干旱区地理2017，Vol.40Issue(2)：248-256,9.
1470-1912年西北东部地区极端干旱事件的原及分形特征研究
Recovery of extreme drought events and their fractal characteristics in the eastern Northwest China from 1470 to 1912
摘要
Abstract
Northwest China has the lowest quantity of precipitation in the same latitude of the Northern Hemisphere and its main climatic disaster is drought.By using rich literature historical records in China to rebuild the chronology of extreme drought events and increase research on the evolution law of the drought not only can provide historical similarity of extreme climatic events that may occur in the future,but also has the important significance and value for preventing disasters and reducing damages.Because of the complexity of extreme drought,the simple linear theory and research methods can't meet the research of the complex system of natural disasters.In this paper,we used fractal theory to reproduce the original research object and research the self-similarity of extreme drought system.Studying the similarity of whole and partial,and finding the new order between macro and micro,between entirety and parts,can deepen our understanding of the characteristics of extreme drought and provide a new method to analyze the reasons of extreme drought events.Through collecting historical data about drought disasters from 1470 to 1912 in the eastern northwest China and the drought intensity,duration and range,we defined heavy drought events,built the factor model of extreme drought,reconstructed the extreme events of eastern northwest China for 443 years.Furthermore,by using scale transformation method,this paper calculated the time fractal dimension of different kinds of extreme,droughts from 1470 to 1912 in the eastern northwest China,and mined the time series fractal dimension characteristics of extreme drought events and the relationship between fractal dimensions and distribution structure by using the least squares method,which is of great significance for overall understanding the regularity of occurrences of extreme drought events in northwest China and its occurrence and countermeasures.The results show:(1) There were 22 extreme drought events from 1470 to 1912,among which extreme drought of type Ⅰ has the largest times,type Ⅱ is second and type Ⅲ is the least.(2) The temporal fractal dimension of the drought disasters of the whole series reduces with the increasing of extreme drought intensity,shows inverse correlation with extremely drought period.Different types of extreme drought events have their own recapitulation law in time domains:the lighter the drought degree is,the wider the scale-free area is;the higher the fractal dimension is,the more obvious the short period is.Extreme drought disasters have different levels and they have their respective time recapitulation law:the lower the level is,the shorter the time recapitulation law will be.(3) In the entire period,the dynamic of different levels of the extreme drought disasters present that the overall extreme drought,type Ⅰ and type Ⅲ underwent a series of evolution that occurred from disordered to ordered,and then gradually to non-equilibrium conditions from disordered to ordered;while the early type Ⅱ distributed more orderly and then went into the state of disordered,finally its fractal dimension decreased and its extreme drought events became more concentrated.关键词
西北东部地区/极端干旱事件/分形维数Key words
eastern northwest China/extreme drought events/fractal dimension分类
天文与地球科学引用本文复制引用
毕硕本,蒋婷婷,钱育君,瞿颖..1470-1912年西北东部地区极端干旱事件的原及分形特征研究[J].干旱区地理,2017,40(2):248-256,9.基金项目
国家自然科学基金项目“中国明清时期气候灾害时空演变特征挖掘研究”(编号:41271410) （编号:41271410）
