Building Resilient Cities for Heat Waves

正如气专委预测的(与其他极端天气相比，如降水、寒冷、极端天气相比更有信心)，热浪(HWS)在未来几十年可能发生得更频繁、强度更高、持续时间更长。城市在建筑形式、材料和密集的人类活动方面与周围环境不同。这些差异导致了众所周知的城市热岛效应，即城市往往比周围环境更温暖。城市热岛效应加剧了水暖，使城市更容易受到水暖的影响，从而给城市居民带来了更大的热压力。这对于那些容易患上与高温相关的疾病的居民尤其令人担忧，因为在不久的将来，随着越来越多的人生活在城市环境中，全球范围内的HW情景将会加剧。因此，为HWS建设有弹性的城市需要紧急关注。复原力是“一个社区或社会在面临危险时的适应能力”。要为HWS建设有弹性的城市，关键是要了解城市在不同情景下对HWS的反应：随着气候变化，气候极端可能也会发生变化，这会迫使城市系统通过“剂量-反应”功能，从而导致不同的生物物理影响。气候与城市生物物理影响之间的“剂量-反应”函数本质上是由城市-大气相互作用决定的，其中地表能量平衡是更好地理解的关键之一。在本文中，我将使用模拟和观测方法来研究城市-大气相互作用以及在HWS下的城市地表能量平衡。为了更好地理解热浪下的城市-大气相互作用，将开发一个适应性工具--城市气候分析框架(ANUC)。与其他流行的基于数值的城市气候模型相比，ANUC框架具有各种气候变量的解析表达式而不是数值表达式，这使该框架从昂贵的计算负担中解脱出来，并促进了对尽可能多的硬件场景的探索。这些观测将通过在世界各地建立城乡通量观测对来强调地表能量平衡的城乡对比，其结果有望概括不同气候下地表能量平衡的城乡特征。基于ANUC框架和全球城乡SEB的特点，我将通过进行许多ANUC模拟来证明在当前和未来气候的HWS下缓解热压力的不同工程方法的有效性。这项研究将形成对HWS下城市和大气之间的动态的更好的理解，并将评估城市在当前和未来气候下缓解策略的有效性，这将有助于建立未来具有HW弹性的城市。

As projected by IPCC (with higher confidence compared to other weather extremes e.g., precipitation, cold, extremes), heat waves (HWs), excessively hot periods, are likely to occur more frequently, with higher intensities, and with longer duration, in the coming decades. Cities differ from their surroundings in terms of built forms, materials, and intensive anthropogenic activities. These differences result in the well-known urban heat island (UHI) effect, whereby cities are often warmer than their surroundings. HWs are exacerbated by the UHI effect and cause cities to be more vulnerable to HWs resulting in greater thermal stresses for urban residents. This is of particular concern for those residents susceptible to heat-related illness, given the intensified HW scenarios in the near future, and worldwide with more people living in urban environments. As such, building resilient cities for HWs warrants urgent attention. Resilience is "the capacity of a community or society to adapt when exposed to a hazard". In order to build resilient cities for HWs, the key is in understanding the responses of cities to HWs under varying scenarios: as climate changes, the climate extremes may also vary, which forces the urban systems through a "dose-response" function and subsequently leads to different biophysical impacts. The "dose-response" functions between climate and biophysical impacts in cities are essentially determined by the urban-atmospheric interactions, where the surface energy balance is one of the keys to greater understanding.In this Fellowship, I will employ both modelling and observational approaches to investigate the urban-atmospheric interactions as well as the urban surface energy balance under HWs. An adaptable tool, the analytical urban climate (ANUC) framework, will be developed for better understanding the urban-atmospheric interactions under heat waves. Compared with other popular numerically-based urban climate models, the ANUC framework features analytical rather than numerical expressions of various climate variables, which relieves the framework from expensive computational burdens and facilitates the exploration of as many HW scenarios as possible. The observations will emphasise the urban-rural contrasts in surface energy balance by constructing urban-rural flux observation pairs worldwide, the results of which are expected to allow generalisation of the urban-rural characteristics of the surface energy balance under different climates. Based upon the ANUC framework and the global urban-rural SEB characteristics, I will justify the effectiveness of different engineering approaches for mitigating thermal stress under HWs of the present-day and future climates by conducting many ANUC simulations.This Fellowship will shape a better understanding of the dynamics between cities and the atmosphere under HWs and will assess the effectiveness of mitigation strategies of cities under present-day and future climates, which will help building up HW resilient cities of the future.