基于SPEI的新疆干旱时空变化特征

SPEI-based Spatiotemporal Variation of Drought in Xinjiang

基于新疆地区54个气象站1963—2012年的逐月气象资料,计算得到近50 a来新疆12个月时间尺度的标准化降雨蒸散指数（SPEI）序列,并利用线性趋势、经验模态分解（EMD）及经验正交函数（EOF）等方法,对新疆近50 a干旱时间和空间变化特征进行了分析。结果表明：新疆地区以1987年为界,由普遍干旱期转型为相对湿润期,但近10 a又出现显著的变干趋势,预示着新疆有可能会重新进入干旱期。新疆干旱变化存在2、6、24 a左右的主要振荡周期以及3～4 a的次振荡周期,其中6 a振荡周期最为突出。EOF展开的第一模态反应的是西风系统控制下,新疆全区干旱变化的平均状态。EOF展开的第二模态则反映出由于天山山脉阻隔及地形差异,导致的南北疆干旱呈现反相位变化的空间分布特征。新疆近50 a干旱时空变化整体上存在一致性,局域上又具有异质性。

Based on the meteorological data from 54 stations in Xinjiang during the period from 1963 to 2012,the values of the standardized precipitation and evapotranspiration index（ SPEI） at 12-month timescale were calculated. Meanwhile,the spatiotemporal variation of drought in recent 50 years was analyzed using the methods of linear regression,empirical mode decomposition（ EMD） and empirical orthogonal function（ EOF）. The results showed that the drought condition in Xinjiang in the past 50 years was changed significantly. A drying-to-wetting climate change occurred in Xinjiang since 1987. However,the decreased SPEI12 revealed that an obvious drying trend occurred in Xinjiang in the past decade. Temporally,there were three kinds of variation periods of drought including2-year period,6-year period and 24-year period. The first mode of EOF explained the consistent pattern of drought in whole Xinjiang,and the second mode of EOF reflected the wetting（ or drying） pattern in south Xinjiang and drying（ or wetting） pattern in north Xinjiang. The spatiotemporal variation of drought was overall consistency in whole Xinjiang but also heterogeneity at local scale.