基于SPI指数的宁夏中部干旱带1960-2012年干旱特征研究

摘要

研究宁夏中部干旱带的干旱特征可为区域农牧业发展和防灾减灾提供科学决策依据.利用1960-2012年的各站点气象观测资料,计算标准化降水指数(SPI),并借助集合经验模态分解、功率谱分析和重新标度极差分析等方法,对近50年来的干旱特征和变化趋势进行了研究.研究结果表明,宁夏中部干旱带在1960-2012年间发生中旱以上的干旱事件达到了总干旱次数的30％以上;干旱波动周期的多尺度分解显示,该区域存在着0.5a尺度的轻旱,1 a尺度的中旱,3a尺度的重旱和10 a尺度的特旱;平均干旱强度的年际波动周期特征中,有平均超过65％的贡献来自于3.25-4 a左右的干旱周期波动,而平均超过14％的贡献来自于5.78-6.5 a左右的干旱周期波动;总体来看,宁夏中部干旱带的干旱趋势处于增强态势,且具有长程依赖性,即未来还将持续干旱,但不同季节的干旱趋势特征又表现出一定的差异.%With the purpose to provide scientific basis for regional agricultural development and disaster prevention and mitigation,by using the meteorological data from three in-situ stations during 1960 to 2012,the drought characteristics and variation trends in arid zone of middle Ningxia were studied by the method of standardized precipitation index (SPI),along with ensemble empirical mode decomposition (EEMD),power spectrum analysis and rescaled range analysis (R/S).The results showed that more than 30％ of drought events,which happened in arid zone of middle Ningxia from 1960 to 2012,were moderate or even more serious drought.The multi-scale decomposition of drought period showed that there existed four time scales for the change cycle of different intensities of drought,i.e.,0.5 a for mild drought,1 a for moderate drought,3 a for severe drought,and 10 a for extreme drought.The EEMD analysis showed that the inter-annual fluctuation of drought was mainly derived from a 3.25-4 a period which contributed more than 65％ to the whole variance,and followed by a 5.78-6.5 a period which contributed more than 14％.On the whole,the drought in arid zone of middle Ningxia is enhancing currently and this trend has a long-range dependence.Therefore,this region will keep a sustained drought in the future,but the characteristic of drought trend in various seasons is different.