1005号热带气旋“乌鲁伊”移动路径分析

Analysis of the tracks of the 1005 tropical cyclone Ului

利用欧洲格点资料,应用天气学方法,从环流场演变、β效应、不对称结构等方面对1005号热带气旋"乌鲁伊"活动过程进行了分析,探讨了"乌鲁伊"不同阶段路径变化的原因.结果表明,澳大利亚大陆高压维持稳定以及热带气旋"托马斯"与"乌鲁伊"之间的相互作用是"乌鲁伊"西行北抬的根本原因.在"乌鲁伊"台风西行过程中,中高纬度环流场进行强烈调整是引起"乌鲁伊"移动路径南翘西折的关键,大陆高压在低纬向"乌鲁伊"北侧嵌入、以及地面气压场上从北指向南的气压梯度力突然增强,对热带气旋"乌鲁伊"移动路径南翘有直接影响.对西风指数的分析表明,"乌鲁伊"的南翘过程与西风指数从最低值484.4 m2/s2向644.3 m2/s2升高过程相对应,"乌鲁伊"移动路径西折与西风指数维持在644.3 m2/s2以上有关.500 hPa位势高度梯度场分析表明,热带气旋"乌鲁伊"从东向西、向南、向西南稳定移动过程中,东南侧和西北侧等梯度线中心数值的差值几乎为0,呈现出对称分布的特点;在热带气旋"乌鲁伊"南翘、西折时,东南侧与西北侧等梯度线数值发生显著变化,南翘时差值为-16.6 m/s2,西折时差值则为12.0 m/s2.500 hPa位势高度梯度场的变化对"乌鲁伊"南翘西折路径具有很好的预示作用.

The developing process of cyclone Ului was studied with respect to its circulation evolution, β effect and asymmetric structure etc, using the European grid data. It＇ s found that the continuous stability of Australian conti- nental high and the interaction between cyclone Tomas and Ului were foundamental causes led to the westbound andnorthward track of Ului. Besides, the strong transition of middle-high latitude atmospheric circulation was a key factor contributing to its southward and westbound track, and the continental high at low latitudes embedded in the north of the cyclone which causes a sudden increase of air pressure gradient force on the ground made a direct im- pact on the southward track of Ului. Analysis of Westerly Wind Index （WWI） indicated that the southward track of Ului corresponded with the increase of WWI from 484.4 mZ/sZto 644.3 m2/s2, and its westbound track was related to the WWI which stabilized around 644.3 m2/s2. Moreover, when Ului moved stably to the west, south and south- west, the southeast and northwest side value of 500 hPa geopotential height gradient difference were about zero, ex- hibiting symmetrical distribution; however, at the southward time the value was -16.6 m/s2 and at westbound time the value was 12.0 m/s2, exhibiting remarkable difference. It＇ s concluded that the change of 500hPa geopo- tential heizht gradient was a good indication to southward and westbound track of Ului.