基于SPEI及游程理论的云贵地区1960—2014年干旱时空变化特征

The temporal variation characteristics of drought in Yunnan-Guizhou area during 1960 to 2014 based on SPEI and runlength theory

基于云贵地区49个气象站点1960—2014年的逐月气象数据,计算得到云贵地区季尺度及年尺度的标准化降水蒸散发指数序列,结合游程理论及经验正交(EOF)等方法,揭示云贵地区干旱的时空变化特征.研究结果表明:(1)云贵地区气候呈现逐渐变干的趋势,且年尺度和季尺度在21世纪初均出现由湿转干的迹象.(2)同一干旱历时条件下,不同等级干旱发生的频率不同,等级越小发生频率越高,反之亦然.同一等级的干旱发生频率随干旱历时长度的增加而减小.(3)在历时2~5个月的干旱事件中,云南省的干旱重现期均小于贵州省,即云南省发生干旱事件较贵州省频繁.27°N以北地区的干旱重现期较长,干旱事件发生频率较小.(4)对云贵地区近55a的SPEI进行经验正交(EOF)分析知,EOF展开第1模态反映的是季风系统控制下的云贵地区旱涝一致性变化情况,21世纪后,云贵地区普遍处于干旱状态;EOF展开第2模态反映的是受乌蒙山阻隔,东西两侧干旱呈现反相位变化的空间分布特征.该研究对于认识和把握区域气候干旱趋势与规律,提高区域干旱预警能力,保证粮食安全和生态经济稳定有重要的现实意义.

Based on the monthly meteorological data from 49 stations in Yun-Gui area during the period from 1960 to 2014,the values of the standardized precipitation and evapotranspiration index at season and year scale were calculated.Meanwhile,the variation of drought was analyzed using the methods of the run-length analysis theory and empirical orthogonal function(EOF).The results show that:(1)The Yun-Gui area showed a trend of gradually dry,and a wetting-to-drying climate change since the 21 st century.(2)Under the same drought the occurring probability will be different depending on different dry grade,the lower the dry grade,the greater its probability,and vice versa.For the same grade of drought,the longer the drought lasted,the lower of its probability.(3)The return period of drought in Yunnan is shorter than that in other area,and that at the junction of Yun-Gui area is the longest.(4)The first mode of EOF explains the consistent pattern of drought in whole Yun-Gui area,and the second mode of EOF reflects the drying(or wetting)pattern in Yunnan province and wetting(or drying)in Guizhou province,because of the terrain differences and that WuMeng mountain cuts off the Yun-Gui area.