Abstracts

On the climatic synergies at the local, regional, and global scales. The impact on the built environment.

by Hassan Khan

Most cities across the globe are affected by urban overheating (UO), which is one of the most well-documented local-scale climate change phenomena. Extreme heat events have become more intense and severe in the twenty-first century, posing a substantial hazard to human health. Over the years, significant variations in global weather patterns have also been documented. The UO alters the land-atmospheric interactions and affects the regional and global climatic conditions. The synergies between such local, regional, and global climate changes, which may adversely affect health, economy, energy, and environmental quality, have never been examined and are a major concern in the context of global warming and rapid urbanization. Further, the combined impact of such climatic changes on the built environment has never been investigated and is also a pressing issue in the context of overheating and GHG emissions. The dissertation’s primary goal is to examine the interactions between local-scale UO, regional-scale heatwaves, and large-scale synoptic climatology and to assess how these affect the built environment. The association between UO, heatwaves, and large-scale weather patterns was investigated using the surface energy budget and innovative techniques, including the gridded weather typing classification (GWTC). The newly developed urban building energy models (UBEMs) were employed to investigate the combined impact of such climatic changes on the built environment. There had been reports of positive synergy between UO and heatwaves when the magnitude of UO increased dramatically. The key synergistic interactions between UO and heatwaves were the advective heat flux and land-coast distance, where the lack of coastal winds penetration during heatwaves kept the inland regions warmer by altering the available energy. The tropical maritime Tasman airmass (coming from north of the Tasman sea) and temperate maritime weather patterns were primarily responsible for humid-warm (HW) and humid conditions in the region during heatwaves. In addition to these moist unstable conditions, a significant impact of tropical continental airmass, arising over central Australia, was also documented during heatwaves, another thermal regulator between inland and coastal zones. A drastic increase in urban cooling energy needs and serious overheating issues in the built environment was also concluded under the combined impact of such climate changes, which was associated with the same dualistic large-scale weather systems. This research is the first of its kind, identifying the impact of microscale and mesoscale climate on the built environment and presenting the solutions to counteracting the global climatic change. The guidelines provided in the dissertation will aid in designing thermally resilient and heat-responsive cities.