510年来中国东中部地区气候干湿变化研究

Study on Dry and Wet Climatic Changes of Eastern and Mid-China Region in Recent 510 Years

选择上海、武汉、天津和西安为典型区,以1470—1979年逐年干湿等级序列为基本数据源,应用墨西哥帽小波变换方法,对中国东中部地区近510a来不同时间尺度下的气候干湿变化与气候突变特征进行分析,并探讨气候干湿变化的动因。结果显示:19世纪以前气候干湿变化表现出较明显的东西差异;小冰期事件、18世纪气候温和期等非局地性事件在较大区域都有反应,但各地的具体响应程度、方式和时间均有差异;在20世纪气候变暖的大背景下,各地气候均向偏干旱方向演变。百年以上尺度气候干湿变化的原因主要是太阳辐射及其引起的大气环流变化,百年以下尺度的变化则与季风系统短尺度波动、区内各个大气环流系统的相互作用、局地下垫面差异和人类活动等复杂因素的影响有关。

Historic records are considered as important data sources in climatic change study.To reveal evolution rules and trends of dry and wet climate in Eastern and Mid-China area,four places (Shanghai,Wuhan,Tianjin and Xi'an) are selected,all of which locate in the East-Asia monsoon controlling scope.The data of drought and waterlogging grades,from 1470 to 1979 in four places,are used to establish dry/wet series,which are calculated using method of Mexican Hat wavelet transformation.Then multi-time scale wavelet transformation graphs and abrupt change points of dry-wet climate of each place in the recent 510 years are obtained.The analyzing results show that the dry and wet phases in 270 a and 135 a time scale are similar between Shanghai and Tianjin(in East China) or Xi'an and Wuhan(in Mid-China).For 70 a and 30 a time scale,there are more frequent fluctuations of dry and wet climate in Xi'an than in other regions.Dry and wet climatic changes respond obviously to the Little Ice age of the 17^(th) century and comparatively stable age of the 18^(th) century in East China,but tardily or unsteadily in Mid-China.However,climate of each region is changing to dry after the 20^(th)century,which relates with possibly the warming occurrence in the early part of the 20^(th) century.As a whole,dry and wet climate changes in Eastern and Mid-China area display some East-west differences before 18^(th)century,and are trending towards coherence. Effect elements of dry and wet climate changes are discussed too.Transformation of atmosphere circulation systems due to non-local climatic changes and relative sea-land position control the dry-wet changes in long time scale.The differences of physical local environment and human activity are the effect elements to climate change in short time scale,and are only some interferential element to climatic evolution trends.