欧亚中高纬春季地表感热异常与长江中下游夏季降水的可能联系

利用国家气候中心提供的中国区域753站降水观测资料、ECMWF逐月地表感热通量再分析资料和NECP/NCAR再分析资料,讨论了欧亚大陆中高纬春季地表感热异常与长江中下游夏季降水之间的联系及其相关的物理机制。分析发现欧亚大陆中高纬春季地表感热异常与长江中下游地区夏季降水存在显著的正相关:感热偏强期,长江中下游夏季降水偏多;感热偏弱期,长江中下游夏季降水偏少。春季感热异常偏强时,夏季东亚副热带西风急流主体位置偏东、强度偏强、范围偏大,长江中下游地区主要受辐合上升气流控制,水汽输送条件好,降水异常偏多。而春季感热偏弱时,情况大致相反,则夏季降水异常偏少。研究表明欧亚大陆中高纬春季地表感热通量异常变化对我国长江中下游夏季降水预测具有一定的指示意义。

Possible Linkage between Spring Surface Sensible Heat Flux Anomalies over the Mid-High Latitudes of the Eurasian Continent and Summer Precipitation in the Middle-Lower Reaches of the Yangtze River

On the basis of daily precipitation observations at 743 stations in China and monthly surface sensible heat flux data from the European Centre for Medium-Range Weather Forecasts reanalysis data (ERA40 and ERA-interim) as well as that of NCEP/NCAR reanalysis data, the physical mechanism and possible linkage between spring surface sensible heat flux anomalies in the mid-high latitudes of the Eurasian Continent and summer precipitation over the middle-lower reaches of the Yangtze River is analyzed in this study. The results show a significant positive correlation between them. Further analysis indicates that strong spring surface sensible heating in the mid-high latitudes of the Eurasian Continent always exists concurrently with the eastward shifted and strengthened East Asia subtropical westerly jet. In such a situation, evidently anomalous ascension and divergence of the water vapor transport result in increased summer precipitation over the middle-lower reaches of the Yangtze River. On the contrary, weak surface sensible heating tends to cause less precipitation in this area. Therefore, the spring surface sensible heat flux anomalies over the Eurasian Continent in the mid-high latitudes can be a potential predictor for the summer precipitation prediction in the middle-lower reaches of the Yangtze River.