石河子地区年冻融指数的多尺度变化特征

基于石河子地区各气象站点1961─2013年的逐日平均气温数据,计算年冻融指数,并利用集合经验模态分解(EEMD)分析其多尺度变化特征。结果表明:在过去53 a,石河子地区冻结指数和融化指数的年际变化明显,其中冻结指数总体呈减少趋势,融化指数总体呈增加趋势,气候倾向率分别为-3.84℃·a-1和8.64℃·a-1。在年际变化上,冻结指数年际波动较大,其变幅为820~1 900.7℃;融化指数年际波动较小,变幅为3 518.8~4 577.9℃。在年代尺度上,冻结指数与气温呈明显的负相位,且两者的年际变化周期相同(3 a),年代尺度周期大致相当(10 a左右);融化指数与气温呈明显的正相位,且两者存在年际变化的同周期(3 a)。变化趋势特征表明,伴随着气温的增加,冻结指数呈非线性减少趋势,而融化指数呈非线性增加趋势。

Multiscale Variation of Annual Freezing and Thawing Indexes in Shihezi

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-1 in 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 of 3 518.8-4 577.9 ℃.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.