典型农业干旱遥感监测指数的比较及分类体系

面对多种多样的农业旱情遥感监测指数,如何进行选取是目前遥感指数应用所面临的主要难题。该文以MODIS产品为遥感数据源,比较分析了13种典型的农业干旱遥感监测指数,建立了农业干旱遥感监测指数的分类体系,阐述了不同指数类型的适用范围。结果表明,多种遥感干旱指数对农业干旱的描述并非完全一致。不同指数利用不同的地表特征变化来描述农业干旱程度,是造成这种不一致的主要原因。据此,研究将典型农业干旱遥感监测指数分为4大类:土壤水分变化类、冠层温度变化类、植被水分变化类和作物形态及绿度变化类。其中第1类指数比较适宜于农业旱情预警及土壤干旱型农业旱情的监测,这类指数中修正的垂直干旱指数MPDI可以较好地反映表层土壤水分的变化,并适宜于时序变化监测。第2类指数不仅适宜于旱情预警,更适宜于旱情监测,这类指数中推荐选择基于LAI-LST特征空间的温度植被干旱指数TVDI;第3、4类指数,较适宜于农业旱灾的预警以及灾后评估,该文为农业干旱遥感监测指数的选取提供参考。

Comparisons and classification system of typical remote sensing indexes for agricultural drought

Various remote sensing indexes of agriculture drought were proposed at present, but it is hard to decide which one is the most appropriate. In this paper, an intercomparison among 13 remote sensed indexes for monitoring agricultural drought was performed using MODIS products. Then a classification system was constructed for these indexes, where the applicability of each class was demonstrated. The results indicated that these indexes were not exactly the same because different indexes used different features of land surface to represent agricultural drought. Consequently, these indexes were classified into four categories: reflecting soil moisture change, reflecting canopy temperature change, reflecting vegetation water content change, and reflecting crop form and greenness change. The first category was suitable for agricultural drought early warning and soil type agricultural drought monitoring, where the Modified Perpendicular Drought Index could effectively represent changes in the soil surface moisture, and was suitable for monitoring changes temporally. The second category was not only suitable for drought early warning, but also more suitable for drought monitoring, where the Temperature Vegetation Drought Index based on the LAI-LST feature space was recommended. The third and fourth categories were more suitable for early warning and assessment of agricultural drought disaster. The present paper provides a reference for the selection of remote sensing indexes for monitoring agricultural drought.