标题： 生理活性植被在湿润城市气候中逆转其降温效应 显示英文标题

标题： Physiologically Active Vegetation Reverses Its Cooling Effect in Humid Urban Climates

摘要： 为城市降温的绿色努力成效不一，因为同样能降低地表温度的植被也可能加剧空气中的炎热感。 先前的研究已将湿热识别为一种日益增长的城市危害，但生理活跃植被如何调控降温与湿度积累之间的权衡仍知之甚少，导致缓解政策和设计大多缺乏指导。 在此，我们量化了植被结构和功能对热指数（HI）的影响，HI是138个印度城市中温度和湿度的综合指标，这些城市涵盖了热带稀树草原、半干旱草原和湿润亚热带气候，并覆盖了密集的城市核心和半城市环带。 使用一种考虑极端情况的1公里HI重建方法，以及一个结合SHapley Additive Explanations（SHAP）和Accumulated Local Effects（ALE）的可解释机器学习框架，我们隔离了植被-气候的相互作用。 当EV I >= 0.4且LAI >= 0.05时，降温效果通常会增强，但当EV I >= 0.5、LAI >= 0.2且fPAR >= 0.5时，联合高值区域开始转向升温，而在潮湿、密集的核心区域，当fPAR >= 0.25时，升温现象更早出现。 在这些环境中，高度生理活跃的植被使近地面湿度上升的速度快于其去除热量的速度，从而逆转其降温效果并加剧感知到的热应激。 这些发现确立了植被驱动降温的气候限制，并为促进公平和抗热城市的气候特定绿化策略提供了定量阈值。 显示英文摘要

摘要： Efforts to green cities for cooling are succeeding unevenly because the same vegetation that cools surfaces can also intensify how hot the air feels. Previous studies have identified humid heat as a growing urban hazard, yet how physiologically active vegetation governs this trade-off between cooling and moisture accumulation remains poorly understood, leaving mitigation policy and design largely unguided. Here we quantify how vegetation structure and function influence the Heat Index (HI), a combined measure of temperature and humidity in 138 Indian cities spanning tropical savanna, semi-arid steppe, and humid subtropical climates, and across dense urban cores and semi-urban rings. Using an extreme-aware, one kilometre reconstruction of HI and an interpretable machine-learning framework that integrates SHapley Additive Explanations (SHAP) and Accumulated Local Effects (ALE), we isolate vegetation-climate interactions. Cooling generally strengthens for EVI >= 0.4 and LAI >= 0.05, but joint-high regimes begin to reverse toward warming when EVI >= 0.5, LAI >= 0.2, and fPAR >= 0.5,with an earlier onset for fPAR >= 0.25 in humid, dense cores. In such environments, highly physiologically active vegetation elevates near-surface humidity faster than it removes heat, reversing its cooling effect and amplifying perceived heat stress. These findings establish the climatic limits of vegetation-driven cooling and provide quantitative thresholds for climate-specific greening strategies that promote equitable and heat-resilient cities.