2018年冬季浙江连续阴雨天气东亚高空急流特征分析

利用欧洲中心ERA 5月平均资料和日资料分析2018年冬季浙江罕见连续阴雨寡照期间东亚高空副热带急流和温带急流的位置和强度特征,分析连阴雨异常天气期间东亚高空急流在位置和强度上的部分异常特征。结果表明:东亚高空急流活动区域以青藏高原上空为分界线,分为南北两支,南支副热带急流活动区域沿青藏高原南侧呈准纬向分布,北支温带急流活动区域呈西北—东南走向,东南方向朝东亚沿海延伸并与高原南侧副热带急流频数集中区交汇,温带急流在蒙古高原贝加尔湖附近存在一个活动频数大值区。浙江连续阴雨期间,东亚副热带高空急流总体上强度偏强、位置偏北,温带急流总体偏弱、位置总体偏南。连续阴雨期间高空急流中心频数多于气候平均,副热带高空急流位置偏北、温带急流位置偏南,急流频数增多造成高(低)层辐散(合)配置与同时期气候态存在差异,垂直上升运动强度更强、范围更广,有利于连阴雨形成。

The Circulation Characteristics of East Asian Upper-Tropospheric Jet on Continuous rainfall in 2018 winter

Based on the ECMWF ERA5 monthly mean data from 1979 to 2019 and daily reanalysis dataset from December 2018 to February 2019, the Circulation Characteristics on East Asian subtropical jet (EASJ) and polar-front jet (EAPJ) are analyzed to realise the anomalous features of them throughout continuous rainfall in 2018 winter.It is demonstrated that the zone of East Asian Upper-Tropospheric Jet (EASJ and EAPJ) have geographical boundary along Tibetan Plateau (TP), on the south of TP is EASJ which is Latitudinal distribution yet the north of TP is EAPJ which is Northwest-Southeast distribution.The distribution of the numbers of jet core extracted by the daily data and the max curvature of wind speed isoline extracted by the monthly mean data both confirm it. It is also indicated that nearby Lake Baikal is a amass area of numbers of EAPJ core, amass area of numbers of EAPJ and EASJ are converged on East Asia coast. Occurred in time of Continuous rainfall, the location of EASJ is northward to its normal position and the EAPJ is southward to its normal position by calculating the position index of jet,the numbers of EAPJ and EASJ core are both more than normal, the intensity of EASJ is increased while EAPJ is decreased.The norther EASJ,souther EAPJ and more numbers of jet core make a better matching for lower convergence and upper divergence, strengthen updraft vertical speed and scope,it profits the continuous rainfall.