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Zhao Kun 1,2 and Ben Jong-Dao Jou 1

The evolution and dynamics of an oceanic quasi-linear convective system occurred on Sept. 10, 2004 over the Taiwan Strait. Zhao Kun 1,2 and Ben Jong-Dao Jou 1 1 Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan

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Zhao Kun 1,2 and Ben Jong-Dao Jou 1

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  1. The evolution and dynamics of an oceanic quasi-linear convective system occurred on Sept. 10, 2004 over the Taiwan Strait Zhao Kun1,2 and Ben Jong-Dao Jou1 1Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan 2The key laboratory of Mesoscale Severe Weather, Department of Atmospheric Sciences Nanjing University, Nanjing China Oct.31, 2006Boulder

  2. Outline • Background, case description • Dual-Doppler synthsis (kinematic structure and thermodynamic/dynamic retrieval) and results analysis • Discussion on origin, longevity, and the upscale growth of the mesovortex • Conclusions

  3. QLCS#1 QLCS#2 QLCS#5 QLCS#3 QLCS#4

  4. B A Develop-Mature -Decay 1.5h A+B Redevelop 1.5h Decay 1.5h

  5. Dual-Doppler Analysis • RCTP and RCWF Radars, baseline 60km • 1.5 hour period, total of 15 analysis volumns • Grid spacing: 1000m X 1000 m X 500m • Domain: 60 km X 60 km X 16 km • Boundary conditions: W=0 at upper and lower boundaries • Horizontal field at echo top are lightly smoothed with two pass Leise filter prior to divergencecalculation and vertical integration for W Thermodynamic Retrieval: Roux et al.(1990)

  6. Mature stage of mesovortex: after merge, a balanced feature? Houze et al. 1989

  7. Mesovortices in QLCS#1 CELL V#1 V#2 V#1 V#3 V#2

  8. Vortex Merge V#1+V#3

  9. V#1 V#1 V#2 0634UTC

  10. V#1 V#3 V#2 0709UTC

  11. V#3 0750UTC

  12. Themodynamic Fields at 0750UTC 2km P’(0.1mb) T’(0.1o) W L 4km L W

  13. Thermodynamic diagnose For the vortex at mature stage

  14. Cross section A A’ B B’ C C’

  15. Time-height profiles of the average vorticity and divergence within the vortex 1 and 3 VORTEX#1 VORTEX#3

  16. Vorticity Budget

  17. 0750UTC 0709UTC

  18. Discussion (1) Origin of vortex 0657UTC 0750UTC Stretching + Tilting (?)

  19. (2) Longevity of Vortex Vortex Rossby Radius(Frank 1983) Durran and Klemp (1982) MaKung Sounding Taipei Sounding Different Environment Dynamical large Dynamical small

  20. (3) Upscale growth of Vortex Merger (Kuo et. al 2004)

  21. A Schematic diagram of the circulation and the vertical motion/ trajectory at mature stage of vortex (0750UTC)

  22. Conclusions • The formation and evolution of themesovorices in QLCS#1 depends greatly on the preexisting boundary, in addition to the vertical wind shear and CAPE. • Contrary to previously documented MCV in QLCS which often accentuated by Coriolis force, this study provides an evidence that the small scale mesovorices originating in the convective region can merge and grow upscale to result in a vortex of greater horizontal and vertical extent through an efficient merger process. • The MCV at the mature stage exhibited some features of balanced vortex, which may induce a new updraft and contribute the following convection.

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