The Temporal-spatial Characteristics Of Drought/Flood Disasters In The Middle And Lower Reaches Of The Yellow River From 1470 To 1911

With the exception of global climate change,historical climate has become one of the important contents of Past Global Changes(PAGES)and Climate Variability and Predictability(CLIVER).This paper collectes and classified the records of the drought and flood in the middle and lower reaches of the Yellow River region from 1470 to 1911,vectorized the history map of the study area,established historical spatio-temporal database about records of drought and flood,and then reconstructed the sequence of drought/flood grade year by year,site by site.Uses a variety of spatio-temporal statistical methods to analaze the evolution of drought/flood disasters in the middle and lower reaches of the Yellow River region,such as Ensemble Empirical Mode Decomposition(EEMD),Empirical Orthogonal Function(EOF)and Rotated Empirical Orthogonal Function(REOF).By dividing the sensitive climatic zoning to discuss the response of the drought/flood occurred to the East Asian summer monsoon and the change of the solar activity at different time scales.In order to investigate the law of spatio-temporal and its possible cause of drought/flood evolution in the middle and lower reaches of the Yellow River region.The result shows:(1)Reconstruction the sequence of drought and flood in the middle and lower reaches of the Yellow River from 1470 to 1911,the overall drought occurred slightly more than the flood and drought disasters averageintensity greater than floods.(2)During the 442 years,there are 7 obvious mutation in 50a scale,mainly experienced 3 stages:drought/flood grade moves around the axle of long-time average annual value five times from 1470 to 1595,at the same time,the drought period slightly more than flood.lt was same fluctuations ups and downs from 1596 to 1765,but the flood time bucket logger than drought.Overall performance for the prtial drought at the beginning,then turned to partial waterlogging,drought/flood grade was below years of average from1766 to 1911.There are six periods of 3a,5a 7a 16a,25a and 87a of the drought/flood,among them 3a,5a,16a and 87a belongs to the whole performance of the main change cycle,and the 7a,25a cycle in individual time performance is weaker.(3)According to the spatial distribution of disaster frequency,the drought disaster is mainly concentrated in the northern part of the region of Shanxi,Northern Shaanxi and the northwest of Shandong peninsula;The flood disaster mainly concentrated in the eastern region,eastern district is more than the west,South more the North..EOF decomposition results show that,change of drought and waterlogging mainly exist four distinct spatial distribution pattern,namely "the same anomaly in whole area","opposite anomalies in the West and East,"opposite anomalies in theSouthwest to Northeast",and "+,-,+"type of distribution from West to East.In addition to this,drought/flood change existing five sensitive areas in the middle and lower reaches of the Yellow River area according to the REOF analyses,respectively in South and Central region,the western region,East,Southwest,North.(4)During the 442 yaers,there are variation periods of quasi 3a and quasi 5a and quasi 16a,quasi 25a of the East Asian summer monsoon,89aperiod of quasi century scale change,and the period of the century scale change of 147a.The change cycle of drought/flood in the lower reaches of 3a,5A,quasi periodic variation of quasi 16a and quasi 25 A is consistent with the Yellow River.(5)East Asian summer monsoon and solar activity affects obviously the force change of drought/flood but has a large difference between in different regions.When the years East Asian summer monsoon is strong(weak),along with the solar activity strong(weak),is conducive to the regional drought(flood)hazards in the NO.1 to 4 climate sensitive partition areas(Central-Southern area,the western area,the eastern area,the Southwest area).In contrast is the N0.5(North area),when the years the East Asian summer monsoon is strong(weak),along with solar activity is weak(strong),is conducive to the regional flood(drought)hanppens.