甘肃省河东地区干旱遥感监测指数的对比和应用

Comparison and Application of Drought Monitoring Remote Sensing Indices in the Hedong Area of Gansu,China

干旱是影响甘肃省河东地区农业生产的主要气象灾害之一。如何在众多的干旱遥感监测指数中选择适宜的指数是干旱遥感监测工作面临的主要问题。利用研究区30个农业气象站观测的不同深度土壤相对湿度和对应的MODIS数据,分析了7种典型干旱遥感监测指数(AVI、NDWI、VCI、PDI、MPDI、VSWI和MEI)的构建原理和模拟结果,并选择适宜的干旱遥感监测指数对2006年甘肃省河东地区干旱情况的时空分布做了动态监测。结果表明:7种干旱遥感监测指数均能反映研究区土壤湿度的时空变化特征;各干旱遥感监测指数对土壤水分监测的最佳深度为20cm,其次为10cm。从相关系数来看,PDI、MPDI指数对春季,VSWI、NDWI指数对夏季的土壤相对湿度有较好的监测结果;MEI指数对秋季土壤相对湿度模拟效果较差,其余指数对秋季模拟效果均较好;根据各指数与20cm处土壤相对湿度的相关系数,结合各指数的构成原理,春季选择PDI和MEI,夏季选择VSWI和NDWI,秋季选择PDI和MPDI,分别对2006年甘肃省河东地区干旱情况进行监测。通过考虑各等级出现的频率,同时兼顾土壤相对湿度,评定各指数干旱等级。监测结果显示,庆阳市北部连续出现春旱、春末夏初旱、伏旱和秋旱,陇中北部和庆阳市北部旱情严重。

Drought is one of the major meteorological disasters which affect the agricultural production in the Hedong Area,Gansu,China.Various remote sensing indices of agriculture drought are proposed,but it is difficult to decide which one is more appropriate.Analysis on the construction principle and simulation results of seven remote sensing indices was made with the relative soil moisture and MODIS data in different depth from30 agriculture meteorological stations in the studied area.Then the appropriate remote sensing indices were chosen to monitor the temporal and spatial distribution of drought in the area in 2006.The results showed that the seven remote sensing indices could reflect the spatiotemporal variation of soil moisture in the studied area.The best depth for monitoring soil moisture was 20 cm by the seven remote sensing indices,followed by 10 cm.A dynamic change of relative soil moisture during different seasons showed that monitoring effects of PDI and MPDI were good in spring,VSWI and NDWI were good in summer,and in addition to MEI,the other indexes were good in autumn.According to the correlation coefficients between the indexes and relative soil moisture,we selected PDI and MEI in spring,VSWI and NDWI in summer and PDIand MPDI in autumn to monitor the drought in Hedong Area in 2006.By considering the frequency of each drought grade and the relative soil moisture,we evaluated the drought grade for each indexes.Monitoring results showed that the drought occurred continuously in spring,late spring and early summer,midsummer,and autumn in the northern part of Qingyang.The continuous drought was very serious in the northern part of Longzhong and Qingyang.