Multiscale Variation of Annual Freezing and Thawing Indexes in Shihezi

LUO Na-na;Bake Batur;WU Yan-feng;College of Prataculture and Environmental Sciences,Xinjiang Agricultural University;Northeast Institute of Geography and Agricultural Ecology,Chinese Academy of Sciences;

freezing and thawing index;;ensemble empirical mode decomposition;;temperature;;multiscale variation;;Shihezi;;Xinjiang

Based on the average daily temperature data from 4 meteorological stations in Shihezi during the period of 1961-2013,the variation of annual freezing and thawing indexes was investigated,and the multiscale variation was analyzed using the ensemble empirical mode decomposition. The results showed that the freezing index was in a significant decrease trend with a rate of-3. 84 ℃ ·a-1in recent 53 years,but the thawing index was in a significant increase trend with a rate of 8. 64 ℃ ·a-1. The inter-annual fluctuation of the freezing index was high with an amplitude of 820. 3-1 900. 7 ℃. The fluctuation of annual thawing index was relatively low with a range of3 518. 8-4 577. 9 ℃. There was a significant negative phase between the freezing index and mean air temperature,their inter-annual periods were the same( 3 years),and their decadal periods were similar( about 10 years).However,there was a positive phase between the thawing index and the mean air temperature,and their inter-annual periods were all for 3 years. Accompany with the nonlinear increase trend of temperature,the freezing index was in a nonlinear decrease trend,and the thawing index was in a nonlinear increase trend.