Building Resilient Cities for Heat Waves

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.

This fellowship will shape a better understanding of the dynamics between cities and the atmosphere under HWs and will assess the effectiveness of different heat mitigation strategies of cities under present-day and future climates, which will lead to HW resilient cities by reducing thermal stress.

The non-academic beneficiaries of this Fellowship include climate service sectors and school children.

1) Climate Service Sectors
Climate service sectors will benefit from the Analytical Urban Climate (ANUC) framework, a state-of-the-art urban climate toolkit developed in this Fellowship, by providing modelling needs and conducting climate service driven simulations. Users in these sectors include infrastructure providers, human health sectors, logistics organisations, etc. The ANUC framework is designed as an agile simulation tool so that the climate service sectors can more rapidly get informed with possible impacts of various infrastructure designs and synoptic processes on urban climate.

2) School Children
Young people are interested and concerned about the environment and climate change and it is they who are the future policy makers, scientists, engineers, etc. Given this, I propose to develop some online resources, based on the ANUC framework, to increase awareness of climate change and enhance understanding of climate science. By presenting not only the simulations and impacts of HWs on urban climate and the effectiveness of heat mitigation measures by designing and performing ANUC simulations, the underlying analytical framework will also be explained to show the importance and application of mathematics to real-world environmental issues and understanding. These resources will be appropriate for use by teachers in classrooms or interested students (KS3 level and above). Delivery of both elements will involve an interactive website to demonstrate the impacts of HWs on urban climate and the effectiveness of different heat mitigation measures under HWs in various climates. The website will be driven by the ANUC framework in the Wolfram Cloud, which will enable it to be interactive and to be able to use global climate forcing data. Interactive functions will be implemented to allow the users to design and perform simulations in their cities and other areas of interest over the world under both present-day and future climates.