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半干旱区一次罕见“雷打雪”天气形成机制分析
刘晓岳1,2, 于海鹏3, 朱昌权4, 盛夏4, 赵庆云5,6, 马玉霞5, 苟尚6
(1.兰州大学大气科学学院;2.半干旱气候变化教育部重点实验室;3.中国科学院西北生态环境资源研究院寒旱区陆面过程与气候变化重点实验室;4.中国人民解放军93811部队86分队;5.兰州大学大气科学学院,半干旱气候变化教育部重点实验室;6.甘肃省气象局兰州中心气象台)
Mechanism Analysis of a Rare “Thunder Snow” Process in Semi-arid Areas
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投稿时间:2019-08-01    修订日期:2020-10-16
中文摘要: 本文利用气象观测资料、NCEP再分析资料和Himawari-8卫星资料,分析了2017年10月8日~10月9日发生在西北半干旱区一次罕见的雷暴伴雪过程,并对其成因和机制进行了探讨。结果表明:本次冷季罕见的对流天气形成于青藏高原东部,是在槽前地面暖中心的背景下发展的,具有地基雷暴的特征;而出现在兰州的雷暴,距离地面冷锋约150km,有深厚稳定的冷垫,中低层有明显的逆温层,逆温层之上存在条件性不稳定的暖湿空气,具有高架雷暴的结构特征。与东部湿润区高架雷暴不同:本次高架雷暴是青藏高原地区的地基雷暴移动到较低海拔冷垫之上的延续和发展;就结构特征而言:本次过程各特征层次(冷垫、逆温层、水汽辐合等)对应的高度与东部低海拔地区相比明显偏高,但各层次对应的厚度则没有显著差异;就冷垫形成机制而言:西北半干旱区陆气能量交换以感热为主,独特的下垫面在较强冷空气的配合之下,地形复杂的黄土高原地区同样也能形成较为稳定的冷垫层次;从不稳定机制来看:青藏高原地基雷暴和兰州高架雷暴均是由条件性不稳定引发的。青藏高原东部100°E附近“上冷下暖、上干下湿”,在高空急流和500hPa高空槽共同作用下产生上升运动,触发垂直对流;兰州地区中层较强的暖湿平流,不仅向对流层中层提供了充沛的水汽,还加强了逆温层上的条件性不稳定层结;700 hPa切变线辐合作用配合500 hPa高空槽的天气尺度强迫,触发上升运动并释放不稳定能量,为由高原东移至冷垫之上的垂直对流的维持和发展提供了有利的条件。
Abstract:In this paper, the meteorological observation data, NCEP reanalysis data, Himawari-8 satellite data, etc. are used to analyze a rare thunderstorm in the northwest semi-arid region from October 8 to 9, 2017. Its causes and mechanisms were discussed. The results show that the rare thunderstorm process originated from the eastern part of the Qinghai-Tibet Plateau, which was developed in the background of a ground warm center in the in front of the trough, and had the characteristics of surface-based convection. The thunderstorms in Lanzhou, about 150 km away from the ground front, occurred with a deep and stable cold air cushion. There were obvious inversion layers in the middle and lower layer, and warm and humid air with conditional instability above the inversion layer, which has the structural characteristics of elevated thunderstorms. The process is different from the thunderstorm in the eastern humid region in the following aspects. In terms of its development and evolution, this elevated thunderstorm is actually the continuation and development of the surface-based thunderstorm in the Qinghai-Tibet Plateau, which moved to the cold air cushion in lower elevation. In terms of the structural characteristics, the heights corresponding to each feature level (cold air cushion, inversion layer, etc.) in this process were significantly higher than those in the low-altitude areas in the east, but there was no significant difference in the thickness of the corresponding layer. In terms of the formation mechanism of the cold air cushion, the land-atmosphere energy exchange in the semi-arid area of the northwest is dominated by the sensible heat. With the combined effect of the unique underlying surface and strong cold air, the loess plateau with complex topography can also form a relatively stable cold air cushion. From the perspective of instability mechanism, the surfaced-based thunderstorm in east of the Qinghai-Tibet Plateau and the elevated thunderstorm are both caused by conditional instability. The structure of “cold and dry in the upper level, warm and wet in the lower level” was observed in the east of the Qinghai-Tibet Plateau. The updraft was induced under the combined action of high-altitude jet and 500hPa high-altitude trough. In Lanzhou, the strong warm-wet advection in the middle troposphere enhanced the conditional instability above the inversion layer. The convergence effect of 700hPa shear line cooperating with the synoptic-scale forcing of 500hPa trough triggered the ascending motion and released the unstable energy, which provided favorable conditions for the maintenance and development of vertical convection that moved eastward from the plateau to the cold air cushion.
文章编号:201908010300     中图分类号:    文献标志码:
基金项目:国家自然科学基金(41705077)和甘肃省青年科技人才托举工程共同资助
引用文本:
刘晓岳,于海鹏,朱昌权,盛夏,赵庆云,马玉霞,苟尚,.[en_title][J].Meteor Mon,():-.
LIU Xiaoyue,YU Haipeng,ZHU Changquan,Sheng Xia,ZHAO Qingyun,MA Yuxia,Gou Shang,.Mechanism Analysis of a Rare “Thunder Snow” Process in Semi-arid Areas[J].Meteor Mon,():-.