Droughts are extreme meteorological and hydrological events having severe impacts on the natural environment and socioeconomic conditions of the affected region. Drought characterization is vital in planning, design, and management of water resources systems. Drought indices such as standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) are generally used as a tool for monitoring changes in drought conditions. The variability of monsoon droughts over India is significantly influenced by the tropical sea surface temperature anomalies. A major portion of the drought variability is influenced by the El Niño–Southern Oscillation (ENSO). Drought characterization for Indo Gangetic alluvial plain demonstrates the efficacy of the present work. The values of SPI and SPEI are found in all the possible ranges representing mild, moderate, and severe drought events in the study area. Most drought events are observed in Raebareli District, as both SPI and SPEI indices showed 27 and 23 severe events. Also, correlation is found between observed drought periods, ENSO episodes, and drought indices.

中文翻译：

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利用干旱指数和厄尔尼诺效应进行干旱表征

干旱是极端的气象和水文事件，对受影响地区的自然环境和社会经济状况造成严重影响。干旱特征对水资源系统的规划，设计和管理至关重要。诸如标准化降水指数（SPI）和标准化降水蒸散指数（SPEI）之类的干旱指数通常被用作监测干旱状况变化的工具。热带海表温度异常极大地影响了印度季风干旱的变化。厄尔尼诺-南方涛动（ENSO）影响着干旱变化的很大一部分。印度恒河冲积平原的干旱特征证明了本研究的有效性。在所有可能的范围内找到SPI和SPEI的值，代表研究区域的轻度，中度和严重干旱事件。SPI和SPEI指数均显示27和23个严重事件，因此在Raebareli区观察到大多数干旱事件。此外，在观测到的干旱时期，ENSO发作和干旱指数之间发现相关性。