广西降雨亏缺型骤旱的演变过程及时空分布特征

Characteristics of Spatiotemporal Distribution of Rainfall-Deficient Flash Drought in Guangxi

为研究降雨亏缺型骤旱在湿润地区的特性,以广西为研究区,在分析降雨亏缺型骤旱演变过程的基础上采用Mann-kendall,Hurst,BG分割算法、EEMD等分析了该型骤旱在广西的时空分布特征。结果表明:(1)该型骤旱在发生前期土壤湿度已明显偏低,在发生过程中,蒸散发、太阳辐射、气温等要素的变化特征显著相关,在发生后,土壤湿度会持续偏低1~5候;(2)在广西地区发生频率为1.0%~2.0%,发生面积主要集中在10%以下,持续时间主要集中在1~2候,在夏季多发且历时长;(3)在1979—2015年呈现出显著下降趋势,频次序列存在3.45 a的周期,且在1999年存在突变;(4)骤旱频次在桂南较高,历时在桂西南等地较长;而桂中地区,频次和历时呈现出显著下降趋势;(5)与季节性干旱同时发生的骤旱约有6%~15%,其中桂中及桂西南地区较高。该成果可为完善广西地区旱灾预警机制提供参考。

In order to study the characteristics of rainfall deficient type sudden drought in humid areas,Guangxi was selected as the study area.Based on the analysis of the evolution of rainfall-deficient flash drought,we analyzed the characteristics of spatiotemporal distribution of the drought in Guangxi from 1979 to 2015 by using Mann-kendall,Hurst,BG,EEMD.The results show that:(1)this type of flash drought in the early stage of the drought,soil moisture is obviously low,in the course of the drought,evapotranspiration,solar radiation,temperature and other factors are significantly correlated;after the occurrence of the drought,soil moisture will continue to be low for 5~25 days;(2)it occurs at the frequency of 1.0%~2.0%in Guangxi,the area is mainly concentrated below 10%,the duration is 5~10 days,which often occurs in summer and lasts for a long time;(3)it had shown the significant downward trend from 1979 to 2015,the frequency was a period of 3.45-year and had a mutation in 1999;(4)the frequency of flash drought is higher in southern Guangxi and the duration of flash drought is longer in southwestern Guangxi,while the frequency and duration of sudden drought show the significant downward trend in central Guangxi;(5)the frequency of simultaneous occurrence of flash drought and seasonal drought in the region are between 6%and 15%.These results can provide reference for improving the early warning of drought in Guangxi.