Analysis on Inner-annual Inhomogeneity Characteristic of Extreme Precipitation Events over Northwest China

Based on the daily precipitation datasets from 1960 to 2004 recorded at the 112 stations in the five provinces of northwest China,the extreme precipitation threshold of different stations were defined by centesimal value method,the inner-annual inhomogeneity characteristics of extreme precipitation events were analyzed by introducing the new parameters that reflect the temporal distribution of extreme precipitation events:concentration degree(ECD) and concentration period(ECP).The result showed that the average and anomalous spatial distributions of ECD and ECP all existed obvious spatial difference in northwest China,and their anomalous spatial distribution all can be divided into six key areas,namely the north Xinjiang area,the loess plateau and Ningxia plain area,the Qaidam Basin and Hexi Corridor area,the south Xinjiang area,the south Qinghai plateau area,and the Qinba mountainous area.As for temporal distribution of extreme precipitation events,the ECD and ECP all existed remarkable inter-decadal vibration in these six key areas,but their distribution characteristic was inconsistent.Besides,the change tendency was inversed between in the east and in the west of the northwest China.