袁媛,高辉,李维京,柳艳菊,陈丽娟,周兵,丁一汇. 2017. 2016年和1998年汛期降水特征及物理机制对比分析[J]. 气象学报, 75(1):19-38, doi:10.11676/qxxb2017.019
2016年和1998年汛期降水特征及物理机制对比分析
Analysis and comparison of summer precipitation features and physical mechanisms between 2016 and 1998
投稿时间:2016-10-21  最后修改时间:2016-12-08
DOI:10.11676/qxxb2017.019
中文关键词:  汛期降水  长江流域洪涝  超强厄尔尼诺  印度洋暖海温  高原积雪  MJO
英文关键词:Summer precipitation  Flood in YRV  Super El Niño  Warm SSTA in the tropical Indian Ocean  Snow cover in Qinghai-Tibet Plateau  MJO
基金项目:国家重点基础研究发展计划973项目(2013CB430203);公益性行业(气象)科研专项(GYHY201306033、GYHY201406001);国家自然科学基金重点项目(41130960)。
作者单位E-mail
袁媛 国家气候中心中国气象局气候研究开放实验室, 北京, 100081  
高辉 国家气候中心中国气象局气候研究开放实验室, 北京, 100081  
李维京 国家气候中心中国气象局气候研究开放实验室, 北京, 100081;南京信息工程大学气象灾害预报预警与评估协同创新中心, 南京, 210044 liwj@cma.gov.cn 
柳艳菊 国家气候中心中国气象局气候研究开放实验室, 北京, 100081  
陈丽娟 国家气候中心中国气象局气候研究开放实验室, 北京, 100081;南京信息工程大学气象灾害预报预警与评估协同创新中心, 南京, 210044  
周兵 国家气候中心中国气象局气候研究开放实验室, 北京, 100081  
丁一汇 国家气候中心中国气象局气候研究开放实验室, 北京, 100081  
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中文摘要:
      利用多种大气环流、海表温度、积雪面积等数据,并利用个例对比分析和统计方法,研究了2016年汛期(5-8月)中国旱、涝特征及与1998年的异同点,并对比分析了这两年导致降水异常的大气环流和外强迫因子。结果表明:(1)2016年汛期中国降水总体偏多,长江中下游和华北各有一支多雨带。与1998年相比,这两年南方多雨带均位于长江流域,梅雨雨量均较常年偏多1倍以上,但梅雨季节进程有显著差异,1998年发生典型的“二度梅”,而2016年梅雨结束后长江流域降水显著偏少,主要降水区移至北方。(2)2016年5-7月乌拉尔山高压脊明显偏弱,而1998年欧亚中高纬度呈“两脊一槽”型,这与北大西洋海温距平在这两年前冬至春季几乎完全相反的分布型密切相关。(3)这两年5-7月热带和副热带地区环流较为相似,副热带高压偏强、偏西,东亚夏季风偏弱,来自西北太平洋的水汽输送通量均在长江中下游形成异常辐合区,这主要是受到了前期相似的热带海温异常的影响,均为超强厄尔尼诺事件和热带印度洋全区一致偏暖模态。(4)这两年8月环流形势有显著差异,2016年8月副热带高压断裂,西段与大陆高压结合持续控制中国东部上空,夏季风迅速转强,长江流域高温少雨。而1998年8月夏季风进一步减弱,长江流域发生“二度梅”。2016年8月MJO异常活跃并长时间维持在西太平洋地区,激发频繁的热带气旋活动,对副热带地区大气环流的转折有重要作用。而1998年8月MJO主要活跃在印度洋地区,使得副高持续前期偏强的特征。除海洋和上述环流差异外,2016年前冬至春季青藏高原积雪的冷源热力效应远不及1998年强,这可能是导致2016年夏季风偏弱的程度不及1998年,而2016年汛期华北降水较1998年偏多的原因之一。
英文摘要:
      Characteristics of droughts and floods in China during the summer (May-August) of 2016 and 1998 were compared in great detail. The associated atmospheric circulation and external-forcing factors were also investigated and compared for these two years. (1) The precipitation was mostly above normal in China in the summer of 2016, with two main rainfall belts located in the Yangtze River valley (YRV) and North China. Compared with the summer of 1998, a similar rainfall belt occurred in the YRV with the precipitation over 100% above normal. However, the seasonal processes of Meiyu were different. The typical "second Meiyu" occurred in 1998, whereas dry condition dominated the YRV after the end of Meiyu in 2016. (2) During May-July 2016, the Ural high was weaker than normal, but it was stronger than normal in 1998. This difference was resulted from the totally different distribution of sea surface temperature anomaly (SSTA) over the North Atlantic Ocean during the preceding winter and spring of the two years. (3) However, the tropical and subtropical circulations were much similar in May-July of 2016 and 1998. Circulations in both years were characterized by stronger than normal and more westward-extending west Pacific subtropical high (WPSH), weaker than normal East Asian summer monsoon (EASM), and anomalous convergence of moisture flux in the middle and lower reaches of the YRV. These similar circulation anomalies were attributed to the similar tropical SSTA pattern in the preceding seasons, i.e. the super El Niño and strong warming in the tropical Indian Ocean. (4) Significant differences in the circulation pattern were observed in August between the two years. The WPSH broke in August 2016, with the western part combining with the continental high and persistently dominating eastern China. The EASM suddenly became stronger, and dry condition prevailed in the YRV. On the contrary, the EASM became weaker in August 1998 and the "second Meiyu" took place in the YRV. The Madden-Julian Oscillation (MJO) activity became extremely active in August 2016 and stayed in the western Pacific for 25 days. It triggered frequent tropical cyclone activities and further influenced the significant turning of the tropical and subtropical circulation in August 2016. However, MJO was active in the tropical Indian Ocean in August 1998, which was favorable for the maintenance of a strong WPSH. Except for the above ocean factors and atmospheric circulation anomalies, the thermal effect of the snow cover over Qinghai-Tibet Plateau from the preceding winter to spring in 2016 was much weaker than that in 1998. This may explain the relatively stronger EASM and more precipitation in North China in 2016 than in 1998.
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