罗然1, 郑永光1,2, 陈敏3
Mechanism of a Rare Nocturnal Sudden Intense Warming Event in Beijing and Surrounding Area
luo ran1, ZHENG Yongguang1,2, CHEN Min3
(1.Chinese Academy of Meteorological Sciences;2.National Meteorological Centre;3.Institute of Urban Meteorology,China Meteorological Administration)
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投稿时间:2019-08-08    修订日期:2020-03-02
中文摘要: 夜间降温是正常的地表气温日变化,但统计表明北京及周边地区冬半年时常出现入夜后气温不降反升的现象,甚至出现了小时升温超过10℃的剧烈增温事件。这种增温具有明显的突发性,且很快转为降温,常对业务预报造成困扰。2010年11月26日夜间冷锋过境该区域造成了最强达12 ℃/h的夜间急剧增温事件,同气候统计结果相比,该次增温幅度和影响区域范围非常罕见极端。本文对其进行了详细诊断分析,使用的资料包括自动气象站、常规地面和探空、铁塔、卫星、风廓线雷达等观测资料和美国环境预报中心(NCEP)最终分析资料。分析结果表明,该次过程对流层低层有非常显著的冷平流;垂直速度诊断、卫星和风廓线雷达观测都表明,对流层中低层都存在显著的强下沉运动;铁塔观测和北京探空观测演变都表明增温过程中近地面大气有显著的湍流运动。总结该次罕见过程的机理包括3个方面:高原地区地面位温显著高于平原地区(二者最大可差10 K)是该次罕见增温事件形成的首要条件,而强下沉运动使得低密度高位温空气强迫下沉到边界层是增温必要条件,而强湍流混合作用则是地面空气增温的必要机制。估算结果表明,边界层急流伴随的强湍流混合可引起约8℃的罕见地面空气增温。最后,给出了该次事件的机理概念模型。
Abstract:Surface temperature normally decreases after sunset, but a great many nocturnal sudden intense warming events are observed in winter in Beijing and surrounding area, and the most intensity of temperature rise could be greater than 10℃/h. These sudden warming events are followed rapidly by temperature dropping, which have been causing great difficulty in forecasting. This paper has detailedly analyzed a rare intense nocturnal warming event with the most intense rise of 12 ℃/h, with a cold front passing through Beijing and surrounding area at the night of November 26th, 2010, whose intensities of temperature rise and affected area are rare and extreme compared with the statistical climatological results. This analysis is based on the data of automatic weather stations, conventional surface stations and rawinsonde, meteorological observation tower, stationary meteorological satellite, and wind profiler, and the reanalysis data of NCEP. The results show that, during the event, there was significant cold advection in the lower troposphere, and significantly strong downward motion in the middle and lower troposphere presented by diagnosed vertical velocity and the data from the satellite and the wind profiler. The temporal evolution of both the meteorological tower observations and soundings of Beijing indicates that the boundary layer had strong turbulence. Therefore, this rare warming event was caused by significant surface potential temperature differences between the plateau and the plain, strong downward adiabatic warming and intense turbulent mixing with strong boundary layer jet. The estimate shows that the turbulent mechanical mixing associated with the low-level jet caused about 8℃ temperature increase. Finally, the conceptual model of this event is presented.
文章编号:201908080303     中图分类号:    文献标志码:
罗然,郑永光,陈敏,0.[en_title][J].Meteor Mon,():-.
luo ran,ZHENG Yongguang,CHEN Min,0.Mechanism of a Rare Nocturnal Sudden Intense Warming Event in Beijing and Surrounding Area[J].Meteor Mon,():-.