高级检索
胡素琴, 希热娜依·铁里瓦尔地, 李娜, 等. 2022. 南疆西部干旱区两次极端暴雨过程对比分析[J]. 大气科学, 46(5): 1177−1197. doi: 10.3878/j.issn.1006-9895.2204.22001
引用本文: 胡素琴, 希热娜依·铁里瓦尔地, 李娜, 等. 2022. 南疆西部干旱区两次极端暴雨过程对比分析[J]. 大气科学, 46(5): 1177−1197. doi: 10.3878/j.issn.1006-9895.2204.22001
HU Suqin, Xerinay Tiliwaldi, LI Na, et al. 2022. Comparative Analysis of Two Extreme Rainstormsin the Arid Area of Western South Xinjiang [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 46(5): 1177−1197. doi: 10.3878/j.issn.1006-9895.2204.22001
Citation: HU Suqin, Xerinay Tiliwaldi, LI Na, et al. 2022. Comparative Analysis of Two Extreme Rainstormsin the Arid Area of Western South Xinjiang [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 46(5): 1177−1197. doi: 10.3878/j.issn.1006-9895.2204.22001

南疆西部干旱区两次极端暴雨过程对比分析

Comparative Analysis of Two Extreme Rainstormsin the Arid Area of Western South Xinjiang

  • 摘要: 利用常规气象观测资料、NCEP再分析资料、ERA5分析场数据等资料,对南疆西部两次极端暴雨过程的环境条件和形成机理进行对比分析,以更深入理解南疆极端降水特征和产生机制。两次过程分别发生在春季和夏季,高层环流存在显著差异,南亚高压分别呈东部型和双体型,但配合中层的“阶梯槽”形势,均为极端降水提供了特殊有利的环流背景。低空700~850 hPa偏东急流是南疆西部极端降水发生的重要天气系统,其不但是暴雨发生地主要水汽通道,还与地形形成强烈辐合,是极端降水重要的触发和水汽集中机制。引入二阶湿位涡对两次暴雨过程的非均匀特征及可能产生机制进行了对比分析。结果表明,二阶湿位涡高值区与降水的发展演变呈现较高一致性,二阶湿位涡主分量包含对流稳定度与绝对涡度垂直梯度的耦合,体现极端降水大气的主要动热力结构特点:发生在2021年6月15~16日的夏季过程,极端降水区主要位于昆仑山沿线,与塔里木盆地南侧强烈的低层气旋性旋转有关,旋转促进水汽快速集中,垂直方向表现为中层负涡度叠加于正涡度之上,垂直涡度梯度显著,同时水汽抬升凝结,中层大气加湿加热,对流稳定度在垂直方向非均匀性增强,两种垂直梯度结构均有助于垂直运动增强,促进极端降水形成;发生在2020年4月17~24日的春季过程,降水主要位于南疆西部喇叭口地形区,“阶梯槽”形势造成的越山干冷气流和塔里木盆地的偏东暖湿气流辐合,形成中层正涡度带,激发上升运动,是极端降水的主要成因。

     

    Abstract: This study examines the characteristics of environmental conditions and formation mechanisms of the two extreme rainstorms in the west of southern Xinjiang. Conventional observation data, NCEP reanalysis data, and ERA5 reanalysis data were used to provide a thorough understanding of the occurrence of strong precipitation in this arid area. The two processes occurred in spring and summer with the upper-level circulation presenting quite a different pattern. South Asian highs are located at different latitudes, but both formed favorable configurations with mid-level low troughs for extreme precipitation. The low-level 700–850 hPa easterly jet is one of the most important weather systems for extreme precipitation, transporting moisture, and forming strong convergence with the terrain to trigger the precipitation. The SMPV (second-order moist potential vorticity) quantity was used to diagnose the nonuniform features and the possible generation mechanisms of the two rainstorms. The results indicate that high-value areas of SMPV exhibit high correlations with the evolution of heavy rainstorms by the coupling of convective stability and vertical gradient of absolute vorticity. The process that occurred during 15–16 June 2021 presented extreme precipitation mainly along the Kunlun Mountains, which is associated with the strong low-level cyclonic rotation in the south of the Tarim Basin. This rotation promoted the concentration of water vapor. The vertical gradient of vertical vorticity, which was performed as a superposition of the negative vorticity over positive vorticity, was significant. Meanwhile, the condensation of water vapor during lifting warmed and moistened the mid-level atmosphere with the nonuniformity enhancement of convective stability. Both of these processes contributed to intensifying the upward vertical motion and thus formed extreme precipitation. The process that occurred during 17–24 April 2020 presented strong precipitation in the western trumpet-shaped topography of southern Xinjiang. The dry and cold air flow aroused by the stepped-distributed troughs encountered the easterly warm, moist air flow when crossing the mountain. This formed large vertical vorticity belts and intensified the vertical motions, which was the main mechanism for extreme precipitation.

     

/

返回文章
返回