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气象:2016,42(3):280-293
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梅雨期龙卷环境条件与典型龙卷对流风暴结构特征分析
(1.江苏省气象科学研究所,南京 210008;2.江苏省气象台,南京 210008;3.上海台风研究所,上海 200030)
Analysis on Environmental Conditions and Structural Features of Typical Convective Tornado Storm in Meiyu Period
(1.Jiangsu Institute of Meteorological Sciences, Nanjing 210008;2.Jiangsu Meteorological Observatory, Nanjing 210008;3.Shanghai Typhoon Institute, CMA, Shanghai 200030)
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投稿时间:2014-10-26    修订日期:2015-08-25
中文摘要: 利用逐日4次1°×1° FNL/NCEP分析资料及多普勒天气雷达、地面自动气象站等观测资料,在对近十年江苏梅雨期龙卷天气的环境特征进行合成分析并提炼对流参数特征值后,着重对2013 年7 月7日发生在安徽天长至江苏高邮一带导致龙卷的对流风暴的形成和结构特征演变进行了分析。结果表明:江淮梅雨期间,地面中尺度气旋的右侧附近(100 km)、对流层低层中尺度低涡右下方约200~300 km处和低空急流左后侧之间区域是龙卷易发区;梅雨期大气环流背景为龙卷的发生提供了对流层低层充沛的水汽和有利的不稳定层结与动力条件,低层气旋性涡度在龙卷发生前强烈发展,边界层内强的垂直风切变促进了龙卷风暴内气旋性涡度的迅速增强,而对流层低层辐合的增强将有利于初始对流的触发;但梅雨期龙卷对对流不稳定能量蓄积条件要求低于冰雹和雷暴大风;龙卷对流参数特征值及其与气候平均值的差异性为龙卷天气的短期预报提供了参考依据。引发2013年7月7日龙卷的对流风暴起源于地面辐合线附近,地面辐合及中尺度锋区的增强有利于对流风暴的快速发展,此次系列龙卷是由一个生命史较长的超级单体风暴产生,该对流风暴具有典型超级单体的回波特征,风暴内的中气旋维持2 h之久,中气旋相关参数的演变对龙卷的临近预警有较高的参考价值,当中气旋底高较低且中气旋切变值明显增强时,发生龙卷天气的可能性较大。
Abstract:By reanalysis data (1°×1°) 4 times a day from FNL/NCEP, Doppler radar, and automatic weather station (AWS), this paper analyzed the formation and structure characteristics of the convective storms which resulted in tornadoes from Anhui Tianchang to Jiangsu Gaoyou on 7 July 2013 after analyzing on environmental characteristics and feature extraction of convective parameters of tornadoes in Jiangsu Province in recent ten years’ Meiyu period. The results show that during the Meiyu period in Yangtze Huaihe Region, tornadoes are prone to occur in the right side of mesoscale cyclone (100 km), the lower right side of mesoscale vortex (200-300 km) and the left rear of low level jet stream. General circulation in the Meiyu period provides plentiful moisture, favorable unstable stratification and dynamic conditions for tornadoes. The low level cyclonic vorticity develops strongly before tornado. Vertical wind shear in boundary layer promotes cyclonic vorticity in tornado storm to strengthen rapidly, and enhancement of convergence in low troposphere is conducive to initialization of convection. As for tornadoes in Meiyu period, the demand to convective energy accumulation is lower than hails and thunderstorm gales. Bias between convective parameters feature value and climatic average value provides references for short range forecast of tornado. The tornado convective storm that triggered the tornado on 7 July 2013 initialized near surface convergence line. The strength of surface convergence and mesoscale frontal zone contributed to the development of convective storm. The series of tornadoes were produced by a long life super cell storm which had echo characteristics of typical super cell. The mesocyclone inside the storm maintained two hours. Generally, the evolution of the mesocyclone parameters has great reference value to tornado warning, which shows that when the bottom height is low and shear values are significantly enhanced in the mesocyclone, tornadoes are more likely to occur.
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基金项目:公益性行业(气象)科研专项(GYHY201006003和GYHY201206004)、江苏省自然科学基金(BK20131459)、江苏省科技支撑计划(BE2013730和BE2015731)、国家科技支撑计划(2011BAK21B04)和江苏省气象局科研基金(KZ201502)共同资助
引用文本:
曾明剑,吴海英,王晓峰,蒋义芳,2016.梅雨期龙卷环境条件与典型龙卷对流风暴结构特征分析[J].气象,42(3):280-293.
ZENG Mingjian,WU Haiying,WANG Xiaofeng,JIANG Yifang,2016.Analysis on Environmental Conditions and Structural Features of Typical Convective Tornado Storm in Meiyu Period[J].Meteor Mon,42(3):280-293.