2018年春末南方极端持续高温及MJO影响
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国家科技支撑计划资助项目(2015BAC03B04);国家重点研发计划资助项目(2017YFC1502103)


Persistent extreme high temperature event in southern China in late spring of 2018 and the effect of Madden-Julian Oscillation
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    摘要:

    本文分析了2018年春末我国南方地区持续性极端高温过程及其影响系统。本次事件自5月15日首先在江淮等地迅速发展,17日之后扩展至华南并在该地区维持至6月初。江南南部和华南东部等地高温日数比常年同期偏多6~10 d,累计近两千站次出现了35℃以上的高温天气,约是之前最多年(1991年)的2.6倍。研究区域内有超过三分之一的测站高温日数突破5月历史极值。统计分析结果显示,春末南方高温日数与该地区上空位势高度、其西侧经向风及其上空对流活动均有显著关系,但对流的影响更为超前,约在一周左右。除和华南地区对流呈显著正相关外,春末南方高温还和热带印度洋OLR(Outgoing Longwave Radiation)呈显著的负相关,这种相关模态和MJO(Madden-Julian Oscillation)的第一、二位相对应的对流异常分布一致。对2018年的个例分析支持这一统计结果。2018年5月,MJO有20 d持续位于这两个位相,且振幅均超过1,是有MJO监测以来5月这两个位相最多的一年。因此,无论是统计分析还是个例都表明MJO对本次春末南方高温有重要影响。

    Abstract:

    A persistent extreme high temperature(HT) event occurred in southern China in late spring of 2018.It began on May 15 and developed rapidly in the Jianghuai region,then spread southward to southern China beginning May 17,and remained in the region until early June.The HT days in the southern reaches of the Yangtze River and east part of southern China are approximately 6-10 days greater than the climatology.The accumulated HT frequencies with maximal air temperatures over 35℃ reach nearly 2 000,which is 2.6 times greater than the second largest value in the research period.In May 2018,more than 1/3 of the stations in southern China broke the historical records of HT days of May.The statistical analyses show that the HT days in southern China in late spring (May 16-31) are significantly related to the 500 hPa geopotential heights and convection over the area,as well as the 850 hPa meridional wind speed over its west side.However,the effect of the convection is more advanced,with a leading influence of about one week.Aside from the local circulations,the convection over the tropical Indian Ocean has a significant negative correlation with the HT frequency.A case study of circulations in 2018 also supported this statistical result.The spatial differences of convection may be linked to the activities of MJO.In May 2018,MJO remained in phases 1 and 2 for 20 days with amplitudes exceeding 1.The days in these two phases are the largest in May since 1981.Both the statistical analysis and case study indicate that MJO has an important impact on the HT events in southern China in late spring of 2018.

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  • 收稿日期:2018-09-28
  • 最后修改日期:2018-12-05
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  • 在线发布日期: 2019-02-14

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