1735—1911年汉江流域季节旱涝等级序列的重建与特征分析

Reconstruction and characteristics analysis of series of seasonal drought/flood grades over Hanjiang River Basin during 1735-1911

基于汉江流域雨雪分寸等史料记录的特点,以发生地区、影响程度和持续时间为衡量标准,提出了利用史料重建汉江流域季节旱涝等级序列的方法,重建了1735—1911汉江流域7府(州)四季的旱涝等级序列,据此分析了各府(州)1735—1911年季节上的旱涝变化特征。结果表明:①汉中府、兴安府、商州和南阳府有更多的春季、夏季、冬季偏旱年,而郧阳府、襄阳府和安陆府有更多的春季、夏季偏涝年和秋季偏旱年;②夏季和秋季旱涝等级的波动明显,而春季和冬季旱涝等级的波动较小;③年代际尺度上来看,汉江流域,1820s—1840s偏涝,1850s、1870s偏旱;④影响较大的季节连旱事件多发生在19世纪,而影响较大的季节连涝事件多发生在夏季和秋季。这一研究,对汉江流域定量化气候研究具有一定的价值,也为汉江流域未来的降水变化研究提供了数据支持。

Variation features for seasonal drought/flood over the Hanjiang River Basin have important climatic meaning because of its special geographical location.The study basin is located in the south-north transitional zone of geography and climate in China,as well as the starting point of the Middle Route of South-to-North Water Transfer Project in operation.In this paper,data sources were historical documents including records from a unique historical archive named Yu-Xue-Fen-Cun and collections from local gazettes and other historical information.A total of 31752 records according to different time resolutions,districts,record classes from 1736 to 1911 were collected from Yu-Xue-Fen-Cun archive with about 179 records yearly,and 2542 records from 1735 to 1911 were collected from other historical documents with about 14 records yearly.Based on the features of historical documents over the Hanjiang River Basin,methods with 3 standards of spatial distributions,severity and duration were put forward as the way for reconstructing seasonal drought/flood grades over the Hanjiang River Basin.And then drought/flood grades for 7 prefectures in the basin in spring,summer,autumn and winter were reconstructed for characteristic analysis in the study area during 1735-1911 AD.The results showed that:1)Compared with other prefectures in the Hanjiang River Basin,there were more drought events in Shaanxi province and Nanyang prefecture in spring,summer and winter,while there were more drought events in autumn and more flood events in spring and summer in Hubei province.2)More obvious fluctuations existed in the drought/flood grades in summer and autumn,while less existed in spring and winter.3)For the whole basin,more flood events occurred during the 1820 s-1840 s,and more drought events happened in the 1850 s and 1870 s.4)More successive drought seasons with greater severity were observed in the study basin in the 19 th century;and most successive flood events with serious severity occurred in summer and autumn.This study has certain value for quantitative climate research in the Hanjiang River Basin,and also can provide data support for future precipitation variation research in the study area.