The copula function-based probability characteristics analysis on seasonal drought and flood combination events on the north China plain

Abstract

Drought and flood events, especially the drought and flood combination events(DFCEs) on the North China Plain (NCP), known as an important grain production region inChina, constitute a serious threat to China's food security. Studies on DFCEs in this regionare of great significance for the rational allocation of water resources and the formulation ofintegrated response strategy for droughts and floods. In this study, L-moments theory andbivariate copula method were used to evaluate the probability characteristics of seasonalDFCEs (continuous drought, continuous flood, and alternation between drought and flood)on the NCP, based on the daily precipitation data (1960-2012) at 19 meteorological stations. Results indicate the following: (1) On the NCP, the precipitation in summer accounts for56.45%-72.02% of mean annual precipitation, and the precipitation in autumn and springcome second. The winter precipitation is the smallest (less than 4%); (2) The best-fit distribution for precipitation anomaly percentages in spring, summer and autumn areGeneralized Normal (GNO), Generalized Logistic (GLO) and Pearson III (P-III) insub-region I, respectively. While in sub-region II, they are respectively the P-III, P-III andGeneralized Extreme-Value (GEV); (3) Compared with the Gumbel copula and Claytoncopula, Frank copula is more suitable for spring-summer and summer-autumn precipitationanomaly percentage sequences on the NCP; (4) On the time scale, continuous droughtrespectively dominate in spring-summer DFCEs and in summer-autumn DFCEs on theNCP. Summer-autumn DFCEs prevail in sub-region I with the average probability value0.34, while spring-summer DFCEs dominate in sub-region II, of which average probabilityvalue is 0.42; (5) On the spatial scale, most areas where the probability of continuousdrought in spring-summer and spring drought & summer flood is relatively high are locatedin the northwest, northeast, and coastal parts of sub-region II; all the events with highprobability of continuous drought in summer-autumn and summer flood & autumn droughtoccurred at the central part in the northwest of sub-region II.