The Simplified Wet Bulb Globe Temperature (sWBGT) is widely used in heat stress assessments for climate-change studies, but its limitations have not been thoroughly explored. Building on recent critiques of sWBGT's use for current climate on global scale, this study examines sWBGT's biases using dynamically-downscaled sub-daily climate projections under multiple future emission scenarios. The analysis is aimed at understanding caveats in the application of sWBGT and the uncertainties in existing climate change analysis dependent on sWBGT. Results indicate sWBGT's biases are heavily influenced by local near-surface air temperature, with overestimation of heat stress in East Asia regions, particularly hot and humid areas, due to static assumptions of radiation and wind speed. This overestimation is amplified in warmer climates, leading to exaggerated projected heat stress increases in future. In contrast, underestimations are found for heat stress levels attributed to low wind speeds and strong radiations, such as over the Tibetan Plateau and certain extreme events. Additionally, sWBGT underestimates variability in extreme heatwave events compared to WBGT in both current and future climates, irrespective of overestimation in absolute heatwave intensities. This study emphasizes the limitations of sWBGT, especially in future warmer climates. Importance of sub-daily data for capturing daily maximum heat stress level and reflecting diurnal variations in different components is also discussed. In conclusion, we recommend using Liljegren's model (i.e., physics-based calculation) with high-resolution sub-daily climate data for more accurate outdoor heat stress assessments in climate change studies.

中文翻译：

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在温暖的气候下放大了简化的湿球温度与基于物理的湿球温度之间的差异


简化湿球温度（sWBGT）广泛用于气候变化研究的热应激评估，但其局限性尚未得到彻底探讨。基于最近对 sWBGT 在全球范围内用于当前气候的批评，本研究利用在多种未来排放情景下动态缩小的次日气候预测来检验 sWBGT 的偏差。该分析旨在了解 sWBGT 应用中的注意事项以及依赖于 sWBGT 的现有气候变化分析的不确定性。结果表明，sWBGT 的偏差很大程度上受到当地近地表气温的影响，由于辐射和风速的静态假设，东亚地区，特别是炎热和潮湿的地区的热应力被高估。这种高估在气候温暖的情况下会被放大，导致未来热应激的预测被夸大。相比之下，由于低风速和强辐射（例如青藏高原和某些极端事件）导致的热应激水平被低估。此外，与 WBGT 相比，sWBGT 低估了当前和未来气候下极端热浪事件的变异性，无论绝对热浪强度是否被高估。这项研究强调了 sWBGT 的局限性，特别是在未来气候变暖的情况下。还讨论了次日数据对于捕获每日最大热应激水平和反映不同成分的日变化的重要性。总之，我们建议使用 Liljegren 模型（即基于物理的计算）和高分辨率次日气候数据，以便在气候变化研究中进行更准确的室外热应激评估。