| Wavelet analysis of precipitation variation and trend in nearly 50 years in Yan’an |
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| DOI：10.7606/j.issn.1000-7601.2008.04.43 |
| Key Words: wavelet analysis nearest neighbor bootstrapping regressive model Yan’an |
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| Abstract: |
| The annual precipitation series from 1952～2003 in Yan’an was analyzed through mult-i timescale by using Morlet wavelet．The results showed that the changes of 3～6 and 25～32years scale were stronger and there were nearly22and3years period with22-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 drier period for about10years．The annual precipitation predicted model was established on the basis of wavelet and nearest neighbor bootstrapping regressive method by the annual precipitation data from1952 to1990 then the model was used to predict 13-year annual precipitation changes from 1991 to 2003．There was11years prediction results with relative error less than 30％ this showed that the comprehension wavelet analysis and nearest neighbor bootstrapping regressive method can be used to predict the precipitation changes． |