The 2016 summer floods in China and associated physical mechanisms: A comparison with 1998
The 2016 summer floods in China and associated physical mechanisms: A comparison with 1998
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DOI：
10.1007/s13351-017-6192-5
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发表时间：
2017-05
影响因子：
3.2
通讯作者：
Yuan Yuan-Yuan;Hui Gao;Weijing Li;Yanju Liu;Lijuan Chen;Bin Zhou;Yihui Ding
中科院分区：
文献类型：
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作者：
Yuan Yuan-Yuan;Hui Gao;Weijing Li;Yanju Liu;Lijuan Chen;Bin Zhou;Yihui Ding
对2016年和1998年夏季（5月至8月）中国干旱和洪水的特征以及相关的大气环流和外强迫因素进行了详细比较。获得以下结果。 （1）2016年夏季，我国降水多为偏多，长江流域和华北地区有两大降雨带。与1998年相比，长江流域出现类似的降雨带，降水量偏多100%以上。但梅雨的季节过程却有所不同。 1998年出现了典型的“二次梅雨”，而2016年长江流域则以干旱为主。（2）2016年5-7月，乌拉尔高压偏弱，但1998年偏强。这种差异是由于前冬、春季北大西洋海温异常分布差异较大所致。 (3) 但2016年5-7月和1998年热带、副热带环流系统较为相似。这两年的环流系统均表现为西太平洋副热带高压(WPSH)偏强且西伸，东亚夏季风(EASM)偏弱，长江中下游水汽通量异常辐合。这些相似的环流异常归因于前几个季节相似的热带海温异常，即超厄尔尼诺现象和热带印度洋的强烈变暖。 (4)8月份环流格局两年间存在显着差异。 2016年8月西太副高压解体，其西部与大陆高压结合，持续主宰中国东部。东亚夏季风突然增强，长江流域普遍干燥。相反，1998年8月东亚夏季风较弱，长江流域发生了“二次梅雨”。 2016年8月，马登-朱利安涛动（MJO）异常活跃，在西太平洋停留了25天。它引发了频繁的热带气旋活动，并进一步影响了2016年8月热带和副热带环流的显着转向。相比之下，1998年8月MJO在热带印度洋上空活跃，有利于维持较强的副高。除上述海洋因素和大气环流异常外，2016年冬至春季青藏高原积雪的热效应远弱于1998年，这可能是2016年东亚夏季风相对较强、华北地区降水较1998年偏强的原因。
The characteristics of droughts and floods in China during the summers (May–August) of 2016 and 1998 were compared in great detail, together with the associated atmospheric circulations and external-forcing factors. Following results are obtained. (1) The precipitation was mostly above normal in China in summer 2016, with two main rainfall belts located in the Yangtze River valley (YRV) and North China. Compared with 1998, a similar rainfall belt was located over the YRV, with precipitation 100% and more above normal. However, the seasonal processes of Meiyu were different. A typical “Secondary Meiyu” occurred in 1998, whereas dry conditions dominated the YRV in 2016. (2) During May–July 2016, the Ural high was weaker than normal, but it was stronger than normal in 1998. This difference resulted from fairly different distributions of sea surface temperature anomalies (SSTAs) over the North Atlantic Ocean during the preceding winter and spring of the two years. (3) Nonetheless, tropical and subtropical circulation systems were much more similar in May–July of 2016 and 1998. The circulation systems in both years were characterized by a stronger than normal and more westward-extending western Pacific subtropical high (WPSH), a weaker than normal East Asian summer monsoon (EASM), and anomalous convergence of moisture flux in the mid 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 up in August 2016, with its western part being combined with the continental high and persistently dominating eastern China. The EASM suddenly became stronger, and dry conditions prevailed in the YRV. On the contrary, the EASM was weaker in August 1998 and the “Secondary Meiyu” took place in the YRV. The Madden–Julian Oscillation (MJO) was extremely active in August 2016 and stayed in western Pacific for 25 days. It triggered frequent tropical cyclone activities and further influenced the significant turning of tropical and subtropical circulations in August 2016. In contrast, the MJO was active over the tropical Indian Ocean in August 1998, conducive to the maintenance of a strong WPSH. Alongside the above oceanic factors and atmospheric circulation anomalies, the thermal effect of snow cover over the Qinghai–Tibetan 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 abundant precipitation in North China in 2016 than those in 1998.