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气象:2020,46(8):1053-1064
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山东省线状中尺度对流系统的天气学特征
侯淑梅,孙晶,郑怡,韩永清
(山东省气象台,济南 250031)
Synoptic Characteristics of Linear Mesoscale Convective System in Shandong Province
HOU Shumei,SUN Jing,ZHENG Yi,HAN Yongqing
(Shandong Meteorological Observatory, Jinan 250031)
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投稿时间:2019-05-20    修订日期:2020-06-19
中文摘要: 按照如下标准确定一个线状中尺度对流系统(linear mesoscale convective system,LMCS):40 dBz以上反射率因子连续或准连续回波带尺度≥100 km并持续至少1 h,镶嵌着40 dBz回波的35 dBz回波要求严格连续,线状或准线状的对流区域拥有一个共同的前边缘,最大回波强度≥50 dBz。从2012—2016年雷达资料中挑选出27个影响山东的LMCS,分析其天气学特征。结果表明:影响山东的LMCS 8月出现次数最多,形成时间集中在傍晚到前半夜,生命史一般为1~2 h,大多数具有后向传播特征;形成LMCS的初始对流单体绝大多数位于河北省,单体生成后一般向东偏南方向移动;LMCS大多数是东北—西南向,尺度一般介于100~200 km。文章提炼了形成LMCS的后倾槽、前倾槽和冷涡等三类天气学模型。850 hPa伴有暖温度脊或暖中心是形成LMCS的一个重要特征,冷涡和前倾槽类500 hPa中空急流以及后倾槽类700 hPa以下低空急流在形成LMCS中起着重要作用。当850 hPa比湿>8 g·kg-1,沙氏指数和抬升指数均为负值时,可能出现LMCS。若对流有效位能>1 〖KG-*5〗000 J·kg-1,对流抑制较小,且850 hPa与500 hPa气温差大于25℃,出现LMCS的概率达80%。LMCS出现时均伴有短时强降水,70.4%的LMCS造成雷暴大风、冰雹或强降水灾害。冰雹和大风比短时强降水需要大气层结的不稳定度更高,仅有短时强降水出现时,0℃层和-20℃层的高度明显比冰雹和大风出现时的高度高。
Abstract:The synoptic characteristics of LMCS (linear mesoscale convective system) were analyzed based on 27 selected LMCSs affecting Shandong from the 2012-2016 radar data. The filter conditions are as below: the contiguous or quasi-contiguous echo band larger than 40 dBz is over 100 km and lasts for at least 1 h, the 35 dBz echo embedded with the 40 dBz echo is strictly contiguous, the linear or quasi-linear convection area shares a common leading edge, and the maximum echo intensity is over 50 dBz. The characteristics of the study are concluded as follows. The LMCS affected Shandong has a high frequency in August, and the formation time is concentrated in the dusk to the first half of the night, lifespan is generally 1-2 h, and most of them have characteristics of backward propagation. Most of the initial convective cells are generated in Hebei and generally move eastward by southward. Most of the LMCSs are in a northeast-southwest trend, and the scale is between 100 and 200 km. Three types of synoptic models of LMCS formation are constructed, including forward-tilting trough, backward-tilting trough and cold vortex. The warm temperature ridge or warm center at 850 hPa is the important feature of LMCS formation. The mid-level jet stream at 500 hPa in cold vortex and forward-tilting trough category, and the low-level jet stream below 700 hPa in backward-tilting trough category all play very important roles in the LMCS formation. LMCS constantly occurs when 850 hPa specific humidity is greater than 8 g·kg-1 and the Lift Index (LI) and Showalter Index (SI) are both negative. The probability of LMCS occurrence is up to 80% when T850-500 >25℃ and CAPE >1 〖KG-*5〗000 J·kg-1 with small CIN. When LMCS appears, it is usually accompanied by short-duration heavy precipitation, 70.4% LMCS contributes to disasters of thunderstorm gale, hail and severe precipitation. The hail and gale require higher stratification instability than short-duration severe precipitation. When only the short-duration heavy precipitation occurs, the heights of 0℃ and -20℃ layers are significantly higher than those when hail and gale occur.
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基金项目:山东省自然科学基金项目(ZR2016DM20)、中国气象局预报员专项(CMAYBY2018-041)和山东省气象局课题(2016sdqxz01、2014sdqxm21)共同资助
引用文本:
侯淑梅,孙晶,郑怡,韩永清,2020.山东省线状中尺度对流系统的天气学特征[J].气象,46(8):1053-1064.
HOU Shumei,SUN Jing,ZHENG Yi,HAN Yongqing,2020.Synoptic Characteristics of Linear Mesoscale Convective System in Shandong Province[J].Meteor Mon,46(8):1053-1064.