Spatial-temporal Variation of Extreme Precipitation Events in Northwest China During 1961 -2010

摘要

Using the daily precipitation data of 118 meteorological stations in Northwest China from January 1,1961 to December 31,2010,we analyzed extreme precipitation events from prime precipitation data by applying R-language Climate Index( RClimDex).The spatial-temporal change characteristics in the past 50 years have been examined using the method of trend analysis,Mann-Kendall and the spatial analysis module of Arcgis9.2.The results show that the spatial distribution of the indices for extreme precipitation in Northwest China is greatly influenced by geographic location,atmospheric circulation and topography,and the spatial difference of extreme precipitation events is very evident,while the indices reduce from the southeast to the northwest except Consecutive Dry Days( CDD).In Xinjiang region,high values appear in Tianshan Mountains and decrease towards the south and north respectively.In the past 50 years,the temporal variation tendency of the indices for extreme precipitation in Northwest China has a great spatial distinction.It shows that the variation tendency is opposite between the east( decrease) and the west( increase),and CDD has a decreasing tendency while other indices increase.For each region,it is found that the indices for extreme precipitation in Xinjiang and Qinghai Province shows an increasing trend,and it is remarkable in Tianshan Mountains,the north of Xinjiang and the northeast of Qinghai Province.The temporal variation tendency of the indices for extreme precipitation in Ningxia,Shaanxi and Gansu has a large spatial distinction.The stations which have an increasing tend are mainly found in the north of Ningxia,south of Shaanxi and Hexi Corridor of Gansu.However,the south of Ningxia,north of Shaanxi and Longnan of Gansu Province mainly present a decreasing trend.The temporal variation tendency of the indices for extreme precipitation in Inner Mongolia is not obvious.Overall,the east part of Northwest China has a dry tendency,while the west part has an opposite trend.