基于SPEI_PM分析广西干旱时空变化及其与ENSO的关系

Spatio-temporal Variation of Guangxi Drought Based on the SPEI_PM and Its Correlation with ENSO

利用广西19个气象站点1961-2020年月值气象数据,基于Penman-Monteith蒸散模型计算标准化降水蒸散发指数(SPEI_PM),通过线性倾向估计、Mann-Kendall趋势检验、互相关函数、交叉小波变换和小波相干等方法,分析广西气象干旱的时空变化特征,探究厄尔尼诺-南方涛动(ENSO)与广西气象干旱的关联性,以期为干旱预警与防治提供依据。结果表明:1961−2020年广西夏季、秋季和年SPEI_PM整体上呈显著线性上升趋势,气候具有湿润化趋势。全区年际和季节尺度干旱发生频率均以轻旱和中旱为主,重旱和特旱发生频率较低。春季干旱集中发生在桂中部地区,夏季集中在桂西南地区,秋季集中在桂东南和桂东北地区,冬季干旱全区都有分布,而年尺度干旱集中在桂东北地区。广西干旱站次比有明显的年代特征,全区大范围发生旱情尤其是重旱和特旱主要集中在1960s、1970s和2000s。ENSO事件对广西气象干旱的影响具有显著的空间异质性,海洋尼诺指数(ONI)与桂东北和桂东南地区的干旱相关性最高,其次是桂西北地区,而沿海地区和桂西南大部分地区与ONI没有显著相关性。作为桂东北地区的典型代表,桂林气象站的SPEI-3与ONI在1962-1976年和1990-2019年分别表现出16~48个月和12~64个月的年际主共振周期。

Using monthly data from 19 meteorological stations in Guangxi Zhuang Autonomous region from 1961 to 2020,this study calculated the standardized precipitation evapotranspiration index(SPEI)based on the Penman-Monteith evapotranspiration model(SPEI_PM).The temporal and spatial variation of meteorological drought were analyzed via linear tendency estimation,and Mann-Kendall trend test.The correlation between El Niño-Southern Oscillation(ENSO)and meteorological drought in Guangxi was also explored by cross-correlation function,cross wavelet transform and wavelet coherence.The values for summer,autumn,and annual SPEI_PM from 1961 to 2020 exhibited a significant linear trend of increasing wetness over time.Annual and seasonal droughts throughout the region were predominately mild and moderate,with less frequent severe and extreme droughts.Spring droughts were concentrated in the central part of the region,summer droughts in the southwest,autumn droughts in the southeast and northeast,and winter droughts spread throughout the region.Annual droughts were concentrated in the northeast.The rate of drought occurrence as measured by the stations in Guangxi exhibited a distinctly chronological character.Large-scale droughts(especially severe and extreme droughts)across the entire region occurred most often in the 1960s,1970s,and 2000s.The impact of ENSO on the meteorological drought in Guangxi was characterized by spatial heterogeneity.Correlation between the ocean Niño index(ONI)and meteorological drought was highest in the northeast and southeast,as well as the northwest.There was no significant correlation between drought and ONI in coastal areas and most southwestern parts of the region.As a typical example from meteorological stations in northeastern Guangxi,SPEI-3 and ONI at the Guilin Meteorological station showed interannual oscillation cycles of 16−48 months in the period 1962−1976,and 12−64 months in the period 1990−2019.These results can serve as a useful reference for future drought forecasting and assessment in Guangxi.