Abstract: In the eastern part of northwest,north China and northeast China,there is a trend of drought,and the trend of drought is the most significant in north China and the eastern part of northwest China.Especially,the drought in north China may remain a long time.Therefore,the study on severe drought events and their recurrence periods is of great importance.Using the Standardized Precipitation Evapotranspiration Index (SPEI-1） from the 126 stations in north and northeast China from 1901 to 2015 ［the data from November to February (Winter in northern China) was removed］,the study area was divided into 5 climatic zones based on the cluster analysis:The northcentral of northeastern China (I),the southern part of northeast China (II),the southern part of north China (III),the northern part of north China (IV),and the western part of north China (V). The identification criteria of regional severe drought events were defined based on the identification of the strong drought events of a single station using run theory.The applicability of the method was verified by comparing it with the actual drought events and the distribution characteristics and evolution law of the strong drought events in different regions were analyzed.Based on the Copula function with the best fitting goodness,the western part of north China (V) was taken as an example to analyze the recurrence law of the strong drought events and the distribution characteristics of drought duration and drought severity under the same recurrence interval conditions.The results show as follows: (1) The identification criteria of regional strong drought events demonstrated good applicability to the strong drought events in NC and the identified major drought events outside the Drought Disaster Dataset enriched the drought disaster database to some extent. (2) In the 1920s,1940s and 1960s,strong drought events tended to increase,and the number of droughts was increased significantly in the 21st century.The northern part of north China and the southern part of northeast China suffered from more droughts,but the northern part of north China (IV) had the strongest drought and was prone to have prolonged drought events. (3) The general strong drought event in western part of north China (V) has a recurrence period of about 5 years to 6 years.In 1929,1941 and 1965,respectively,a particularly serious drought occurred with a recurrence interval being about 94 years to 102 years,93 years to 101 years and 35 years to 41 years respectively.The Yearly Charts of Dryness/Wetness in China for the Last 500year Period shows that serious drought did occur in these three years,this further proved the reliability of the identification criteria. (4) For the strong drought events with a recurrence period of 2 years,5 years,10 years,20 years,50 years and 100 years respectively,all the strong drought events were most serious in the northern part of north China (IV),followed by those in the western part of north China (V).This paper can provide theoretical basis and reference for further understanding of major drought events in northern China.

Key words: regional strong drought events, north China and northeast China, SPEI index, return period