北大西洋-东亚和北亚型遥相关的机制及其对新疆夏季旱涝的影响

北大西洋-东亚和北亚（简称NAENA）型遥相关是夏季欧亚大陆对流层上层经向风异常的第二主导模态，对欧亚大陆多尺度气候变率有显著影响。本文在分析NAENA型维持的动力学机制的基础上，研究了该遥相关型对新疆夏季旱涝异常的影响及其可能机制。大气波列的涡度收支分析表明，气候态的旋转纬向风引起的扰动涡度平流可以被扰动旋转经向风引起的平均涡度平流所补偿。能量转换过程分析表明，该大气波列有效地从平均流中提取有效位能，通过斜压能量转换过程得以维持。大西洋海温异常三极子模态则是NAENA型维持的重要外强迫因子。回归分析表明NAENA型遥相关能通过促进南疆夏季降水，显著影响新疆的旱涝异常。NAENA型位于中亚的气旋性低压一方面增强了南疆地区的垂直上升运动，同时气旋性环流将更多的水汽输送到该地区，有利于水汽在对流层中低层的异常辐合，进而对南疆的降水有促进作用。

Mechanisms underlying the North Atlantic-East and North Asia pattern and its impact of on the summer drought and flood anomalies in Xinjiang, China

The second mode of 200 hPa meridional wind over the Eurasian continent, known as the North Atlantic-East and North Asia (NAENA) pattern, has a significant impact on the multi-scale climatic variability in Eurasia.This paper examined the NAENA pattern''s influence on summer drought and flood anomalies in Xinjiang, China, as well as its possible mechanism, based on an analysis of the NAENA pattern''s maintenance mechanism.The vorticity budget analysis of atmospheric wave train shows that the advection of perturbed vorticity by the climatological rotational zonal wind can be compensated by the advection of mean vorticity caused by the anomalous rotational meridional wind.The energy conversion analysis indicates that the NAENA pattern is maintained mainly through the baroclinic energy conversion from the basic flow with the North Atlantic SST tripolar pattern being the important external driving factor for maintaining the NAENA pattern.Moreover, regression analysis shows that the NAENA pattern can significantly affect drought and flood anomalies in Xinjiang by promoting Southern Xinjiang summer precipitation.When the NAENA pattern is in phase with a cyclone over Central Asia, the vertical ascending motion in Southern Xinjiang tends to be above normal;however, more water vapor is transported into Southern Xinjiang, leading to an anomalous increase in precipitation over Xinjiang.This study is of great significance because it reveals the mechanisms of summer drought and flood in arid areas of northwest China, which is conducive to climate prediction and disaster prevention and mitigation.