Abstract: North China Plain,located in the mainland monsoon circulation of Eastern Asian,severely and repeatedly suffers from drought hazards. As the ratio of potential-evapotranspiration and precipitation,aridity index is an important index to characterize the meteorological factors and water-heat balance condition. Based on meteorological data of 59 stations in North China Plain during 1960-2014,tendency of aridity index was analyzed. The temporal characteristics showed that annual mean aridity index at North China Plain basically unchanged. And within the year,aridity index in winter was the highest,followed by spring,autumn,and summer. The spatial characteristics show that the aridity indexes in many parts of Henan Province were descending,while most areas in North China Plain beyond Henan Province were ascending. Ordinary Kriging interpolation method was used because its precision was the highest compared with IDW and Spline when it came to interpolate the spatial distribution of aridity index. Interpolation results indicate that annual mean aridity index of North China Plain from 1960 to 2014 was 0.97-3.50,gradually reducing from west to east,from north to south,from northwest to southeast. Meanwhile,this paper also discussed the characteristics of aridity index periodicity and mutation using the Morlet wavelet function and the Mann-Kendall abrupt test. There existed periodicity in aridity index and the main period was about 15a,and based on this main period,we predicts that 2015-2016 and 2024-2031 or so will be a wet climate period,accordingly 2016-2024 will be a drought climate period. There was no evident abrupt change in the study period at North China Plain. During 1960-2014,potential evapotranspiration, precipitation,wind speed,sunshine hours,moisture and vapor pressure all significantly decreased,while temperature significantly increased. Finally,principal component analysis and multiple linear regression were used to analyze the meteorological factors contribution to aridity index. Results show that the first principle component was moisture factor, the second were sunshine duration and wind speed,and the third were air hot and cold status. Meanwhile,the moisture factor had the greatest effect on aridity,and showed a negative effect,followed by sunshine duration and wind speed factors which showed positive effects;the air hot and cold status was a minimal factor for a positive role. This paper revealed the relationship between aridity index and various meteorological factors,analyzed periodicity of aridity index and predicted its change in the future years. This work plays a significant role in strengthening regional drought study and improving the capability of combating the climate change.

Key words: North China Plain, aridity index, Morlet wavelet function, Mann-Kendall abrupt test, principal component analysis