Abstract
Heat events may be humid or dry. While several indices incorporate humidity, such combined indices obscure identification and exploration of heat events by their different humidity characteristics. The new HadISDH.extremes global gridded monitoring product uniquely provides a range of wet and dry bulb temperature extremes indices. Analysis of this new data product demonstrates its value as a tool for quantifying exposure to humid verses dry heat events. It also enables exploration into “stealth heat events”, where humidity is high, perhaps enough to affect productivity and health, while temperature remains moderate. Such events may not typically be identified as “heat events” by temperature-focused heat indices. Over 1973–2022, the peak magnitude of humid extremes (maximum daily wet bulb temperature over a month; TwX) for the global annual mean increased significantly at 0.13 ± 0.04°C (10 yr)−1, which is slightly slower than the global annual mean Tw increase of 0.22± 0.04°C (10 yr)−1. The frequency of moderate humid extreme events per year (90th percentile daily maxima wet bulb temperature exceedance; TwX90p) also increased significantly at 4.61 ± 1.07 d yr−1 (10 yr)−1. These rates were slower than for temperature extremes, TX and TX90p, which respectively increased significantly at 0.27 ± 0.04°C (10 yr)−1 and 5.53 ± 0.72 d yr−1 (10 yr)−1. Similarly, for the UK/Europe focus region, JJA-mean TwX increased significantly, again at a slower rate than for TX and mean Tw. HadISDH.extremes shows some evidence of “stealth heat events” occurring where humidity is high but temperature remains more moderate.
摘要
热事件可能是潮湿或干燥的. 虽然一些指数包含了湿度信息, 但这些综合指数由于其不同的湿度特征而模糊了对热事件的识别和进一步探索. 针对这一问题, 本文提供了包含一系列湿球和干球极端指数的新的全球格点化监测产品HadISDH.extremes, 这一新的数据产品在量化湿热和干热事件暴露度等方面具有潜在价值. 该数据产品同样可用于分析“隐形热事件”, 即温度并不十分极端, 但湿度已经高到可能足以影响生产和健康的情况, 这类事件通常不会被基于温度的热指数识别为“热事件”. 在1973–2022年间, 年平均的全球极端湿热事件峰值(一个月内日湿球温度的最大值; TwX)以0.13±0.04°C(10 yr)−1的速率显著上升, 略缓于年平均的全球湿球温度(Tw)的0.22±0.04°C(10 yr)-1. 每年中等极端湿热事件的频次(超过日最大湿球温度90%分位数的频次; TwX90p)以4.61±1.07 d yr−1 (10 yr)−1的速率显著增加, 这一速率低于同样显著增加的极端温度指数TX(0.27±0.04°C(10 yr)−1)和TX90p(5.53±0.72 d yr−1 (10 yr)−1). 类似地, 聚焦于英国/欧洲, 6–8月平均的TwX显著增加, 同样慢于TX和平均Tw. HadISDH.extremes揭示了一些关于“隐形热事件”的证据.
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Acknowledgements
This work and its contributors (Kate WILLETT) were supported by the UK-China Research & Innovation Partnership Fund through the Met Office Climate Science for Service Partnership (CSSP) China as part of the Newton Fund.
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Article Highlights
• HadISDH.extremes is a new monitoring product for exploring large-scale, long-term features of humid and dry heat events.
• HadISDH.extremes shows significantly increasing humid heat extreme magnitude and frequency, but at a slower rate than for dry heat.
• HadISDH.extremes shows that increasing extreme heat magnitude is changing more slowly than mean temperature and humidity.
This paper is a contribution to the 2nd Special Issue on Climate Science for Service Partnership China.
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Willett, K.M. HadISDH.extremes Part II: Exploring Humid Heat Extremes Using Wet Bulb Temperature Indices. Adv. Atmos. Sci. 40, 1968–1985 (2023). https://doi.org/10.1007/s00376-023-2348-7
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DOI: https://doi.org/10.1007/s00376-023-2348-7