The annual precipitation series from 1952~2003 in Yan an was analyzed through multi-time-scale by using Morlet wavelet.The results showed that the changes of 3~6 and 25~32 years scale were stronger,and there were nearly 22 and 3 years period with 22-year periodic changes most strongly.According to precipitation cycle,the Yan an annual precipitation in the next 5~8 years will be relatively high,to reach the maximum in 2007~2009,and then to begin to reduce. The precipitation from 2013 will enter a stage of dr...
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