Temporal And Spatial Distribution Characteristics And Cause Analysis Of Drought And Flood Disasters In Central China In Qing Dynasty

In recent years,With the increasing global climate change,the drought and flood disasters events of our country intensified.In this paper,the historical data of drought and flood disaster in 1644-1991 in Central China were collected,the database of historical drought and flood disaster data was established and the drought and flood disaster grade series was reconstructed.We use modern climate statistical method,such as the heuristic segmentation algorithm(BG segmentation),complementary ensemble empirical mode function(CEEMD),empirical orthogonal function(EOF),cross-wavelet power spectrum and cross-wavelet coherence spectrum and so on,to analyze the spatial-temporal evolution of flood and drought disaster in Central China in Qing Dynasty,and to explore its mechanism.The results show:(1)Collecting and compiling the data of drought and flood disaster in Central China from 1644 to 1911,and establishing the historical drought and flood disaster grade of each state and the whole region.From the whole time series,The drought and flood disaster grade series in Central China showed a slight increase,followed by a slight decline,and then a rising trend.The flood disaster of each grade is more than that of drought disaster.(2)Using the trend fitting method,moving average method,accumulative anomaly method,BG segmentation,CEEMD and significance test method,this paper analyzed the century distribution characteristics,phased distribution characteristics,mutation characteristics and periodic characteristics of the drought and flood disaster grade series of Central China from 1644 to 1911.?The flood disaster in addition to 1644-1699 years,the rest of the time are higher than the drought disaster,and the frequency of the grade of floods are higher than drought disasters.?There were obvious phased changes in the drought and flood disaster grade series in central China in Qing Dynasty.It has five drought and six waterlogging period.?The mutation of the drought and flood disaster grade series occurred in 1702,after the mutation,the drought to flood.?There are significant cycles of 2.8a,6.9a,10.6a,21.1a,55.6a and 100.9a in the drought and flood disaster grade series.(3)From the spatial distribution of view,drought disaster of Central China from 1644 to 1911 in Changsha,Lizhou,Wuchang and Huangzhou state is more serious.Flood disaster in Changsha,Hanyang,Anlu,jizhou state is more frequent.Drought and flood disaster average annual disaster distribution map,it has similar spatial distribution characteristics with the flood and drought disasters,and also some differences.(4)The results of EOF decomposition show that the cumulative variance contribution rate of the first 11 spatial modes of the drought and flood disaster grade in the central China was 85.51%.The first mode for the consistency of drought and flood disasters as the main feature,as the drought and flood disasters were more than(less),At the same time,other typical fields mainly show the regional differences in the whole region,such as the spatial characteristics of the southern and northern,central and the surrounding.(5)The results of cross-wavelet coherence,wavelet phase-spectrum and correlation coefficient method analysis show that there are different degrees of correlation between sunspot numbers and drought and flood disasters in Central China in different periods.The cross wavelet power spectrum shows that there is a close relationship between 3 and 14 years and different degrees of influence in different time periods,while the wavelet coherence spectrum shows that there is a strong resonance period of from 4 to 30 years.There is a significant correlation between the flood and drought disaster in Central China and the East Asian summer monsoon in interdecadal change.The correlation coefficient between them shows negative in North in spatial distribution.Its zero line is located on the coast of the Yellow River.(6)Central China from 1784 to 1786 extreme drought events,resulting in most areas of a scene of utter desolation.Grain total crop failure.River,lake,wells and springs continuous dry.The price of rice is expensive.People flee.Sell children.People starved to death are everywhere.people as food.