Wavelet Analysis of Precipitation and Its Distribution in the Piedmont Region of Taihang Mountains—A Case Study at Luancheng Station

A 40-year time series of annual precipitation and its distribution during the growth period of winter wheat at Luancheng Station, Agro-ecosystem Experimental Station of Chinese Ecological Research Network, CAS, located in typical region of Piedmont region of Taihang Mountains, is analyzed by statistic and Mexican Hat Function wavelet analysis. The result shows that the period in different intervals is not stable, but variable. The annual precipitation variation can be divided into two periods, more than mean precipitation before 1980 and less than mean later, on the 40 years scale. On 10 to 30 years scale, it is richer before 1960s and less after 1997, and more or less between them. Furthermore, periodic variation of 5—7 years is found in shorter time scale. In a whole, from now to 2010, annual precipitation will have still a decreasing tendency, but is will be more than that of mean during the coming five years, possibly. Four times of alternate variation, more than mean precipitation before 1967, less from 1967 to 1983, richer from 1984 to 1994 and less after 1995, are found in the whole growing season of winter wheat.