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文章摘要
引用本文:张剑明,廖玉芳,蒋元华.2017.2015年湖南冬汛成因分析.气象,43(10):1186-1197.
2015年湖南冬汛成因分析
The Causes for the Winter 2015 Flooding in Hunan Province
投稿时间:2016-03-01  最后修改时间:2017-06-29
DOI:10.7519/j.issn.1000-0526.2017.10.003
中文关键词: 冬汛,环流,ENSO,PDO
英文关键词: winter flooding, general circulation, ENSO, PDO (Pacific Decadal Oscillation)
基金项目:湖南省气象局2016年重点科研课题(XQKJ16A004)、中国气象局气候变化专项(CCSF201525)和2015年湖南山洪地质灾害防治气象保障工程项目共同资助
作者单位
张剑明 湖南省气候中心,长沙 410118 
廖玉芳 湖南省气候中心,长沙 410118 
蒋元华 湖南省气候中心,长沙 410118 
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中文摘要:
      本文基于气象观测资料、再分析资料和国家气候中心提供的百项气候系统指数集,利用气候事件机理诊断和气候统计等方法,重点从降水背景、大尺度环流异常及外强迫因子对气候异常影响,分析2015 年湖南罕见冬汛及其成因机制,本文对2015年湖南冬汛及其可能成因进行了分析,结果表明:(1)2015年11月湖南省平均降水量偏多1.6倍,为1961年以来同期第一高位,其中湘东南部分地区降水量超过250 mm,出现气象洪涝。(2)在湖南11月降水处于偏多的年代际背景下,大气环流异常是导致湖南发生冬汛的最直接的原因,2015年11月西太平洋副热带高压偏强、偏西,引导来自印度洋、太平洋地区水汽向东亚地区输送,加上西路冷空气影响导致11月降水异常偏多。(3)在PDO暖位相时发生的El Ni〖AKn~D〗o事件可能是湖南降水异常的重要外强迫条件,赤道中东太平洋和印度洋海表温度异常偏高,导致该区域上空出现强的异常上升运动,而在海洋性大陆区域上空出现了一个异常下沉气流区,这有利于西太平洋副热带高压的加强、西伸,在东亚低纬地区上空出现异常下沉气流区,中纬地区上空出现异常上升气流区,造成该区域强烈的异常辐合,导致该地区持续阴雨天气。
英文摘要:
      The characteristics and its possible mechanisms of winter flooding in Hunan in 2015 were investigated. The results show that: (1) The monthly mean precipitation in Hunan was 1.6 times more than the annual mean, which was recorded as the most for the corresponding period since 1961. Meanwhile, the precipitation amount was more than 250 mm in parts of southeastern Hunan, where flooding occurred. (2) Because the precipitation amount in November was above the normal precipitation, the atmospheric circulation anomaly was the most direct cause for the winter flooding in Hunan. The unusually positive precipitation anomalies in November was produced from the stronger location of Western Pacific Subtropical High (WPSH) and the larger western extension of its ridge, which easily transported water vapor from India and Pacific to East Asia and met the cold air down to southern China. (3) When the Pacific Decadal Oscillation (PDO) was in positive phase, the El Ni〖AKn~D〗o event was important external forcing condition for abnormal precipitation. The sea surface temperature of the central and eastern equatorial Pacific and Indian Ocean were anomalously above average, leading to the enhanced anomalous ascending motion over these oceans, while the anomalous descending motion over the Maritime Continent and its surrounding area occurred. These were favorable for the westward stretch of the WPSH, the anomalous descending motion over the low latitude East Asia, and the anomalous ascending motion over the mid latitude regions. The abnormal Hadley circulation caused strong convergence over the mid latitude, which led to continuous rain weather in these areas.
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