Abstract Spatial and temporal variability of drought in Oman was assessed for the period 1979–2014 using the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) at both seasonal (3-month) and annual (12-month) timescales. Changes in drought characteristics (e.g. frequency, duration, intensity, severity, and spatial extent) were detected for six distinct climatic regions delineated using a Principal Component Analysis (PCA). Results suggest a statistically significant increase in the frequency and severity of drought during the past four decades. Nonetheless, drought exhibited pronounced decadal variability, with more frequent and severe droughts occurring after 1997/1998. Also, results demonstrate that the areas influenced by extreme and very extreme droughts witnessed a statistically significant increase on the order of 0.13% and 0.18%/decade, respectively, compared to −0.06%/decade for the areas impacted by mild droughts. Spatially, there has been a prevalent drying trend in central and eastern regions of Oman, while a tendency towards wetter conditions was observed in northern Oman (especially in the Batinah plain). This study also investigates the time-varying dependency between climatic drivers of drought and large-scale circulation patterns using the cumulative annual mean (CAM) method. Results indicate an acceleration of drying after 1997/1998, mainly due to the warming sea surface temperature (SST) anomalies over the Atlantic Ocean in recent decades and also the shift of the Pacific Ocean circulation patterns (e.g. PDO and El Nino) from the positive to the negative mode at the end of the 1990s. These configurations are favorable for significant changes in the thermodynamic drivers of drought (i.e. air temperature and relative humidity), but have less influence on aerodynamic drivers (i.e. wind speed). The significant temperature rise in recent decades, combined with a significant decline of rainfall and relative humidity, can explain the prolonged drought episode lasting from 1998 to 2014. A comprehensive assessment of drought variability in a poorly-studied water-stressed region like Oman is of particular concern for stakeholders and policy-makers. This study provides meaningful conclusions and a basis for water resources management, agricultural and energy production, ecological protection, and contribute to more reliable drought mitigation strategies at the regional and national scales.

中文翻译：

---

过去 40 年阿曼气象干旱加剧的证据

摘要 使用标准化降水指数 (SPI) 和标准化降水蒸散指数 (SPEI) 在季节性（3 个月）和年度（12 个月）时间尺度上评估了 1979-2014 年阿曼干旱的时空变异性。 . 对使用主成分分析 (PCA) 描绘的六个不同气候区域检测到干旱特征的变化（例如频率、持续时间、强度、严重程度和空间范围）。结果表明，在过去的 40 年里，干旱的频率和严重程度在统计上显着增加。尽管如此，干旱表现出明显的年代际变异性，在 1997/1998 年之后发生更频繁和更严重的干旱。还，结果表明，受极端和非常极端干旱影响的地区分别以 0.13% 和 0.18%/十年的统计显着增加，而受轻度干旱影响的地区则为 -0.06%/十年。在空间上，阿曼中部和东部地区普遍存在干燥趋势，而在阿曼北部（尤其是巴提拿平原）则观察到更潮湿的趋势。本研究还使用累积年平均 (CAM) 方法调查了干旱气候驱动因素与大尺度环流模式之间的时变依赖性。结果表明，1997/1998 年之后干旱加速，主要是由于近几十年来大西洋上空的海面温度 (SST) 异常变暖以及太平洋环流模式的转变（例如 G。PDO 和厄尔尼诺现象）在 1990 年代末从正模式转为负模式。这些配置有利于干旱的热力学驱动因素（即气温和相对湿度）的显着变化，但对空气动力学驱动因素（即风速）的影响较小。近几十年来气温显着上升，加上降雨量和相对湿度显着下降，可以解释 1998 年至 2014 年持续的长期干旱事件。对像阿曼这样研究不足的缺水地区干旱变异性的综合评估是利益相关者和政策制定者的特别关注。本研究为水资源管理、农业和能源生产、生态保护、