530年来中国东部旱涝分区及北方旱涝演变

The Regional Division of Dryness/Wetness over Eastern China and Variations of Dryness/Wetness in Northern China during the Last 530 Years

使用我国东部地区530年来100个站的旱涝等级序列作REOF分解,根据前7个旋转空间模上高荷载区分布,将中国东部地区分成7个旱涝气候区,即东北区、华北北区、华北南区、西北区、长江中下游地区、华南区及西南区.在分区基础上,着重研究了中国北方季风边缘地带旱涝演变特征.自1470年以来中国北方的旱涝存在明显的阶段性和区域性.16～17世纪上半叶,中国北方干旱频繁,尤其在东北区、华北南区及西北区普遍出现严重干旱.18～19世纪,华北北区干旱发生较多,东北区以涝为主;而华北南区及西北区旱涝交替发生,但变化幅度相对较缓.华北北区及华北南区分别在19世纪末及20世纪初突然从涝相气候跃变为旱相气候,这两地区的干旱持续近百年,是我国北方干旱最严重的地区.五百多年中,东北区、华北北区及西北区极端干旱呈现出相似的变化趋势,具有两头多而中间显著减少的特征;而华北南区一直是极端干旱多发区.中国北方各个旱涝气候区的旱涝具有多时间尺度的年代际振荡特征.4个地区的旱涝变化都存在20～30年时间尺度的周期振荡;除西北区外的三个地区的旱涝变化都存在70～80年时间尺度的周期振荡;东北区及西北区的旱涝变化存在40～50年时间尺度的周期振荡;另外,准10年时间尺度的周期振荡存在于华北北区和南区.

By applying rotated empirical orthogonal function (REOF) analysis on dryness/wetness (DW) series from 1470 to 1999 at 100 selected stations over the eastern part of China, defined by the large contours of the seven REOF modes, 7 dryness/wetness active centers are identified: Northeast China, northern North China, southern North China, Northwest China, the middle and lower Yangtze River valley, South China and Southwest China. The temporal variations of regional dryness/wetness for monsoon boundary zone in northern China are investigated on the basis of the regional division of dryness/wetness. Dryness occurred fairly frequently in Northeast China, southern North China and Northwest China in the 16th century and the first half of the 17th century. In the 18th and 19th centuries, the occurrence of dryness is more frequent in northern North China, but the occurrence of wetness is more frequent in Northeast China, dryness/wetness occurred alternately in southern North China and Northwest China. The changes of dryness/wetness jumped from wetness to dryness in northern North China and southern North China during the late 19th century and the early 20th century respectively. Dryness had kept still in two divisions.The study shows extreme dryness has similar trend, which increased at both ends and less in the middle in Northeast China, northern North China and Northwest China during the last 530 years. But it is a frequently occurring area in southern North China.