阿留申低压次季节尺度异常对北太平洋冬季降水的影响分析

利用1979—2018年的冬季逐日气象数据,研究了北太平洋地区冬季（12月至次年2月）阿留申低压次季节尺度变化特征,分析了次季节尺度阿留申低压异常与降水和极端降水异常之间的联系。选择1979—2018年共40个阿留申低压次季节尺度从异常增强到减弱的完整事件,记录下每个位相具体日期运用于合成分析。通过合成分析的结果可知：次季节尺度阿留申低压异常增强（减弱）时,北太平洋海盆区的降水呈现出明显的东多（少）西少（多）,同时副热带西太平洋略偏多（少）的分布型。次季节尺度蒸发异常和整层水汽输送散度异常能够解释以上降水异常的空间分布。在阿留申低压异常偏强时,自北太平洋中部向东北延伸至北美沿岸区域内大气河发生频率增加,使得海盆中部向东和东北汇聚更多的水汽,北美西海岸地区更易发生极端降水事件。

Impact of intraseasonal oscilation of Aleutian Low on winter precipitation over North Pacific Ocean

Based on the meteorological daily data from 1979 to 2018, the intraseasonal oscillation of the Aleutian Low (AL) and its connection with normal and extreme precipitation in winter (December to February of the following year) over North Pacific Ocean were investigated. This study selects 40 complete AL intraseasonal oscillation events from 1979 to 2018 with anomalous strengthening and then weakening evolution. Exact date of each phase is recorded to conduct composite analysis. Results shows that the distribution of precipitation anomalies presents a "east positive-west negative" (east negative-west positive) pattern over the North Pacific with the abnormal strengthening (weakening) of AL,meanwhile, positive (negative) anomaly is observed over the subtropical western Pacific. The intraseasonal anomalies of evaporation and divergent of integrated water vapor transport can account for the spatial distribution of precipitation anomalies over the North Pacific. The frequency of Atmospheric Rivers increases from the central North Pacific to the North American coastal area when the AL is abnormally strong. As a result, more moisture converges over the eastern and northeastern North Pacific from the center basin,and more extreme precipitation tends to occur over the west coast of North America.