Increased heat risk in wet climate induced by urban humid heat
Increased heat risk in wet climate induced by urban humid heat
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DOI：
10.1038/s41586-023-05911-1
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发表时间：
2023-04
期刊：
影响因子：
64.8
通讯作者：
Keer Zhang;Chang Cao;H. Chu;Lei Zhao;Jiayu Zhao;X. Lee
中科院分区：
文献类型：
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作者：
Keer Zhang;Chang Cao;H. Chu;Lei Zhao;Jiayu Zhao;X. Lee
城市通常比邻近的农村地区更温暖，这种现象被称为城市热岛（UHI）。通常伴随着城市热岛效应的是另一种称为城市干岛（UDI）的现象，即城市土地的湿度低于周围农村土地的湿度。UHI加剧了城市居民的热应激，而UDI可能反而提供缓解，因为人体可以通过出汗在较低湿度下更好地科普炎热条件。通过湿球温度（Tw）的变化测量的城市热岛和城市热岛指数之间的相对平衡是城市气候中人类热应激的一个关键但在很大程度上未知的决定因素。在这里，我们表明，Twis减少城市在干燥和适度潮湿的气候，其中UDI超过抵消城市热岛，但增加在潮湿的气候（夏季降水量超过570毫米）。我们的研究结果来自对世界各地城市和农村气象站数据的分析以及城市气候模型的计算。在潮湿气候中，城市白天Twis比夏季ruralTwin高0.17 ± 0.14摄氏度（平均值± 1标准差），主要是因为城市空气中的动力混合较弱。这个增量很小，但由于高本底Twin潮湿气候，在目前的气候条件下，它足以造成城市居民每年夏季2至6个额外的危险热应激日。预计未来极端湿热的风险将增加，这些城市效应可能进一步放大风险。
Cities are generally warmer than their adjacent rural land, a phenomenon known as the urban heat island (UHI). Often accompanying the UHI effect is another phenomenon called the urban dry island (UDI), whereby the humidity of urban land is lower than that of the surrounding rural land, –. The UHI exacerbates heat stress on urban residents,, whereas the UDI may instead provide relief because the human body can cope with hot conditions better at lower humidity through perspiration,. The relative balance between the UHI and the UDI—as measured by changes in the wet-bulb temperature (Tw)—is a key yet largely unknown determinant of human heat stress in urban climates. Here we show thatTwis reduced in cities in dry and moderately wet climates, where the UDI more than offsets the UHI, but increased in wet climates (summer precipitation of more than 570 millimetres). Our results arise from analysis of urban and rural weather station data across the world and calculations with an urban climate model. In wet climates, the urban daytimeTwis 0.17 ± 0.14 degrees Celsius (mean ± 1 standard deviation) higher than ruralTwin the summer, primarily because of a weaker dynamic mixing in urban air. ThisTwincrement is small, but because of the high backgroundTwin wet climates, it is enough to cause two to six extra dangerous heat-stress days per summer for urban residents under current climate conditions. The risk of extreme humid heat is projected to increase in the future, and these urban effects may further amplify the risk.