近159 年东亚夏季风年代际变化与中国东部旱涝分布

利用1850-2008 年我国东部地区90 个测站的旱涝等级和北半球夏季海平面气压格点等资料，使用BP 典型相关等方法，分析了近159 年旱涝等级与东亚夏季海平面气压的耦合相关关系。利用关键区域的海平面气压资料，定义出与我国东部旱涝分布有密切联系的东亚夏季风指数，在此基础上分析了东亚夏季风年代际变化对我国东部旱涝分布的影响。结果表明：(1) 近159 年中国东部旱涝具有4 种典型空间分布型，即华南与中国东部其他地区旱涝趋势相反型、黄淮地区与长江流域及其以南旱涝趋势相反型、江淮流域与中国东部其他地区旱涝趋势相反型和中国东部与西部旱涝趋势相反型。近159 年东亚夏季海平面气压场主要呈现亚洲大陆与西太平洋海平面气压强弱相反的分布特征；(2) 本文定义的夏季风指数的年代际变化与我国东部旱涝典型分布型的年代际变化有密切关系，但两者的相关关系并不是稳定不变的，存在显著的年代际位相差异，即20 世纪20 年代之前，当东亚夏季风偏强(弱) 时，长江流域以北容易偏旱(偏涝)，长江流域及其以南容易偏涝(偏旱)，20 世纪20 年代以后，当东亚夏季风偏强(弱) 时，长江流域以北容易偏涝(偏旱)，长江流域及其以南容易偏旱(偏涝)。可见，使用较长年代资料进行考察，研究结论丰富了大多数使用近50-60 年资料的研究结果。东亚夏季风与我国东部旱涝分布之间关系的年代际位相差异，可能与东亚夏季风对太阳活动等外强迫的非线性反馈相联系

Interdecadal Variations of East-Asian Summer Monsoon and Drought/Flood Distribution over Eastern China in Last 159 Years

Based on the drought/flood grads of 90 meteorological stations over eastern China and summer average sea-level pressure (SLP) during 1850-2008, this paper analyzed the coupling relationship between the drought/flood grads and the East-Asian summer SLP using BPCCA statistical methods. The East-Asian summer monsoon index which is closely related with interdecadal variation of drought/flood distribution over eastern China was defined by using the key areas of SLP. Then, we studied the impact of the interdecadal variation of East-Asian summer monsoon on the drought/flood distribution over eastern China in the last 159 years. The results showed that there were four typical drought and flood spatial patterns in eastern China: the drought/flood distribution in South China was contrary to that of the other areas; the drought/flood distribution along the Huanghe-Huaihe river valleys was contrary to that of the Yangtze River valley and the areas south of it; the drought/flood distribution along the Huaihe River valley was contrary to that of the other areas; and the drought/flood distribution in the eastern areas was contrary to the western areas. The main distribution pattern of the SLP in summer was that the strength of SLP in Asian continent was opposite to that in Western Pacific. The interdecadal variation of drought/flood distribution patterns over eastern China had a close relationship with that of the East-Asian summer monsoon defined in this study, although their correlation was not stable and had a significant difference in interdecadal phase change. When the East-Asian summer monsoon was stronger (weaker), the northern regions of the Yangtze River valley were more susceptible to drought (flood), but the Yangtze River valley and its southern regions were more susceptible to flood (drought) before the 1920s; when the East-Asian summer monsoon was stronger (weaker), the northern regions of the Yangtze River valley were more prone to flood (drought), but the Yangtze River and its southern regions were prone to drought (flood) after the 1920s. It is indicated that by using the data of the longer period more results could be obtained than by using the data of the last 50-60 years. The interdecadal phase differences between the East-Asian summer monsoon and the drought/flood distribution in eastern China may relate to the nonlinear feedback of the East-Asian summer monsoon to the extrinsic forcing (e.g. solar activity).