基于植被状态指数的县域冬小麦干旱时空变化特征分析

Temporal and Spatial Analysis of Winter Wheat Drought on County Scale Based on Vegetation Condition Index

[目的]分析县域冬小麦干旱的时空异质性,为抗旱减灾提供辅助决策支持。[方法]基于GF1,Landsat,Sentinel-2等中高分辨率遥感数据,选取植被状态指数(Vegetation Condition Index,VCI)作为干旱监测指标,计算2011—2021年禹州市冬小麦VCI,逐年分析禹州市冬小麦干旱分布情况,并通过变异系数、线性趋势法、重心迁移和标准差椭圆等方法,对禹州市冬小麦干旱的稳定性、变化趋势、时空变化等特征进行了多维度分析。[结果](1)空间上,2011—2021年禹州市冬小麦干旱主要分布在北部和西部的山岗丘陵区,干旱面积和干旱强度由平原区向山岗区逐渐延展扩大;变异系数与变化百分率均值分别为0.62,13.12%,冬小麦干旱稳定性与变化趋势空间分布一致性高;重心迁移轨迹总距离和标准差椭圆扁率从无旱到重旱逐渐变小,标准差椭圆面积逐渐变大,表明干旱空间分布由集中趋于分散;(2)时间上,禹州市冬小麦每年都有轻旱发生,中旱和重旱平均2~4年发生一次,2012—2014年连续3年旱情较重,中旱和重旱总占比均超过35%,其次为2016年和2018年。[结论]近11年来禹州市冬小麦干旱总体上呈现向好的发展态势,大部分区域冬小麦旱情改善较为明显,对于旱情严重且不稳定区域需加强防控力度。

[Objective]By the spatial and temporal heterogeneity of winter wheat drought in the county was analyzed to provide auxiliary decision support for drought resistance and disaster reduction.[Methods]The vegetation condition index(VCI)was selected as the drought monitoring index.Based on GF1,Landsat,Sentinel-2 and other high resolution remote sensing data,the VCI of winter wheat in Yuzhou City from 2011 to 2021 was calculated.The variation coefficient,linear trend method,center of gravity migration and standard deviation ellipse were used to analyze the drought characteristics of winter wheat in Yuzhou City,such as stability,change trend,spatial and temporal changes.[Results](1)From the spatial point of view,the drought of winter wheat in Yuzhou City mainly distributed in the northern and western hillock areas from 2011 to 2021,and the drought area and drought intensity gradually expanded from plain area to hillock area.(2)The mean value of variation coefficient and variation percentage were 0.62 and 13.12%,respectively.The spatial distribution of drought stability and variation trend of winter wheat was highly consistent.(3)The total distance of the center of gravity migration trajectory and the standard deviation ellipse flat rate gradually decreased from no drought to severe drought,and the standard deviation ellipse area gradually increased,indicating that the spatial distribution of drought tended to scatter from concentration.(4)In terms of time,mild droughts occurred every year in period of winter wheat growth in Yuzhou City,with moderate and severe droughts occurring in an average of 2 to 4 years.Droughts were severe for three consecutive years in 2012—2014,with moderate and severe droughts accounting for more than 35 percent,followed by 2016 and 2018.[Conclusion]During the 11 years,the drought of winter wheat in Yuzhou City generally showed a good development trend,and the drought in the period of winter wheat growth in most regions was improved significantly,for severe drought and unstable areas,prevention and control should be strengthened.