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遥感技术具有覆盖范围广、空间分辨率高、重访周期短、数据获取快捷方便等优点,遥感干旱监测已经成为干旱监测的重要研究方向之一。詹志明(2005)、阿布(2004)等假设裸露土壤的光谱特征满足线性分布,在NIR-Red光谱特征空间中提出了垂直干旱指数(PDI),并在我国西北干旱区-宁夏固原地区进行了模型验证。为了进一步验证PDI在茂密植被覆盖条件下的可行性,选择长江中下游流域的典型灌区湖北漳河灌区作为研究区域,采用ETM+数据计算PDI,与2～5cm平均土壤水分相比较,结果表明:模型观测值变化曲线和实测土壤水分变化趋势保持一致,2～5cm平均土壤水分相关系数为0.76,与实测干旱指标基本吻合。PDI模型能够有效地反映地表覆盖和水热组合,简单实用,具有通用性和普适性,适宜于复杂下垫面条件下的遥感旱情监测。
Remote sensing technology has the advantages of wide coverage, high spatial resolution, short revisit period and quick and convenient data acquisition. Remote sensing drought monitoring has become one of the most important research directions in drought monitoring. Zhan Zhiming (2005) and Abu (2004) assumed that the spectral characteristics of exposed soil satisfy the linear distribution. The vertical drought index (PDI) was proposed in NIR-Red spectral feature space and was applied in the northwestern arid region of Ningxia Guyuan Model verification. In order to further verify the feasibility of PDI under the condition of dense vegetation cover, select the typical irrigation area in the middle and lower reaches of the Yangtze River as the study area, using ETM + data to calculate PDI, compared with the average soil moisture of 2 ~ 5cm, the results show that: The observed curve and the measured trend of soil moisture are consistent. The average soil moisture of 2 ~ 5 cm is 0.76, which is in good agreement with the measured drought index. The PDI model can effectively reflect the land cover and hydrothermal combination. It is simple and practical, universal and universally applicable. It is suitable for remote sensing drought monitoring under complicated underlying surface conditions.