中国江南地区降水异常的年际变化与北极海冰密集度异常的相关分析及其机理研究

本文选取最近二十年(1998—2017年)中国江南地区降水和北极海冰为研究对象,分析了年际时间尺度上中国江南地区降水异常与北极海冰异常的关系,并进一步通过研究关键区附近罗斯贝长波(Rossby长波)的波射线路径和中国中纬度地区波作用通量的传播异常,揭示了北极海冰通过Rossby波大气桥的调制作用影响江南地区降水的可能机制。结果表明:夏、秋季东西伯利亚海与巴芬湾的海冰密集度异常与次年中国江南地区降水异常存在显著的正相关关系。其影响机制是:关键海区海冰异常和北极放大能够激发Rossby波列型遥相关从北极关键区向中国中纬度地区传播,而关键区附近的Rossby波扰动能量在夏、秋季比冬、春季更容易传播至中国中纬度地区,并最终通过上下游遥相关效应引发中纬度副热带西风急流异常和急流入口区右侧江南地区的环流和降水异常,当海冰偏多时西风急流加强,江南地区对流不稳定发展,降水偏多。

The Relationship of China Rainfall in the Southern Yangtze River Valley and Arctic Sea Ice Concentration Anomalies on the Interannual Variability

Based on the precipitation products from TRMM(Tropical Rainfall Measuring Mission),sea ice concentration(SIC)data from the Hadley Centre and the NCEP/NCAR(National Centers for Environmental Prediction/National Center for Atmospheric Research)reanalysis data from 1998 to 2017,the relationship between the interannual rainfall anomalies in the southern Yangtze River valley and the Arctic sea ice anomalies was studied and the possible dynamical process of the summer—autumn SIC anomalies in key areas affecting the rainfall in the southern Yangtze River valley were further discussed.The results indicated that the Arctic SIC anomalies were significant positive correlated with the rainfall anomalies of next year.The key marine areas with the strongest correlation were the East Siberian Sea and the Baffin Bay.Their seasonal correlation analysis revealed that the summer—autumn SIC anomalies had the strongest correlation with annual rainfall of next year.In addition,the Rossby wave ray path and anomalous propagation of wave activity flux indicated that the disturbance energy near the key areas were more likely to spread to mid-latitude of China in summer—autumn than winter—spring,which resulting in the circulation anomaly in the southern Yangtze River valley through the upstream and downstream effects.When the SIC were abnormal more,the Rossby wave activity from key areas could spread to mid-latitude in China and enhance the upper level subtropical westerly jet directly,then promote the development of vertical movement and water vapor transport in the southern Yangtze River valley,finally led to abnormal more rainfall.