Abstract：
Agriculture is the most sensitive sector which has largely been affected by the impacts of drought. The study aims to detect and characterize agricultural droughts using MODIS-based multiple indices in North Wollo, Ethiopia. Two Moderate Resolution Imaging Spectroradiometer (MODIS) datasets (MOD13Q1 and MOD11A2) for the period 2000 to 2019 were used to generate Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST). Accordingly, NDVI anomaly, Vegetation Condition Index (VCI), Temperature Condition Index (TCI), and Vegetation Health Index (VHI) were computed to characterize agricultural droughts during the crop growing season. Both the NDVI anomaly and VCI confirmed that there was no single drought-free year in the area throughout the study period. TCI showed relatively exaggerated drought stress than the other indices. However, VHI indicated lower area coverage and a lower level of stress than its aggregates (VCI and TCI). Specifically, 2002, 2004, 2009, 2010, and 2015 were all identified as severe drought years, where over 60% of the area was affected by droughts. Results of the regression analysis indicated that VCI, TCI, and VHI were having significant positive trends with precipitation in the majority of the districts. Using the aggregated drought frequency of each index, 13.5, 73.7, and 12.8% of the area were under moderate, high, and extremely high levels of agricultural drought occurrence, respectively, and the likelihood of implied risks. Therefore, all the districts of North Wollo were affected by persistent drought stress. Such drought recurrences have the potential to impose significant impacts on the agro-based livelihoods of the local community demanding ongoing drought monitoring and the application of effective early warning systems.
摘要：
农业是最敏感的部门，在很大程度上受到干旱影响。该研究旨在在NorthWollo使用基于MODIS的多个指数来检测和表征农业干旱，埃塞俄比亚。2000年至2019年期间的两个中分辨率成像光谱辐射计（MOD13Q1和MOD11A2）数据集用于生成归一化植被指数（NDVI）和地表温度（LST）。因此，NDVI异常，植被状况指数(VCI),温度条件指数(TCI),计算和植被健康指数（VHI）以表征作物生长季节的农业干旱。NDVI异常和VCI均证实，在整个研究期间，该地区没有单一的干旱年份。TCI比其他指标表现出相对夸大的干旱胁迫。然而,VHI表示比其聚集体(VCI和TCI)更低的面积覆盖率和更低的应力水平。具体来说,2002年、2004年、2009年、2010年和2015年都被确定为严重干旱年，超过60%的地区受到干旱的影响。回归分析结果表明，VCI，TCI和VHI与大多数地区的降水呈显着的正趋势。使用每个指数的累积干旱频率，13.5、73.7和12.8％的面积在中度以下，高,和极高水平的农业干旱发生，分别,以及隐含风险的可能性。因此,北Wollo的所有地区都受到持续干旱胁迫的影响。这种干旱的复发有可能对当地社区的农业生计产生重大影响，要求持续进行干旱监测和应用有效的预警系统。
