Study On Return Period Of Strong Drought Events In Northern China

This paper uses 126 meteorological stations in North China and Northeast China(110-140 ° E,34.5-55 ° N,referred to as North of China),and the monthly scale standardized evapotranspiration index(SPEI-1)from 1901 to 2015 to remove the previous year from November to the next.After the data of February(the northern winter),the results of rotational empirical orthogonal function decomposition(REOF)was used to divide the study area into five climate zones: the north of Northeast(I),the middle of the Northeast(II),the south of Northeast(III),the north of North China(IV)and the south of North China(V),using the run-length theory to identify the single-site strong drought event,and give the identification criteria for regional severe drought events,and Compared with the actual drought events in China's drought disaster dataset,the applicability of the objective identification method of strong drought events was tested.The interdecadal distribution characteristics and evolution law of the severe drought events in northern China were revealed.Based on the optimal Copula function,the strong drought in northern China was analyzed.The recurrence characteristics of events in different regions,and the distribution characteristics of drought duration and drought intensity under the same return period;finally,the main impact of the occurrence of strong drought events Sound factor.The following main conclusions are drawn:(1)Rotating empirical orthogonal function decomposition(REOF)partition results are shown: based on the monthly scale SPEI index,northern China can be divided into five climate zones on the interannual scale,on the interdecadal scale,Northern China can be divided into three districts.(2)The identification criteria of regional severe drought events have good applicability to the severe drought events in northern China.The maximum drought intensity and drought duration are in the 1920 s and 1960 s,and the frequency of drought is significant in the 21 st century.increase.(3)The drought in North China is more serious than that in Northeast China.Strong drought events occur frequently,droughts last a long time,and drought intensity is strong,especially in the 1960 s and 21 st century.The strong drought in the north of North China is the most serious,and it is more prone to drought.(4)Most of the severe drought events in northern China have a quasi-5a cycle.The recurrence period of particularly severe severe drought events is mainly 20 a,30a,40 a,50a and 100 a,which are very different.The drought in 1901,1920,1925,1935,1941,1965 and 1986 was re-emerged in 1929,1932,1944,1957(1947),1997 and1986.In the case of a given univariate return period,the drought in north of North China is the most serious,followed by the south of North China.(5)The strong drought in northern China is mainly due to the continuous transformation of the La Ni?a in the early winter to the El Ni?o phase in the autumn,the common influence of the sensible heat anomalies in the middle and high latitudes of Europe and Asia and its atmospheric teleconnection.