In this study, the variability and trends of the outdoor thermal discomfort index (DI) in the Kingdom of Saudi Arabia (KSA) were analyzed over the 39-year period of 1980–2018. The hourly DI was estimated based on air temperature and relative humidity data obtained from the next-generation global reanalysis from the European Center for Medium-Range Weather Forecasts and in-house high-resolution regional reanalysis generated using an assimilative Weather Research Forecast (WRF) model. The DI exceeds 28°C, that is, the threshold for human discomfort, in all summer months (June to September) over most parts of the KSA due to a combination of consistently high temperatures and relative humidity. The DI is greater than 28°C for 8–16 h over the western parts of KSA and north of the central Red Sea. A DI of >28°C persistes for 7–9 h over the Red Sea and western KSA for 90% of summer days. The spatial extent and number of days with DI > 30°C, that is, the threshold for severe human discomfort, are significantly lower than those with DI > 28°C. Long-term trends in the number of days with DI > 28°C indicate a reduced rate of increase or even a decrease over some parts of the southwestern KSA in recent decades (1999–2018). Areas with DI > 30°C, in particular the northwestern regions of the Arabian Gulf and its adjoining regions, also showed improved comfort levels during recent decades. Significant increases in population and urbanization have been reported throughout the KSA during the study period. Analysis of five-years clinical data suggests a positive correlation between higher temperatures and humidity with heat-related deaths during the Hajj pilgrimage. The information provided herein is expected to aid national authorities and policymakers in developing necessary strategies to mitigate the exposure of humans to high levels of thermal discomfort in the KSA.

中文翻译：

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沙特阿拉伯王国户外热不适分析


本研究分析了 1980 年至 2018 年 39 年间沙特阿拉伯王国 (KSA) 户外热不适指数 (DI) 的变化和趋势。每小时 DI 是根据欧洲中期天气预报中心下一代全球再分析获得的气温和相对湿度数据以及使用同化天气研究预报 (WRF) 生成的内部高分辨率区域再分析来估计的模型。由于持续高温和相对湿度的共同作用，沙特阿拉伯大部分地区在整个夏季（6 月至 9 月）的 DI 超过 28°C，即人体不适的阈值。沙特阿拉伯西部地区和红海中部北部地区的 DI 持续 8-16 小时高于 28°C。 90% 的夏季，红海和沙特阿拉伯西部地区的 DI 为 >28°C，持续 7-9 小时。 DI> 30℃的空间范围和天数，即人体严重不适的阈值，明显低于DI> 28℃的空间范围和天数。 DI > 28°C 天数的长期趋势表明，近几十年来（1999 年至 2018 年）沙特阿拉伯西南部部分地区的增长速度有所放缓，甚至有所下降。近几十年来，DI > 30°C 的地区，特别是阿拉伯湾西北部地区及其毗邻地区，舒适度也有所提高。据报道，在研究期间，整个沙特阿拉伯的人口和城市化进程显着增加。对五年临床数据的分析表明，朝觐期间较高的温度和湿度与热相关死亡之间存在正相关关系。 本文提供的信息预计将有助于国家当局和政策制定者制定必要的战略，以减轻沙特阿拉伯境内人类遭受的高水平热不适。