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北京地区4月份一次罕见暴雪的形成机制分析
杜佳1, 杨成芳2, 戴翼1, 邢楠1, 于波1
(1.北京市气象台;2.山东省气象台)
Formation Mechanism of an Infrequent Blizzard in Beijing in April
Du Jia1, Yang Chengfang2, Dai Yi1, Xing Nan1, Yu Bo1
(1.Beijing Meteorological Service;2.Shandong Meteorological Service)
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投稿时间:2019-03-21    修订日期:2019-08-09
中文摘要: 2018年4月4—5日,北京地区出现了罕见暴雪过程。本文利用雨滴谱仪、多普勒天气雷达、微波辐射计、地面加密自动站、EC再分析资料及气候整编资料等多源观测资料,分析了此次暴雪过程的极端性及形成机制。结果表明:(1)此次过程是北京地区4月份首次出现纯雪日,降雪量和积雪深度均突破历史同期记录,850hPa-1000hPa温度标准化异常SD值均小于-3,日降雪量排在整个冷季的前5%,是一次极端天气过程。(2)低层强冷空气入侵形成冷垫,700hPa强西南低空急流输送充沛水汽,使北京地区上空600hPa到700hPa产生条件性对称不稳定,暖空气在锋区以上的强上升运动触发不稳定能量,产生高架对流,局地雷达回波具有夏季对流单体的倾斜结构特征,有利于暴雪增幅。(3)降雪过程先后受到两次冷空气叠加影响,前期强冷空气持续剧烈降温导致低层温度偏低,使得温度达到降雪阈值,是此次极端降雪过程产生的主要原因。(4)微波辐射计监测显示,降雪的起止时间与逆温具有良好的对应关系,降水相态主要取决于1km以下的温度变化。
Abstract:On April 4-5th, 2018, an infrequent snowstorm stuck the Beijing area. This paper analyzes the extremes and formation mechanism of the blizzard process by using multi-source observation data such as raindrop spectrometer, Doppler weather radar, microwave radiometer, ground encryption automatic station, EC reanalysis data and climate reorganization data. (1) April 5th was the first pure snow day in Beijing in April. The snowfall and snow depth both exceeded the historical record and the 850hPa-1000hPa temperature normalized SD value was less than -3, as a consequence it was an extreme weather process. (2) The invasion of low-level cold air forced the warm and humid air climb along the cold pad. Conditional symmetric instability from 600hPa to 800hPa in Beijing area was caused by strongly warming and humidification from 700 hPa strong southwest low-level jet and triggered by the strong rising motion of warm air above the front, resulting in elevated convection and radar echo like thunderstorm cells in Summer, which enhanced the snowfall. (3) The snowfall process was affected by two cold air superimposition successively. That the continuous violent cooling induced by a strong cold air before the snowfall caused the low level temperature to be extremely low and reach the temperature threshold of snow in Beijing, was the decisive factor for the extreme snowfall. (4) Microwave radiometer monitoring showed that the duration of snowfall had a good correspondence with the inversion temperature, and the precipitation phase mainly depends on the temperature change below 1km.
文章编号:201903210118     中图分类号:    文献标志码:
基金项目:国家重点基础研究发展计划(973计划)
引用文本:
杜佳,杨成芳,戴翼,邢楠,于波,0.[en_title][J].Meteor Mon,():-.
Du Jia,Yang Chengfang,Dai Yi,Xing Nan,Yu Bo,0.Formation Mechanism of an Infrequent Blizzard in Beijing in April[J].Meteor Mon,():-.