长江中下游旱涝的环流型与赤道东太平洋海温遥相关波列特征

CHARACTERISTICS OF TELECONNECTION WAVE TRAIN FOR CIRCULATION PATTERN OF FLOOD/DROUGHT IN THE MIDDLE AND LOWER REACHES OF YANGTZE RIVER AND SEA SURFACE TEMPERATURE OVER EQUATORIAL EASTE PACIFIC

根据长江中下游地区夏季旱涝年前期冬、春季北太平洋海温分布特征进行分析研究 ,提出了影响区域性旱涝的海温“强信号”概念 ;探讨了北半球大气环流结构对赤道东太平洋海温异常响应问题 ,并研究了东太平洋海温与北半球夏、春季高度偏差场季尺度相关偏差场波列结构相关特征。研究结果表明 ,赤道东太平洋海温异常可能通过低纬walker环流引起赤道西太平洋区域性大气异常运动 ,从而产生遥响应环流型 ,形成类似PNA遥相关“大圆波列”。此类遥响应特征在西太平洋区域表现出与副热带高压、西风槽、阻塞高压等相关的系统的准定常经向波列。研究结果还表明此类经向波列结构描述了中高纬地区系统对低纬异常海温遥响应的动力学特征。应用 1997～ 1998年冬季实际海温资料 ,并在赤道中东太平洋地区引入实际海温异常的敏感性试验 ,较成功地模拟了 1998年夏季长江流域洪涝的降水分布特征。文中从统计、动力分析和数值模拟综合分析方法揭示出由前期东太平洋海温异常引起的大气环流变异 ,构成中国长江流域旱涝的物理图像及其动力学模型。

Based on the study of SST characteristics of North Pacific in pre-winter and spring of summer flood/drought in the middle and lower reaches of Yangtze River, the concept of SST 'strong signal' which affects regional flood/drought is put forward. While choosing the SST key areas, the response of the general circulation in Northern Hemisphere to SST anomaly of equatorial Eastern Pacific is discussed further. The correlation between East Pacific SST and the seasonal height difference of North Hemisphere is studied also. It is shown that, the abnormal vertical motion in the equatorial Weste Pacific via Walker circulation may respond to SST anomaly in the equatorial Easte Pacific, and form the PNA-like Great Circle wave train. In addition, the wave train manifests as systems related to subtropical high, westerly trough and blocking high, showing quasi-stationary meridional waves feature. This kind of wave train structure describes the tele-response dynamic features of local flood/drought at mid and high latitudes to abnormal SST at lower latitude. The observational SST anomalies for 1997—1998 winter are introduced into the model CCM3, and the result of the sensitivity experiment describes the summer flooding in 1998 in Yangtze River Valley. The results of statistical and dynamical analyses and numerical simulations show that the preceding SST anomalies may result in the anomalies of general circulation of atmosphere, forming the physical picture and the dynamic model of flood/drought in Yangtze River Valley.