of Tropical Cyclone (2001) (in Chinese). Beijing: China Meteorological Press
Davis C A, Bosart L F. 2001. Numerical simulations of the genesis of hurricane Diana (1984). Part I: Control simulation. Mon Weather Rev, 129: 1859–1881
Emanuel K A. 1986. An air-sea interaction theory for tropical cyclones. Part I: Steady state maintenance. J Atmos Sci, 43: 585–605
Emanuel K A. 1989. The finite-amplitude nature of tropical cyclogenesis. J Atmos Sci, 46: 3431–3456
Gray W M. 1968. Global view of the origin of tropical disturbances and storms. Mon Weather Rev, 96: 669–700
Hendricks E A, Montgomery M T, Davis C A. 2004. On the role of “vortical” hot towers in formation of tropical cyclone Diana (1984). J Atmos Sci, 61: 1209–1232
Kasahara A. 1961. A numerical experiment on the development of tropical cyclone. J Meteorol, 18: 259–282
Kurihara Y, Bender M A, Ross R J. 1993. An initialization scheme of hurricane models by vortex specification. Mon Weather Rev, 121: 2030–2045
Lee C S, Lin Y L, Cheung K K W. 2006. Tropical cyclone formations in the South China Sea associated with the Mei-Yu front. Mon Weather Rev, 134: 2670–2687
Liu Y, Zhang D L, Yau M K. 1997. A multiscale numerical study of hurricane Andrew (1992). Part I: Explicit simulation and verification. Mon Weather Rev, 125: 3073–3093
Lord S J, Willoughby H E, Piotrowicz J M. 1984. Role of a parameterized ice-phase microphysics in an axisymmetric, nonhydrostatic tropical cyclone model. J Atmos Sci, 41: 2836–2848
Lu M Z, Peng Y Q. 1990. Dynamic Meteorology (in Chinese). Beijing: China Meteorological Press. 390
Montgomery M T, Enagonio J. 1998. Tropical cyclogenesis via convectively forced vortex Rossby waves in a three-dimensional quasigeostrophic model. J Atmos Sci, 55: 3176–3207
Montgomery M T, Nicholls M E, Cram T A, Saunders A B. 2006. A vortical hot tower route to cyclogenesis. J Atmos Sci, 63: 355–386
Nolan D S. 2007. What is the trigger for tropical cyclogenesis? Aust Meteorol Mag, 56: 241–266
Ooyama K. 1969. Numerical simulation of the life cycle of tropical cyclones. J Atmos Sci, 26: 3–40
Rotunno R, Emanuel K A. 1987. An air-sea interaction theory for tropical cyclones. Part II: Evolutionary study using a non-hydrostatic axisym-metric numerical model. J Atmos Sci, 44: 542–561
Sundqvist H. 1970. Numerical simulation of the development of tropical cyclones with a ten-level model. Part I. Tellus, 22: 359–390
Tuleya R E, Kurihara Y. 1981. A numerical study on the effects of environmental flow on tropical storm genesis. Mon Weather Rev, 109: 2487–2506
Wang Y P, Cui X P, Li X F, Zhang W L. 2016. Kinetic energy budget during the genesis period of tropical cyclone Durian (2001) in the South China Sea. Mon Weather Rev, 144: 2831–2854
Wang Z. 2014. Role of cumulus congestus in tropical cyclone formation in a high-resolution numerical model simulation. J Atmos Sci, 71: 1681–1700
Wang Z. 2018. What is the key feature of convection leading up to tropical cyclone formation? J Atmos Sci, 75: 1609–1629
Willoughby H E, Jin H L, Lord S J, Piotrowicz J M. 1984. Hurricane structure and evolution as simulated by an axisymmetric, nonhydrostatic numerical model. J Atmos Sci, 41: 1169–1186
Yamasaki M. 1977. A preliminary experiment of the tropical cyclone without parameterizing the effects of cumulus convection. J Meteorol Soc Jpn, 55: 11–31
Zehr R M. 1992. Tropical Cyclogenesis in the Western North Pacific. NOAA Tech Rep. NESDIS 61, 3
Zhang D L, Tian L Q, Yang M J. 2011. Genesis of Typhoon Nari (2001) from a mesoscale convective system. J Geophys Res, 116: D23104
Zhang Q H, Guo C R. 2008. Overview of the studies on tropical cyclone genesis (in Chinese). Acta Ocean Sin, 30: 1–11
Zhang W L, Cui X P. 2013. Review of the studies on tropical cyclone genesis (in Chinese). J Trop Meteorol, 29: 337–346
Zhang W L, Cui X P, Dong J X. 2010. The role of the middle tropospheric mesoscale vortex in the genesis of typhoon Durian (2001) (in Chinese). Chin J Atmos Sci, 34: 45–57
Zhang W L, Cui X P, Wang A S, Zong Z P. 2008b. Numerical simulation of hot towers during pre-genesis stage of typhoon Durian (2001) (in Chinese). J Trop Meteorol, 24: 619–628
Zhang W L, Wang A S, Cui X P. 2008a. The role of the middle tropospheric mesoscale vortex in the genesis of Typhoon Durian (2001)-simulation and verification (in Chinese). Chin J Atmosph Sci, 32: 1197–1209
Zhang W L, Zhang D L, Wang A S, Cui X P. 2009. An investigation of the genesis of typhoon Durian (2001) from a monsoon trough (in Chinese). Acta Meteorol Sin, 67: 811–827
Zhu L, Zhang D L, Cecelski S F, Shen X. 2015. Genesis of tropical storm Debby (2006) within an African Easterly Wave: Roles of the bottom-up and midlevel pouch processes. J Atmos Sci, 72: 2267–2285
Acknowledgements
This work was supported by the National Basic Research Program of China (Grant No. 2015CB452804) and the National Natural Science Foundation of China (Grant No. 41475051). We thank the two anonymous reviewers for their valuable comments and constructive suggestions.
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Zhang, W., Cui, X. & Dong, J. Characteristics and mechanism of vertical coupling in the genesis of tropical cyclone Durian (2001). Sci. China Earth Sci. 64, 440–457 (2021). https://doi.org/10.1007/s11430-019-9681-x
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DOI: https://doi.org/10.1007/s11430-019-9681-x