准平直长路径与多折向路径东移高原涡的环境场特征  

The ambient field characteristics for quasi-straight long path and multi-turning path of eastward moving Tibetan Plateau vortex

作　　者：郁淑华[1,2] 高文良 彭骏[1,2] YU Shuhua;GAO Wenliang;PENG Jun(Institute of Plateau Meteorology,China Meteorological Administration,Chengdu 610072,China;Sichuan Provincial Key Laboratory of Heavy Rain,Drought and Flood Disasters in Plateau and Basin,Chengdu 610072,China;Ya'an Meteorological Office of Sichuan Province,Ya'an 625000,China)

机构地区：[1]中国气象局成都高原气象研究所,成都610072 [2]高原与盆地暴雨旱涝灾害四川省重点实验室,成都610072 [3]四川省雅安市气象局,雅安625000

出　　处：《气象学报》2022年第6期864-877,共14页Acta Meteorologica Sinica

基　　金：国家自然科学基金项目(91937301)。

摘　　要：利用1998—2018年NCEP/NCAR全球最终分析数据、大气观测资料、青藏高原低涡切变线年鉴,采用合成方法分析了准平直长路径和多折向路径东移高原低涡的环境场特征,探讨了低涡折向的主导因素。结果表明:准平直长路径低涡、多折向路径低涡长时间活动的共同环境场特征是有明显影响低涡活动的天气系统,副热带高压(简称副高)位于高原低涡东南方,高原低涡以北上空伴有东、西段急流;低涡有正涡度平流输入,高原低涡上空为辐散区,高空高位涡下传到低涡。同时,二者环境场特征存在明显差异,多折向路径低涡伴有较强的热带低压活动,是在副高、西风带天气系统、热带低压相互作用的环流背景下,高原涡东移受阻而折向;准平直长路径低涡是在西风带天气系统为主导的环流背景下向东移动;准平直长路径低涡受冷空气、西南气流与高空锋区的影响比多折向路径低涡强,造成了准平直长路径低涡的正涡度平流、位涡、斜压性、高空辐散比多折向路径低涡强。多折向路径低涡折向的主导因素是环境场条件使低涡在减弱、东移受阻的情况下高空高位涡中心在低涡西部上空,高位涡下传使低涡加强的强正位涡异常区出现在低涡西部,低涡移向低涡加强的区域。Composite methods are applied to analyze atmospheric observations and the NCEP/NCAR Final Operational Global Analysis data as well as the Tibetan Plateau vortex(TPV) and shear line yearbooks from 1998 to 2018 to reveal the ambient field characteristics for the groups of the Tibetan Plateau vortices that move eastward following quasi-straight long-path(QSLTPVs) and multi-turning path(MTTPVs), respectively. The leading factors that lead to the TPVs’ s turning are also discussed. The results show that the ambient field characteristics common for long-lasting QSLTPVs and MTTPVs activities are that there are obvious weather systems affecting TPVs. And the subtropical high is located to the southeast of the TPVs, while the east and west segments of jet stream exist in the upper levels to the north of the TPV. These systems promote positive vorticity advection into the TPVs and there is positive divergence region above the TPVs. Potential vorticity in the upper levels are transported downward to TPVs. The difference in ambient field conditions between the QSLTPVs and the MTTPVs is obvious, too. The MTTPVs are accompanied by strong tropical low-pressure activities. They are blocked and forced to turn under the influences of the sub-tropical high, the westerly wind belt, the topical low-pressure systems and their interaction. The QSLTPVs move eastward in the ambient background field dominated by westerly synoptic systems. And the QSLTPVs are more affected by cold air, southwesterly flow and upper-level front belt than the MTTPVs. These systems lead to stronger positive vorticity advection, larger potential vorticity, stronger baroclinicity and positive divergence in upper levels. The main factors causing the turning of MTTPVs are that the TPVs are weakened and blocked by the ambient field conditions, and the downward transport of high-level potential vorticity to the TPV results in strong positive vorticity in the west of the TPV. Thereby, the TPV moves to the area where it becomes stronger, which explains why the TPV m

关 键 词：青藏高原低涡 准平直东移长路径 多折向路径 环境场特征 位涡诊断 

分 类 号：P447[天文地球—大气科学及气象学]