doi:  10.3878/j.issn.1006-9895.1909.18190
1996年冬季一次南方低温事件的低频特征分析及诊断

The analysis of low-frequency characteristics and thermodynamic diagnosis in a Southern low-temperature event in 1996 winter
摘要点击 53  全文点击 12  投稿时间:2018-07-07  修订日期:2019-02-18
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基金:  国家重点研发计划项目,国家自然科学基金项目
中文关键词:  低温事件  准双周振荡  带通滤波  热力学诊断
英文关键词:  Low-temperature events, quasi-biweekly oscillation, band-pass filter, thermodynamic diagnosis
     
作者中文名作者英文名单位
余汶樯Yu Wen-qiang特变电工新疆新能源股份有限公司 风电工程事业部
高庆九Gao Qing-jiu南京信息工程大学大气科学学院 气候动力学研究中心;南京信息工程大学气象灾害教育部重点实验室/气候与环境变化国际合作联合实验室/气象灾害预报预警与评估协同创新中心
引用:余汶樯,高庆九.2020.1996年冬季一次南方低温事件的低频特征分析及诊断[J].大气科学
Citation:Yu Wen-qiang,Gao Qing-jiu.2020.The analysis of low-frequency characteristics and thermodynamic diagnosis in a Southern low-temperature event in 1996 winter[J].Chinese Journal of Atmospheric Sciences (in Chinese)
中文摘要:
      加强大气季节内振荡研究是发展延伸期预报能力的关键之一。研究表明低温形成与冬季风和冷空气的季节内振荡有密切联系。因此,本文利用192站日最低温度观测资料和ERA-Interim再分析环流资料,讨论了偏东路径南下冷空气造成的南方低温事件中准双周振荡特征及低频环流特征,并进行热力学诊断,希望提高对中高纬度地区持续性低温事件中低频信号的认识。结果显示:我国南方地区最低温度存在显著的10-20d振荡周期,低温事件伴随低频振荡的加强而发生。1996年2月17-24日低温过程前后的低频环流场分析表明,西伯利亚及东亚上空的异常高/低压是影响我国大部分地区冬季温度的关键区,系统沿西北东南向低频波列向下游移动,东移特征在中纬度带最明显,异常偏北风引导高纬冷空气向南推进是低温事件爆发的根本原因。垂直结构上,内陆以正压性为主,东亚沿岸表现出斜压性。热力学诊断发现温度局地变化主要受平流项和非绝热项作用,冷平流是维持低温过程的关键。
Abstract:
      Extreme low-temperature events have attracted wide attention due to their persistence and disastrous nature. Many scholars have analyzed the past few decades'' low-temperature events in China from the perspective of interannual and interdecadal variations. Intraseasonal oscillation has been regarded as one of the basic characteristics of atmospheric activity. Strengthening the study of intraseasonal oscillation is one of the keys to the development of extended-range forecasting ability. The study shows that the formation of low temperature is closely related to the intraseasonal Oscillation of winter monsoon and cold air. Therefore, we want to explore the characteristics of quasi-biweekly oscillation in low temperature events to improve the understanding of the low frequency signals of the persistent extreme low temperature events in the middle and high latitudes. Based on in-situ observed daily minimum temperature from 192 stations in China and ERA-Interim reanalysis data, the characteristics of intraseasonal oscillation and low frequency circulation of the southern low temperature events caused by the southward cold air along the eastern path are discussed with band-pass filtering and SVD decomposition and other methods, the thermodynamic diagnosis is carried out as well. Results show that there is a significant 10-20d oscillation period at the minimum temperature in Southern China and 22 sustained low-temperature events in 34 winters during 1979-2013, which occurred with the enhancement of low frequency oscillation are listed. The analysis of the low frequency circulation pattern during the low-temperature event in February 1996 show that the system over Europe is moving downstream along the low-frequency wave train, the eastward shift is most obvious in middle latitude zone, and the abnormal high/low pressure over Siberia and East Asia is the key area which is closely related to winter temperature in most parts of China. The anomalous northerly wind guides the cold air from high latitude to the south is the fundamental cause of the southern low-temperature cold event. On the vertical structure, systems in the troposphere in East Asian coast shows the baroclinicity while the interior are mainly barotropic. Thermodynamic diagnosis shows the local temperature variation is mainly affected by advection term and diabatic heating term because the effect of adiabatic term is too small to be ignored, and cold advection is the key to maintain a low-temperature process. Therefore, the 10-20 day low frequency oscillation activity has an important contribution to the low-temperature event.
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