中尺度数值模式对1996年热带风暴TOM转变温带气旋过程的特征分析
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摘要
在海洋气象导航实际业务中，转向北上进入中高纬度的减弱台风，往往意想不到地突然加强，造成海上风暴的强度往往超过了强台风的强度，对海上航行船只的安全构成了巨大的威胁，而这种海上突发灾害性系统在实际业务预报中又往往容易被预报员所忽视。本文意在通过中尺度模式MM5(V3-2版)对发生在西北太平洋1996年热带风暴TOM转变温带气旋变性过程的模拟，对其发生及演变过程进行三维热力和动力的结构分析。分析结果表明：(1)热带风暴(TOM)在进入中高纬度斜压带时，先是在850hPa高度上有来自风暴西北侧的冷空气侵蚀风暴的暖心结构，但并没有完全破坏风暴低层的暖性特征。只有当热带风暴TOM与500hPa西风槽完全结合并相互作用时，西风槽后的冷空气完全侵入风暴的暖心，并自上而下改变其原有的暖性特征，使其转变为温带气旋。(2)风暴北侧的垂直风切变有利于风暴从正压结构向斜压结构的转变。(3)变性后的温带气旋暖锋锋生较冷锋锋生更为显著。(4)风暴完全并入西风槽后，变性后的温带气旋再次加强与平流层高位涡的向下输送有关。(5)造成风暴东北侧强对流天气主要是由于来自风暴东北侧低层的冷空气与来自风暴西南侧的暖湿气流在风暴的东北侧相会，产生了对流不稳定所引起。(6)通过对模式模拟结果与IR—tbb云图的比较可以看到，中尺度模式对风暴的路径及降水的模拟与实况具有较好的一致性，但是在强度方面与大多数模式一样较实况为弱，尤其是低层的水平风速与实际情况存在着较大差异。尽管如此，模式的模拟结果仍然很好地反映了热带风暴(TOM)减弱后的再加强过程，揭示了热带风暴转变为温带气旋的三维热力及动力的特征结构。
In the operational work of meteorological guidance for oceanic navigation, downgraded typhoons entering mid or high latitude, sometimes re-intensify unexpectedly, with intensity up to severe typhoon, and bring great threat to oceanic shipping. This sudden and unexpected occurrence is sometimes ignored by forecasters. By using MM5(V3-2), the transformation of TOM (a tropical storm in 1996 in Northwestern Pacific Ocean) from tropical storm to extratropical cyclone is simulated, also, the thermodynamic and dynamic structures are analyzed during Tom's evolution. The result shows that: 1) When tropical storm TOM entered mid-high latitude of baroclinic zone, cold air in 850hPa began to erode TOM's warm core, without changing its warm feature in low level. Only when TOM coupled with 500hPa westerly trough and interacted each other, the cold air after the trough destructed completely the warm core, changing the previous warm feather from up to low level, and made it become a extratropical cyclone. 2) Vertical wind s
hear in the storm's northern part was favorable for the transformation from barotropical to baroclinic structure.
3) Extratropical cyclone's warm frontal genesis was more significant than that of cold front.
4) After storm's entering westerly trough, the subtropical cyclone's reintensification was related to the high potential vortex's downward transmission from stratosphere. 5) The main reason for severe convection in storm's northeastern part was the convergence and interactivity between cold air from northeastern part in low level and warm air from southwestern part, this brings about convective instability. 6) Through comparison of MM5's output and IR-TBB, MM5 may gave a satisfactory simulation about storm's track and precipitation, however, as most model, the intensity simulation was weaker than observation, especially the horizontal wind field in low level. Anyway, the model still showed the re-intensification process after TOM's downgrade from tropical storm to extratropical cyclone, demonstrating the 3 dimensional thermodynamic and dynamic structure characteristics during TOM's transformation.
In the operational work of meteorological guidance for oceanic navigation, downgraded typhoons entering mid or high latitude, sometimes re-intensify unexpectedly, with intensity up to severe typhoon, and bring great threat to oceanic shipping. This sudden and unexpected occurrence is sometimes ignored by forecasters. By using MM5(V3-2), the transformation of TOM (a tropical storm in 1996 in Northwestern Pacific Ocean) from tropical storm to extratropical cyclone is simulated, also, the thermodynamic and dynamic structures are analyzed during Tom's evolution. The result shows that: 1) When tropical storm TOM entered mid-high latitude of baroclinic zone, cold air in 850hPa began to erode TOM's warm core, without changing its warm feature in low level. Only when TOM coupled with 500hPa westerly trough and interacted each other, the cold air after the trough destructed completely the warm core, changing the previous warm feather from up to low level, and made it become a extratropical cyclone. 2) Vertical wind s
hear in the storm's northern part was favorable for the transformation from barotropical to baroclinic structure.
3) Extratropical cyclone's warm frontal genesis was more significant than that of cold front.
4) After storm's entering westerly trough, the subtropical cyclone's reintensification was related to the high potential vortex's downward transmission from stratosphere. 5) The main reason for severe convection in storm's northeastern part was the convergence and interactivity between cold air from northeastern part in low level and warm air from southwestern part, this brings about convective instability. 6) Through comparison of MM5's output and IR-TBB, MM5 may gave a satisfactory simulation about storm's track and precipitation, however, as most model, the intensity simulation was weaker than observation, especially the horizontal wind field in low level. Anyway, the model still showed the re-intensification process after TOM's downgrade from tropical storm to extratropical cyclone, demonstrating the 3 dimensional thermodynamic and dynamic structure characteristics during TOM's transformation.
引文
1. Peter M. Klein, Patrick A. Harr, and Russell L. Elsberry, 2000, Extratropical Transition of Western North Pacific Tropical Cyclones: An Overview and Conceptual Model of the Transformation Stage, Wea. Forecasting, vol. 15, 373-395
2． 中国气象局，热带气旋年鉴，气象出版社，1996
3． 亢迪、陈联寿、徐祥德，热带气旋变性的结构特征和能量分析，85-906-07课题组，台风科学、业务试验和天气动力学理论的研究，第三分册，59-61
4． 徐祥德，台风变性对台风强度突变影响的研究，85-906-07课题组，台风科学、业务试验和天气动力学理论的研究，第三分册，58-59
5． 王国民、王诗文、李建军，一个人造台风方案及其在移动套网络模式中的应用，热带气象学报，1996，12(1)，9-17
6． 蔡义勇，台风暴雨相当位涡诊断分析，气象学报，50(1)，118-125
7. Geoffrey J. DiMego, and Lance F.Bosart, 1982, The Transformation of Tropical Storm Agnes into an Extratropical Cyclone, Part I: The Observed Fields and Vertical Motion Computations, Mon. Wea. Rev., vol.110, 385-410
8. Mark R. Sinclair, 1993, A Diagnostic Study of the Extratropical Precipitation Resulting from Tropical Cyclone Bola, Mon. Wea. Rev., vol.121,2690-2707
9. Ying-Hwa Kuo, and Richard J.Reed, 1988, Numerical Simulation of an Explosively Deepening Cyclone in the Eastern Pacific, Mon. Wea. Rev., vol.l16, 2081-2105
10. Han-Ru Cho, 1993, A Mechanism Causing Mesoscale Organizations of Precipitation in Midlatitude Cyclones, J. Meteorol. Appl. ,vol.32, 155-160
11. Robert E. Hart, and Jenni L. Evans, 2001, A Climatology of the Extratropical Transition of Atlantic Tropical Cyclones, J. Climate., vol. 14, 546-563
12. K. A. Browning, G Vaughan, and P. Panagi, 1998, Analysis of an ex-tropical cyclone after its reintensification as a warm-core extratropical cyclone, Q. J. R. Met. Sec., vol.124, 2329-2356
13． 林明智，刘有奇，9617台风TOM演变为温带气旋特征分析，气象科技，1997，4，55-59
14． 蔡则怡，7503号台风环流维持和特大暴雨持续的物理机制，暴雨、灾害，气象出版社，1998．10
15． 励申申等，台风倒槽暴雨的动力结构，台风会议文集，气象出版社，1985
16． 钱自强、张德，上海地区台风倒槽暴雨分析，大气科学，vol．9(4)，400-405，1985
17． 励申申、寿绍文等，登陆台风与外围暴雨的相互作用，气象学报，vol．50(1)，1992
18． 张兴强、何金海等，非纬向高空急流与远距离台风中尺度暴雨研究，2000
19. Davis, C. A., and K. A. Emanuel, 1991, Potential vorticity diagnostics of cyclogenesis, Mon. Wea. Rev., vol.119, 1929-1953
20. Foley, G. R., and B. N. Hanstrum, 1994, The capure od tropical cyclones by cold fronts off the west coast of Australia, Wea. Forecasting, vol.9, 577-592
20. 21. McTaggart-Cowan, R., J. R. Gyakum, and M. K. Yau, 2001, Sensitivity testing of extratropical transitions using potential vorticity inversions to modify initial conditions: Hurricane Earl case study. Mon. Wea. Rev., vol.129, 1617-1636
21. Palmen, E., 1958, Vertical circulation and release of kinetic energy during the development of Hurricane Hazel into an extratropical cyclone. Tellus, vel.10, 1-23.
22. Shapiro, M. A, and D. Keyser, 1990, Fronts; jet streams and the tropopause. Extratropical Cyclones, the Erik Palmen memorial volume, C. W. Newton and E. O.
Holopainen Eds., Amer. Meteor. Soc., 167-191
23. Browning., K. A., 1997, The dry intrusion perspective of extratropical cyclone development. Meteorol. Appl., vol.4, 229-234
24. Harr, P.A., and R.L.Elsberry, 2000: Extratropical transition of tropical cyclones over the western North Pacific. Part Ⅰ: Evolution of structural characteristics during the transition process. Mon. Wea. Rev., 128, 2613-2633
25. Harr, P.A., R.L.Elsberry, and T. F. Hogan, 2000: Extratropical transition of tropical cyclones over the western North Pacific. Part Ⅱ: Evolution of structural characteristics during the transition process. Mon. Wea. Rev., 128, 2634-2653
26． 陈渭民、夏浣清、陈光宇，卫星气象学，气象出版社，1989
27． 寿绍文，中尺度天气动力学，气象出版社，1993
28． 丁一汇，中尺度天气和动力学研究，气象出版社，1996
29． 朱乾根等，天气学原理和方法，气象出版社，1983
2． 中国气象局，热带气旋年鉴，气象出版社，1996
3． 亢迪、陈联寿、徐祥德，热带气旋变性的结构特征和能量分析，85-906-07课题组，台风科学、业务试验和天气动力学理论的研究，第三分册，59-61
4． 徐祥德，台风变性对台风强度突变影响的研究，85-906-07课题组，台风科学、业务试验和天气动力学理论的研究，第三分册，58-59
5． 王国民、王诗文、李建军，一个人造台风方案及其在移动套网络模式中的应用，热带气象学报，1996，12(1)，9-17
6． 蔡义勇，台风暴雨相当位涡诊断分析，气象学报，50(1)，118-125
7. Geoffrey J. DiMego, and Lance F.Bosart, 1982, The Transformation of Tropical Storm Agnes into an Extratropical Cyclone, Part I: The Observed Fields and Vertical Motion Computations, Mon. Wea. Rev., vol.110, 385-410
8. Mark R. Sinclair, 1993, A Diagnostic Study of the Extratropical Precipitation Resulting from Tropical Cyclone Bola, Mon. Wea. Rev., vol.121,2690-2707
9. Ying-Hwa Kuo, and Richard J.Reed, 1988, Numerical Simulation of an Explosively Deepening Cyclone in the Eastern Pacific, Mon. Wea. Rev., vol.l16, 2081-2105
10. Han-Ru Cho, 1993, A Mechanism Causing Mesoscale Organizations of Precipitation in Midlatitude Cyclones, J. Meteorol. Appl. ,vol.32, 155-160
11. Robert E. Hart, and Jenni L. Evans, 2001, A Climatology of the Extratropical Transition of Atlantic Tropical Cyclones, J. Climate., vol. 14, 546-563
12. K. A. Browning, G Vaughan, and P. Panagi, 1998, Analysis of an ex-tropical cyclone after its reintensification as a warm-core extratropical cyclone, Q. J. R. Met. Sec., vol.124, 2329-2356
13． 林明智，刘有奇，9617台风TOM演变为温带气旋特征分析，气象科技，1997，4，55-59
14． 蔡则怡，7503号台风环流维持和特大暴雨持续的物理机制，暴雨、灾害，气象出版社，1998．10
15． 励申申等，台风倒槽暴雨的动力结构，台风会议文集，气象出版社，1985
16． 钱自强、张德，上海地区台风倒槽暴雨分析，大气科学，vol．9(4)，400-405，1985
17． 励申申、寿绍文等，登陆台风与外围暴雨的相互作用，气象学报，vol．50(1)，1992
18． 张兴强、何金海等，非纬向高空急流与远距离台风中尺度暴雨研究，2000
19. Davis, C. A., and K. A. Emanuel, 1991, Potential vorticity diagnostics of cyclogenesis, Mon. Wea. Rev., vol.119, 1929-1953
20. Foley, G. R., and B. N. Hanstrum, 1994, The capure od tropical cyclones by cold fronts off the west coast of Australia, Wea. Forecasting, vol.9, 577-592
20. 21. McTaggart-Cowan, R., J. R. Gyakum, and M. K. Yau, 2001, Sensitivity testing of extratropical transitions using potential vorticity inversions to modify initial conditions: Hurricane Earl case study. Mon. Wea. Rev., vol.129, 1617-1636
21. Palmen, E., 1958, Vertical circulation and release of kinetic energy during the development of Hurricane Hazel into an extratropical cyclone. Tellus, vel.10, 1-23.
22. Shapiro, M. A, and D. Keyser, 1990, Fronts; jet streams and the tropopause. Extratropical Cyclones, the Erik Palmen memorial volume, C. W. Newton and E. O.
Holopainen Eds., Amer. Meteor. Soc., 167-191
23. Browning., K. A., 1997, The dry intrusion perspective of extratropical cyclone development. Meteorol. Appl., vol.4, 229-234
24. Harr, P.A., and R.L.Elsberry, 2000: Extratropical transition of tropical cyclones over the western North Pacific. Part Ⅰ: Evolution of structural characteristics during the transition process. Mon. Wea. Rev., 128, 2613-2633
25. Harr, P.A., R.L.Elsberry, and T. F. Hogan, 2000: Extratropical transition of tropical cyclones over the western North Pacific. Part Ⅱ: Evolution of structural characteristics during the transition process. Mon. Wea. Rev., 128, 2634-2653
26． 陈渭民、夏浣清、陈光宇，卫星气象学，气象出版社，1989
27． 寿绍文，中尺度天气动力学，气象出版社，1993
28． 丁一汇，中尺度天气和动力学研究，气象出版社，1996
29． 朱乾根等，天气学原理和方法，气象出版社，1983