30年来中国干旱时空规律演变特征

The evolution characteristics of drought spatio-temporal law in China in the recent 30 years

气候变化背景下,不断摸清我国干旱时空演变规律和新变化,对干旱防灾减灾应对、水资源开发利用和生态环境保护有着十分重要的作用。基于历史逐日气象干旱综合指数(MCI),采用特征指标及统计方法,对30年来全国及十大流域干旱气候特点、年代际及总体变化趋势、极端特征等进行分析,主要结论如下:(1)1991—2020年平均年干旱强度全国有两个高中心,分别位于黄淮、江淮、江汉大部一带,以及华南南部和云南、四川东南部、贵州西部等地;干旱日数多发区与强度高中心基本一致。(2)虽然近3个年代干旱强度总体呈现逐渐减少态势,但干旱极端偏强年份时有发生,干旱强度高中心空间位置及范围存在明显的年代际变化,以20世纪90年代范围最广。(3)空间变化趋势,西南南部、江南南部、华南东部等地干旱呈现增强趋势,而长江以北大部分地区及华南西部则呈减弱趋势,仅部分站点趋势显著;就十大流域而言,北方流域干旱减弱,南方趋强,西南诸河流域趋重明显。(4)云南中东部、广西西北部、贵州西南部、海南等地为最强连续干旱强度和最长连续干旱日数高值中心;北方大部分流域年干旱强度和日数极端最强、最多的年份主要出现在20世纪末和21世纪初,而南方长江、珠江、西南诸河流域则出现在近5年之内。

Under the background of climate change,continuously understanding the evolution characteristics of the spatio-temporal law and the new changes of drought in China plays a very important role in drought prevention and mitigation response,water resources development and utilization,and ecological environmental protection.Based on the historical daily Meteorological Drought Composite Index(MCI)in China,the characteristic indices and statistical methods were used to analyze the climate characteristics,inter decadal change and overall change trends,and extreme feature of drought in China and the ten major river basins in the recent 30 years,and the main conclusions are as follows:①There were two high centers of annual drought intensity averaged from 1991 to 2020,which one is located in Huanghuai,Jianghuai and most Jianghan regions,and the other in south part of South China,Yunnan,southeastern Sichuan,and western Guizhou.The areas with frequent drought days were basically the same as the centers with high intensity.②Although the overall drought intensity has generally shown a gradual decrease in the recent three decades,extreme drought years occur from time to time.There are obvious inter-decadal changes in the spatial location and range of the center of high drought intensity,with the widest range occurring in the 1990s.③Since 1991,annual drought intensity have shown strengthening trend in the south of Southwest China,southern Jiangnan,eastern South China etc.,while weakening trend in most areas of north part to the Yangtze River and western South China.Only the trend of some stations is significant.As far as the ten major river basins are concerned,the drought have weakened in northern and strengthened in southern river basins.The southwest river basin has become significantly heavier.④Central and eastern Yunnan,northwestern Guangxi,southwestern Guizhou,and Hainan are the high centers with the strongest continuous drought intensity and the longest continuous drought days.The years with strongest drought intensity and most drought days in most northern river basins are occurred at the end of the 20th century and the beginning of the 21st century.But in the Yangtze River,Pearl River and Southwest River basins appeared in the recent five years.