doi:  10.3878/j.issn.1006-9895.1807.18147
高原涡、西南涡影响的两次四川暴雨过程的对比分析

Comparative Analysis of two Rainstorm Processes in Sichuan Province affected by Tibetan Plateau Vortex and Southwest Vortex
摘要点击 117  全文点击 41  投稿时间:2018-04-09  修订日期:2018-07-17
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基金:  国家自然科学基金资助项目(41661144024、41475054、41475097);高原大气与环境四川省重点实验室开放课题(PAEKL-2017-K2),国家自然科学基金
中文关键词:  高原涡  西南涡 四川盆地暴雨  对比分析 MCC 水汽源
英文关键词:  plateau  vortex, southwest  vortex, rainstorms  in Sichuan  basin, comparative  analysis, MCC, moisture  source
     
作者中文名作者英文名单位
周玉淑ZHOU Yushu中国科学院大学地球科学学院;中国科学院大气物理研究所云降水物理与强风暴重点实验室LACS
颜玲YAN Ling南京信息工程大学气象灾害教育部重点实验室/气候与环境变化国际合作联合实验室/气象灾害预报预警与评估协同创新中心
引用:周玉淑,颜玲.2019.高原涡、西南涡影响的两次四川暴雨过程的对比分析[J].大气科学
Citation:ZHOU Yushu,YAN Ling.2019.Comparative Analysis of two Rainstorm Processes in Sichuan Province affected by Tibetan Plateau Vortex and Southwest Vortex[J].Chinese Journal of Atmospheric Sciences (in Chinese)
中文摘要:
      为了进一步研究高原涡、西南涡对西南暴雨的影响,本文用中国气象局自动站与CMORPH融合的逐时降水资料、国家卫星气象中心的逐时FY-2E的云顶亮温TBB资料、欧洲气象资料中心(ERA-interim)的再分析资料,通过天气学诊断分析方法以及拉格朗日轨迹模式HYSPLIT v4.9,对发生在四川盆地的有高原涡东移影响西南涡发展引发暴雨的两次过程进行对比分析,发现:1)两次暴雨过程的降水强度和分布有明显区别,并且TBB活动特征显示在过程一中有MCC的产生和发展,过程二则没有;2)对于过程一,500hPa上,高原涡逐渐减弱为高原槽并伸展到四川盆地上空,850hPa上,在鞍型场附近有MCC的产生和发展,200hPa上,高原涡在南亚高压北部偏西风急流下方的强辐散区内,西南涡位于南亚高压东南侧急流区下空稳定少动,偏东风急流北部有辐散中心,有利于西南涡的加强。对于过程二,500hPa高原涡东移在四川盆地上空与西南涡耦合,形成一个稳定且深厚的系统,200hPa上,四川盆地始终位于南亚高压东侧的西北气流中,“抽吸作用”明显;3)在过程一中,位涡逐渐东传且位涡增加的地方对应强降水区与MCC爆发区,反映了暴雨和位涡的发展基本一致。在过程二中,中层位涡高值区从高原上东移并下传至盆地上空,两涡耦合使得上下层打通,位涡值比耦合之前单独的两涡强度更强,另一方面,本文也应证了二阶位涡的水平分布与暴雨落区有较好的对应关系;MCC产生的必要条件是中层大气要有强正涡度、强辐合和强上升运动,在未产生MCC前,过程一与过程二在盆地上空的动力条件甚至是相反的;从热力条件看,过程一中有明显的干冷空气入侵,增强不稳定条件,有利于MCC的产生并引发强降水;5)通过拉格朗日方法的水汽轨迹追踪模式和聚类分析方法得到,过程一主要有两条水汽通道,通道一来自阿拉伯海和孟加拉湾洋面的底层,通道二来自四川南部750m以下高度;而过程二的主要水汽输送通道有三条,通道一来自西方地中海、黑海和里海上空1500m~2500m高度附近,通道二来自阿拉伯海和印度洋的底层,通道三的水汽从孟加拉湾低层绕过云贵高原直接输送到四川盆地。
Abstract:
      This paper makes some comparative analysis of two rainstorm processes in Sichuan province affected by the Tibetan Plateau Vortex and Southwest Vortex, based on the reanalysis data from ECMWF ERA-Interim, CMORPH data(which is derived from station observations and satellite retrievals of precipitation), the hourly?cloud?top?TBB(black body temperature)?data of?FY-2E and Lagrangian trajectory model HYSPLIT v4.9, and the main results are as follows: 1) The intensity and distribution of precipitation were significantly different in the two heavy rain processes, and the characteristics of mesoscale convective cloud system showed that MCC was stimulated in process one, but not found in process two; 2) During process one, At 500hPa, the Tibetan Plateau Vortex gradually faded into a plateau trough and spread over the Sichuan Basin. At 850hPa, MCC was induced near the wind convergence zone. At 200hPa, the Southwest Vortex was located in the southeast of South Asia High, showing an area of rapid flow and strong divergence, which contributes to the intensification of Southwest Vortex. But for the second process, the Tibetan Plateau Vortex has gradually coupled with the Southwest Vortex , resulting to a stable and deep system. At 200 hPa, a distinct pumping effect can be found over the Sichuan Basin since it was always located below the northwestern stream of South Asian High; 3) During process one, PV(potential vortex) has gradually spread to the east and the area where PV increases corresponds to the strong precipitation area and the outburst area of MCC, which reflects of a basic consistence between the development of rainstorm and PV. Besides, in the second process, the high value zone of PV in mid-level moves eastward from the plateau and the high PV is transmitted down to the basin. The coupling of two vortices makes the PV value lager than each single vortex. Also, this article has proved a good relationship between the distribution of anomaly second-order PV and heavy rain; 4) The main difference between the two processes is the stimulation of MCC, which calls for a necessary atmospheric condition with strong positive vorticity, strong convergence and strong ascending movements. And the dynamic conditions in the two rainstorm processes may be opposite before the formation of MCC. From the thermodynamic perspective, there is an invasion of dry and cold air in process one, and the large gradient of potential pseudo-equivalent?temperature benefits to stimulate the mesoscale convective system and cause heavy rain; 5) According to the Lagrangian trajectory model and clustering analysis method, there are two water vapor channels in process one: The first channel is from the bottom layer of the Arabian Sea and the Bay of Bengal, while the second channel is from the south of Sichuan in height of 750 m. In the second process, there are three main vapor transport channels. Channel 1 is from the Western Mediterranean, Black Sea and Liberia in level of 1500m to 2500m. Channel 2 is from the bottom of the Arabian Sea and the Indian Ocean. Water vapor of channel 3 is directly transported to the Sichuan Basin from the bottom of the Bay of Bengal, passing by the Yunnan-Guizhou Plateau.
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