2015/2016年海洋和大气环流异常对中国夏季降水的影响

利用1981年1月-2016年8月中国160个气象站降水量资料和NCEP/NCAR资料,对比分析了2015/2016年的主要海洋和大气环流异常及其对夏季降水的影响。结果表明：1）2015和2016年夏季降水异常分布有着明显的差异。2015年夏季降水呈南多北少特点;2016年夏季降水明显增多,尤其是北方地区,且呈现经向型分布。2）热带印度洋-太平洋海温状况监测显示,2015年海温异常表现为El Niño发展年、热带印度洋全区一致模态海温偏暖、印度洋偶极子正位相;2016年海温异常表现为El Niño结束年、热带印度洋全区一致模态海温偏暖、印度洋偶极子负位相。3）2015年,受热带印度洋-太平洋海温异常影响,使得夏季西太平洋副高偏强、偏南,再配合中高纬冷空气活跃,西风急流轴位置偏南,导致我国降水北少南多。4）2016年,受El Niño衰减、印度洋偶极子负位相影响,副高偏北;叠加印度洋海温偏暖的“充电器”效应,副高偏强;同时冷空气偏北偏弱,西风急流轴位置偏北,导致长江中下游及以北区域降水偏多。

Oceanic and Atmospheric Circulation Anomalies in 2015 and 2016 and Their Impacts onSummer Precipitation in China

The differences of oceanic and atmospheric circulation anomalies between 2015 and 2016 are analyzed and their impacts on summer precipitation in China are investigated in this paper by using the monthly precipitation data of 160 stations in China and NCEP/NCAR monthly data. The results show that the distributions of summer precipitation anomalies are obviously different in 2015 and 2016. The summer precipitation anomalies are less over North China, but more over South China in 2015. Compared with 2015, the summer precipitations in 2016 increase obviously, especially in northern China, forming a longitudinal rain belt. The abnormal sea surface temperature (SST) in 2015 is corresponding to the development year of El Niño, warm phase of basin-wide SSTA variation in the tropical Indian Ocean (IOBW) and positive phase of Tropical Indian Ocean Dipole (TIOD), while the SST in 2016 shows the ending year of El Niño, warm phase of IOBW and negative phase of TIOD. In 2015, the western Pacific subtropical high is stronger and more southward than normal under the effect of SST anomalies in the tropical Indian-Pacific Ocean. It combined with active cold airs and southward westerly jet axis and thus resulted in the less precipitation over northern China and more precipitation over southern China. In 2016, El Niño decay and negative TIOD led the subtropical high northward, and the battery charge caused by warm IOBW led subtropical high stronger. The northward and stronger subtropical high met with weak cold air and northward westerly jet axis, which caused more precipitation in the middle and lower reaches of Yangtze River and the region north to it.