2016年初冬陕西一次高架雷暴天气过程分析
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摘要
利用常规地面高空观测资料、西安和安康多普勒天气雷达观测资料、欧洲中心细网格模式预报等资料对2016年11月22日发生在陕西地区的一次雷暴过程进行诊断分析,结果表明:陕西中南部雷暴区位于地面冷锋后350～500 km的区域内,雷暴区3 km以下是深厚的冷垫,同时中低层存在明显的逆温层,低层是绝对稳定的大气层结,这说明此次雷暴天气为高架雷暴。通过诊断饱和假相当位温、假相当位温、湿位涡和绝对涡度表明不同地区不稳定机制是不同的。西安地区不稳定机制为条件性对称不稳定,安康地区不稳定机制为条件性不稳定。在条件性对称不稳定区域,降雪回波呈现出数个平行带状回波,与0～6 km风切变矢量(西西南风)平行;在条件性不稳定区域,降水回波为小尺度的块状回波。强垂直风切变表明大气斜压性强,中高层暖湿气流增强了大气的湿斜压性,从而使中高层形成条件性对称不稳定,产生倾斜对流;中低层偏南气流输送暖平流和水汽,使得大气较为暖湿,中高层温度平流较弱,大气较干,形成位势不稳定,锋面抬升中低层暖湿大气使其饱和,位势不稳定转化为条件性不稳定,产生垂直对流。不稳定与上升运动及回波高度有着较好的对应关系。
Based on conventional observation data, Xi an and Ankang Doppler weather radar observation data and ECMWF numerical model data(0. 25°×0. 25°), an elevated thunderstorm process in Shaanxi in early winter of 2016 is analyzed. The results show that the thunderstorm area in the center and south of Shaanxi Province was located in the area of 350-500 km after surface cold front. Deep cold air cushion existed under 3 km in thunderstorm area. At the same time, there was temperature inversion in middle-low level and absolute stability of atmospheric stratification in low level. All these make clear that the thunderstorm was an elevated one. Through analyzing moist potential vorticity, saturated pseudo-equivalent potential temperature, pseudo-equivalent potential temperature and absolute vorticity, we found that the unstable mechanism is different in different regions. Unstable mechanism for Xi'an Region is conditional symmetric instability while unstable mechanism for Ankang Region is conditional instability. In conditional symmetric instability area there are a number of parallel snowfall echoes, parallel with vertical wind shear vector from 0 to 6 km. In conditional instability area there are small scale echoes. The strong vertical wind shear indicates that the atmospheric baroclinic is strong. Warm moist air flows between middle-high layers enhance atmospheric baroclinicity,thus producing conditional symmetric instability which results in slantwise updraft. Southerly airflow in the low-middle level convey warm advections and water vapor which makes the atmosphere moister and warmer, making the atmosphere moister and warmer, but highlevel temperature advection is weak and the atmosphere is relativerly dry. So potential instability is formed. When the front surface uplift warm moist air makes it saturated, potential instability changes into conditional instability, resulting in vertical convection. Thus, there is a good correspondence between the instability and the ascending motion and the echo height.
Based on conventional observation data, Xi an and Ankang Doppler weather radar observation data and ECMWF numerical model data(0. 25°×0. 25°), an elevated thunderstorm process in Shaanxi in early winter of 2016 is analyzed. The results show that the thunderstorm area in the center and south of Shaanxi Province was located in the area of 350-500 km after surface cold front. Deep cold air cushion existed under 3 km in thunderstorm area. At the same time, there was temperature inversion in middle-low level and absolute stability of atmospheric stratification in low level. All these make clear that the thunderstorm was an elevated one. Through analyzing moist potential vorticity, saturated pseudo-equivalent potential temperature, pseudo-equivalent potential temperature and absolute vorticity, we found that the unstable mechanism is different in different regions. Unstable mechanism for Xi'an Region is conditional symmetric instability while unstable mechanism for Ankang Region is conditional instability. In conditional symmetric instability area there are a number of parallel snowfall echoes, parallel with vertical wind shear vector from 0 to 6 km. In conditional instability area there are small scale echoes. The strong vertical wind shear indicates that the atmospheric baroclinic is strong. Warm moist air flows between middle-high layers enhance atmospheric baroclinicity,thus producing conditional symmetric instability which results in slantwise updraft. Southerly airflow in the low-middle level convey warm advections and water vapor which makes the atmosphere moister and warmer, making the atmosphere moister and warmer, but highlevel temperature advection is weak and the atmosphere is relativerly dry. So potential instability is formed. When the front surface uplift warm moist air makes it saturated, potential instability changes into conditional instability, resulting in vertical convection. Thus, there is a good correspondence between the instability and the ascending motion and the echo height.
引文
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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[M].北京:气象出版社:95-96.
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Mesoscale Meteorology in Midlatitudes[M]. Chichester,Wiley-Blackwell:407.
段亚鹏,王东海,刘英,2017.“东方之星”翻沉事件强对流天气分析及数值棋拟[J].应用气象学报,28(6):666-677.
侯淑梅,王秀明,尉英华,等,2018.山东省初秋一次大范围强对流过程落区和抬升触发机制分析[J].气象,44(1):80-92.
黄小刚,费建芳,孙吉明,等,2017. 2013年冬季长江中下游地区一次高架雷暴过程的成因分析[J].气象学报,75(3):429-441.
黄晓龙,高丽,2016. 2014年3. 19台州冰雹过程中尺度分析[J].气象,42(6):696-708.
农孟松,赖珍权,梁俊聪,等,2013. 2012年早春广西高架雷暴冰雹天气过程分析[J].气象,39(7):874-882
沈杭锋,张红蕾,高天赤,等,2016.浙江盛夏一次强对流天气的特征及其成因分析[J].气象,42(9):1105-1113.
盛杰,毛冬艳,沈新勇,等,2014.我国春季冷锋后的高架雷暴特征分析[J].气象,40(9):1058-1065.
寿绍文,2010.位涡理论及其应用[J].气象,36(3):9-18.
寿绍文,励申申,姚秀萍,2003.中尺度气象学[M].北京:气象出版社:153-154.
覃靖,潘海,刘蕾.2017.柳州“4·09”致灾冰雹的超级单体风暴过程分析[J].气象,43(6):745-755.
王秀明,俞小鼎,周小刚,2014,雷暴潜势预报中几个基本问题的讨论[J].气象,40(4):389-399.
吴乃庚,林良勋,冯业荣,等,2013. 2012年初春华南“高架雷暴”天气过程成因分析[J].气象,39(4):410-417.
肖安,许爱华,2018.三小时负变压异常指数及对强对流天气的预报意义[J].气象学报,76(1):78-91.
徐芬,郑媛媛,慕熙昱,等,2016.江苏沿江地区一次强冰雹天气的中尺度特征分析[J].气象,42(5):567-577.
薛谌彬,陈娴,吴俞,等,2017.雷达资料同化在局地强对流预报中的应用[J].大气科学,41(4):673-690.
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[M].北京:气象出版社:95-96.
俞小鼎,周小刚,Lemon L,等,2010.强对流天气临近预报[M].北京:中国气象局培训中心:5-6.
俞小鼎,周小刚,王秀明,2016.中国冷季高架对流个例初步分析[J].气象学报,74(6):902-918.
张一平,俞小鼎,孙景兰,等,2014. 2012年早春河南一次高架雷暴天气成因分析[J].气象,40(1):48-58.
Colman B R, 1990a. Thunderstorms above frontal surfaces in environments without positive CAPE. Part I:a climatology[J]. Mon Wea Rev,118:1103-1121.
Colman B R, 1990b. Thunderstorms above frontal surfaces in environments without positive CAPE. Part II:organization and instability mechanisms[J]. Mon Wea Rev,118:1103-1122.
Grant B N, 1995. Elevated cold-sector severe thunderstorms:a preliminary study[J]. Natl Wea Dig,19(4):25-31.Markowski P, Richardson Y,2010.
Mesoscale Meteorology in Midlatitudes[M]. Chichester,Wiley-Blackwell:407.