Response of semi-arid vegetation to agricultural drought determined by indices derived from MODIS satellite

ABSTRACT Indices based on data from remote sensors play an important role in the characterization, mapping and monitoring of a drought event. Thus, the objective of this study was to monitor the dynamics of agricultural drought, through the response of vegetation, in the semi-arid region that comprises the state of Paraíba, Brazil, through MODIS satellite products applied to the VCI (vegetation condition index), TCI (temperature condition index) and VHI (vegetation health index) indices, and to evaluate the correspondence of VHI index with standardized precipitation index (SPI) and agricultural standardized precipitation index (aSPI). In this study, values of NDVI (normalized difference vegetation index) and LST (land surface temperature) - covering the period between 2010 and 2020 - were used to estimate VCI, TCI and VHI. In addition, the correspondence of VHI with SPI and aSPI was evaluated at the 12-month time scale, conducted using Pearson’s correlation analysis. Characteristics of a stressed vegetation predominated in the study region, due to irregularity of precipitation and high temperatures, confirming the possibility of detection of droughts through VHI, VCI and TCI, and that the indices detected remotely and through local data are strongly correlated in drought detection.摘要：基于遥感传感器数据构建的干旱监测指数在干旱事件的特征表征、空间制图与动态监测中发挥着重要作用。据此，本研究以巴西帕拉伊巴州所属半干旱区域为研究对象，借助MODIS卫星产品计算植被状态指数（VCI, Vegetation Condition Index）、温度状态指数（TCI, Temperature Condition Index）与植被健康指数（VHI, Vegetation Health Index），通过植被响应监测农业干旱的动态变化，并评估VHI指数与标准化降水指数（SPI, Standardized Precipitation Index）、农业标准化降水指数（aSPI, Agricultural Standardized Precipitation Index）的对应性。本研究采用2010至2020年的归一化差分植被指数（NDVI, Normalized Difference Vegetation Index）与地表温度（LST, Land Surface Temperature）数据估算VCI、TCI与VHI；此外，本研究在12个月时间尺度下开展Pearson相关分析，以此评估VHI与SPI、aSPI的相关性。受降水分布不规则与高温影响，研究区域内植被受胁迫的特征占主导，这证实了利用VHI、VCI与TCI开展干旱监测的可行性，同时表明遥感反演的干旱指数与本地数据计算的指数在干旱监测中具有显著强相关性。