Periodic Variation of Sunshine Duration from 1953 to 2014 in Lishui
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Abstract:
Based on the monthly sunshine dataset from the Lishui observation station from 1953 to 2014, the trend analysis method is used to analyze the interannual, decadal and seasonal trends of sunshine duration, and then the Morlet wavelet transform and MTM (MultiTaper Method) are applied to study the periodic characteristics of sunshine duration, and the significant periodic signals are reconstructed by MTM, to further study the lesssignificant periods on different time scales with the oscillation time of evolution. The results show that sunshine duration exhibits very significant decline trend in Lishui, with a rate of 3.5 percent per 10 years. The maximum sunshine duration is in summer, followed by that in autumn. The Morlet wavelet and MTM analysis results show that quasi12year cycle is the most significant in the whole time domain, with regular alternating positive and negative oscillations and the maximum spectral density; in addition, the cycles of 6 years and 2 to 4 years cycle are also apparent. The MTM reconstruction analysis indicates that the amplitudes of quasi12year periodic signals vary with time, and there are three distinct and slowly varying envelopes.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.