江苏近10 a高架雷暴特征分析
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摘要
对2007—2016年发生在江苏地区的冬半年雷暴进行特征分析,筛选出12次典型的高架雷暴天气过程,揭示江苏发生高架雷暴的时空分布特征和典型的环流形势,发现逆温层顶之上的不稳定浅层和上下层强垂直风切变分别为高架雷暴的发生提供弱热力不稳定和强动力不稳定条件。强垂直风切变、850 hPa附近强烈的锋生导致的锋面次级环流,高空槽前正涡度平流随高度增加以及高层辐散、低层辐合造成的抽吸作用,为高架雷暴的发生和维持提供逆温层之上的动力抬升条件。高架雷暴发生时高仰角反射率因子呈现出类似零度层亮带的环形特征,对流单体不断生成在圆环附近。初步归纳了江苏高架雷暴的预报着眼点:500 hPa先后高空槽东移,700 hPa有16 m·s~(-1)以上的西南急流,850 hPa切变线东伸,存在逆温层顶高于1. 5 km,逆温强度大于5℃的较强逆温,0～6 km垂直风切变超过18 m·s~(-1),700 hPa与500 hPa温度差在15℃以上以及700hPa的相对湿度高于80%,且比湿在5～6 g·kg~(-1)。
Based on analysis on the characteristics of thunderstorms in the past decade from 2007 to2016 during winter half year in Jiangsu,twelve typical elevated thunderstorm processes were screened to reveal the temporal and spatial distribution characteristics and the typical circulation situation of elevated thunder storms occurred in Jiangsu. We found that unstable shallow layer on the top of the inversion layer and strong vertical wind shear provided weak thermal instability and strong dynamical instability conditions.Strong vertical wind shear,frontal secondary circulation caused by frontogenesis at 850 hPa,the positive vorticity advection increased with height in front of the upper trough,and the pumping action caused by upper divergence and lower convergence provide dynamical uplift condition above the top of the inversion layer. On higher elevation angle echo present a circle which is like a zero band bright band. Convective monomer appeared constantly around the circle. We summarized forecast points of elevated thunder storms occurred in Jiangsu: two high troughs on 500 hPa move eastward successively; the speed of southwest jet is greater than 16 m·s~(-1) on 700 hPa,shear line on 850 hPa extends towards east; the height of the top of theinversion layer is higher than 1.5 km; the inversion intensity is stronger than 5 ℃; 0—6 km vertical wind shear is stronger than 18 m·s~(-1); temperature contrast of 700 hPa and 500 hPa is bigger than 15 ℃ and relative humidity of 700 hPa is higher than 80%,with its specific humidity at 5—6 g·kg~(-1).
Based on analysis on the characteristics of thunderstorms in the past decade from 2007 to2016 during winter half year in Jiangsu,twelve typical elevated thunderstorm processes were screened to reveal the temporal and spatial distribution characteristics and the typical circulation situation of elevated thunder storms occurred in Jiangsu. We found that unstable shallow layer on the top of the inversion layer and strong vertical wind shear provided weak thermal instability and strong dynamical instability conditions.Strong vertical wind shear,frontal secondary circulation caused by frontogenesis at 850 hPa,the positive vorticity advection increased with height in front of the upper trough,and the pumping action caused by upper divergence and lower convergence provide dynamical uplift condition above the top of the inversion layer. On higher elevation angle echo present a circle which is like a zero band bright band. Convective monomer appeared constantly around the circle. We summarized forecast points of elevated thunder storms occurred in Jiangsu: two high troughs on 500 hPa move eastward successively; the speed of southwest jet is greater than 16 m·s~(-1) on 700 hPa,shear line on 850 hPa extends towards east; the height of the top of theinversion layer is higher than 1.5 km; the inversion intensity is stronger than 5 ℃; 0—6 km vertical wind shear is stronger than 18 m·s~(-1); temperature contrast of 700 hPa and 500 hPa is bigger than 15 ℃ and relative humidity of 700 hPa is higher than 80%,with its specific humidity at 5—6 g·kg~(-1).
引文
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[11]俞小鼎.强对流天气的多普勒天气雷达探测和预警.气象科技进展,2011,1(3):31-41.YU Xiaoding.Detection and warnings of severe convection with Doppler weather radar.Advances in Meteorological Science and Technology(in Chinese),2011,1(3):31-41.
[12]胡鹏,蔡哲,张永靖,等.一次伴有雷暴的暴雪天气成因机理分析.气象科学,2015,35(2):210-215.HU P eng,CAI Zhe,ZHANG Yongjing,et al.Cause analysis on a snowstorm accompanied with thunderstorm.Journal of the Meteorological Sciences(in Chinese),2015,35(2):210-215.
[2]Grant B N.Elevated cold-sector severe thunderstorms:Apreliminary study.Natl.Wea.Dig.,1995,19(4):25-31.
[3]Wilson J W,Roberts R D.Summary of convective storm initiation and evolution during IHOP:Observational and modeling perspective.Mon.Wea.Rev.,2006,134(1):23-47.
[4]Moore J T,Glass F H,Graves C E,et al.The environment of warm-season elevated thunderstorms associated with heavy rainfall over the central United States.Wea.Forecasting,2003,18(5):861-878.
[5]Ostby F P.Improved accuracy in severe storm forecasting by the severe local storms unit during the last 25 years:then versus now.Wea.Forecasting,1999,14(4):526-543.
[6]俞小鼎,周小刚,王秀明.雷暴与强对流临近天气预报技术进展.气象学报,2012,70(3):311-337.YU Xiaoding,ZHOU Xiaogang,WANG Xiuming.The advances in the nowcasting techniques on thunderstorms and severe convection.Acta Meteorologica Sinica(in Chinese),2012,70(3):311-337.
[7]苏德斌,焦热光,吕达仁.一次带有雷电现象的冬季雪暴中尺度探测分析.气象,2012,38(2):204-209.SU Debin,JIAO Reguang,LDaren.Mesoscale observation analysis of a winter snowstorm with thunder and lightning in Beijing Area.Meteorological Monthly(in Chinese),2012,38(2):204-209.
[8]盛杰,毛冬艳,沈新勇,等.我国春季冷锋后的高架雷暴特征分析.气象,2014,40(9):1058-1065.SHENG Jie,MAO Dongyan,SHEN Xinyong.Analysis on characteristics of elevated thunderstorms behind cold fronts in China during spring.Meteorological monthly(in Chinese),2014,40(9):1058-1065.
[9]俞小鼎,姚秀萍,熊廷南,等,2006.多普勒天气雷达原理与业务应用.北京:气象出版社气象,132-134.YU Xiaoding,YAO Xiuping,XIONG Tingnan,et al.The principle and business application of Doppler weather radar.Beijing:China Meteorological Press(in Chinese),2006:132-134.
[10]孙继松,陶祖钰.强对流天气分析与预报中的若干基本问题.气象,2012,38(2):164-173.SUN Jisong,TAO Zuyu.Some essensial issues conneted with severe convective weather analysis and forecast.Meteorological monthly(in Chinese),2012,38(2):164-173,1058-1065.
[11]俞小鼎.强对流天气的多普勒天气雷达探测和预警.气象科技进展,2011,1(3):31-41.YU Xiaoding.Detection and warnings of severe convection with Doppler weather radar.Advances in Meteorological Science and Technology(in Chinese),2011,1(3):31-41.
[12]胡鹏,蔡哲,张永靖,等.一次伴有雷暴的暴雪天气成因机理分析.气象科学,2015,35(2):210-215.HU P eng,CAI Zhe,ZHANG Yongjing,et al.Cause analysis on a snowstorm accompanied with thunderstorm.Journal of the Meteorological Sciences(in Chinese),2015,35(2):210-215.