摘要
生成于东部平原地区的江淮切变线和西部青藏高原地区的高原切变线,都处在东亚副热带相同纬度带上。为深化对地形高度迥异的江淮切变线和高原切变线的认识与理解,基于ERA-interim再分析资料和合成分析方法,从切变线与暴雨关系、切变线三维结构特征、切变线附近风场与环流特征以及切变线结构演变中的热力机制等方面对二者进行对比研究。结果表明:(1)江淮切变线分为暖切变线、冷切变线、准静止切变线和低涡切变线4类,高原切变线分为高原横切变线和高原竖切变线2类。江淮切变线与高原切变线均与暴雨关系密切,夏季,有近70%的江淮切变线会产生暴雨,暖切变线暴雨对江淮地区切变线暴雨的雨量贡献最大,低涡切变线暴雨的降水强度最大但发生频率较低;近60%的高原横切变线给高原主体地区带来暴雨,超过55%的竖切变线造成高原东侧及其邻近地区暴雨。(2)江淮切变线与高原切变线均为边界层系统,特征层次分别位于850 hPa和500 hPa。时空尺度上,江淮冷切变线和高原横切变线水平尺度分别可达1000 km和2000 km,垂直伸展厚度分别可达5 km和2 km,生命期分别可达48 h和96 h;江淮切变线和高原横切变线在垂直方向上均有从低到高向北倾斜的特征。(3)江淮冷切变线与高原横切变线风场与环流特征存在差异,江淮冷切变线北侧为东北风,南侧为西南风;高原横切变线东、西两段风场有所不同,其西段类似于江淮冷切变线,东段在不同发展阶段风场有明显变化。(4)江淮冷切变线与高原横切变线的动力结构和热力结构存在差异。动力结构上,二者均位于正涡度带内,正涡度中心强度都在强盛阶段达到最大。热力结构上,江淮冷切变线附近低空锋区特征明显,其西段位于暖湿区内,东段位于干冷区内;高原横切变线南侧具有明显的高温、高湿特征,切变线北侧存在锋区结构。(5)切变线附近的大气非绝热加热与高原横切变线和江淮冷切变线演变关系密切,垂直非均匀加热作用是高原横切变线和江淮冷切变线发展增强最为重要的因子。二者热力结构有差异,减弱机制不同,干冷空气的侵入会导致高原横切变线强度减弱甚至消亡,江淮冷切变线的强度减弱则与南方暖湿空气的向北侵入有关。
The Yangtze-Huaihe shear lines(YHSLs)generated in the eastern plain and the Tibetan Plateau shear lines(TPSLs)generated in the western Tibetan Plateau are located in the same latitude zone of subtropical East Asia.In order to deepen the understanding of the YHSLs and the TPSLs located at different terrain heights,based on the ERA-interim reanalysis data and composite analysis,a comparative study is carried out on the relationship between shear lines and rainstorms,three-dimensional structural characteristics of shear lines,characteristics of wind field and circulation near shear lines,and the thermal mechanism in the structural evolution of shear lines.The results show that:(1)The YHSLs can be divided into four types,namely warm type,cold type,quasi-stationary type and vortex type.The TPSLs are classified into horizontal TPSLs and vertical TPSLs.Both of them are closely related to rainstorms.In summer,nearly 70%of the YHSLs can produce rainstorms.Warm YHSL-induced rainstorms have the largest contribution to total rainfall of YHSL-induced rainstorms,while the vortex YHSL-induced rainstorms have the largest rainfall intensity but low occurrence frequency.Nearly 60%of the horizontal TPSLs bring rainstorms to the main area of the Tibetan Plateau,and more than 55%of the vertical TPSLs cause rainstorms to the east side of the Tibetan Plateau and its adjacent areas.(2)Both the YHSLs and the TPSLs are boundary-layer systems,and the characteristic levels are located at 850 hPa and 500 hPa,respectively.On the temporal and spatial scales,the horizontal dimensions of cold YHSLs and horizontal TPSLs can reach 1000 km and 2000 km,their vertical extension thicknesses can reach 5 km and 2 km,and their life spans can be up to 48 h and 96 h,respectively.Both of the YHSLs and TPSLs are inclined northward from lower to upper levels.(3)There are differences in wind field and circulation characteristics between cold YHSLs and horizontal TPSLs.The north side of a cold YHSL is northeasterly wind,and the south side is southwesterly wind;wind fields in the east and west of a horizontal TPSL are different as the west section is similar to cold YHSL and the east section varies significantly in different development stages.(4)There are differences in dynamic and thermal structures between cold YHSLs and horizontal TPSLs.In terms of dynamic structure,the YHSLs and horizontal TPSLs are all located in the positive vorticity zone,and the strength of the positive vorticity center reaches the maximum at the strong stage.In terms of thermal structure,a cold YHSL is near the low-level frontal zone,its western section is located in the warm and humid zone and its eastern sections is located in the dry and cold zone.The south side of a horizontal TPSL is highly warm and humid,and there is a frontal zone structure on the north side of the TPSL.(5)The diabatic heating near the shear line is closely related to the evolution of the cold YHSL and the horizontal TPSL.The vertical diabatic heating is the most important factor that causes the development and enhancement of the cold YHSL and the horizontal TPSL.There are differences in thermal structure and weakening mechanism between cold YHSLs and horizontal TPSLs.The invasion of dry and cold air will lead to the weakening or even extinction of a horizontal TPSL,while the weakening of the intensity of a cold YHSL is related to the northward invasion of warm and humid air from the south.
作者
姚秀萍
张霞
马嘉理
闫丽朱
张硕
YAO Xiuping;ZHANG Xia;MA Jiali;YAN Lizhu;ZHANG Shuo(China Meteorological Administration Training Centre,Beijing 100081,China;State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences,Beijing 100081,China;Henan Provincial Meteorological Observatory,Zhengzhou 450003,China;University of Chinese Academy of Sciences,Beijing 100049,China;Henan Meteorological Service Center,Zhengzhou 450003,China;Beijing Institute of Applied Meteorology,Beijing 100029,China)
出处
《气象学报》
CAS
CSCD
北大核心
2022年第4期604-617,共14页
Acta Meteorologica Sinica
基金
灾害天气国家重点实验室开放课题(2021LASW-B17)
国家自然科学基金项目(42030611、91937301)
第二次青藏高原综合科学考察研究项目(2019QZKK0105)。
关键词
江淮切变线
高原切变线
结构特征
非绝热加热
异同性
Yangtze-Huaihe shear line
Tibetan Plateau shear line
Structural characteristics
Diabatic heating
Similarities and differences
