Zhang Zhanjie, Wang Yong, Zhang Guang J, Xing Cheng, Xia Wenwen, Yang Mengmiao
Ministry of Education Key Laboratory for Earth System Modeling and Department of Earth System Science, Tsinghua University, Beijing, China.
Scripps Institution of Oceanography, La Jolla, CA, USA.
Nat Commun. 2024 Aug 26;15(1):7326. doi: 10.1038/s41467-024-51778-9.
Humid heat waves pose significant risks to human health and the ecosystem. Intuitively, rainfall often alleviates extreme humid heat. However, here we show that light rain often accompanies extreme humid heat, exacerbating its frequency and intensity, especially over arid and semi-arid regions compared to no rain and moderate-to-heavy rain cases. This is because light rain does not dramatically reduce solar radiation but increases near-surface humidity through enhanced surface evaporation. The water replenishment from light rain as well as a shallower planetary boundary layer is crucial for consecutive extremes where there are commonly sporadic drizzle days amidst several rain-free days. These extremes last longer than rain-free extremes. Current global climate models (GCMs) overestimate light rain. After reducing this bias in a GCM, underestimations of humid heat waves in energy-limited regions and overestimations in water-limited regions are largely alleviated. These findings underscore the underappreciated impact of light rain on extreme humid heat.
湿热浪对人类健康和生态系统构成重大风险。直观地说，降雨通常会缓解极端湿热天气。然而，我们在此表明，小雨常常伴随极端湿热天气，加剧其发生频率和强度，特别是在干旱和半干旱地区，与无雨及中到大雨的情况相比更是如此。这是因为小雨不会显著减少太阳辐射，反而会通过增强地表蒸发增加近地表湿度。小雨带来的水分补充以及较浅的行星边界层对于连续的极端天气至关重要，在这种情况下，通常在几个无雨日期间会有零星的毛毛雨天气。这些极端天气持续的时间比无雨极端天气更长。当前的全球气候模型（GCMs）高估了小雨的情况。在一个GCM中减少这种偏差后，能量受限地区对湿热浪的低估和水资源受限地区的高估在很大程度上得到缓解。这些发现凸显了小雨对极端湿热天气未得到充分认识的影响。
