Studying anthropogenic heat dispersion to improve urban climate resilience

The stagnated airflow around closely packed, tall buildings causes the weak removal of anthropogenic heat at urban areas. Therefore, it is crucial to investigate the effect of urban morphology on anthropogenic heat dispersion to make high density cities more resilient to future challenges such as, Urban Heat Islands (UHI), which causes long term stress and heat waves, which cause short term shock.

In this study, Prof. Yuan Chao, module leader of the Climate Resilience in High-Density Cities team at The Future Resilient Systems (FRS) programme and his co-authors developed a semi-empirical model to estimate spatially-averaged in-canopy air temperature increment based on the energy conservation within the urban canopy layer. Both site coverage ratio and frontal area density were identified as the key parameters of the exchange velocity and heat dispersion in street canyon parameters.

A Geographic Information System (GIS)-based modelling tool was developed to support decision-making in urban planning practice. The performance of the new model was validated by cross-comparing with Computational Fluid Dynamics (CFD) results from the parametric study, in which ten parametric cases with two heat emission scenarios were designed based on real urban areas.

By applying this new GIS-based model, the impact of urban morphology on anthropogenic heat dispersion was mapped at residential areas of Singapore. Both the annual average climate/emission scenario for long-term stress and the extreme scenario for short-term shock with low wind speed and high heat emission were evaluated.

Both steady and unsteady modelling results were provided. By using the new analytical model on transient urban street air warming, the researchers estimated the dynamic air temperature increment in residential areas with current heat emissions in 48 hours. The modelling results showed that it is difficult for anthropogenic heat to be dispersed in the short-term shock scenario. Also, air temperature could increase by 2 degrees, which is significant to both thermal comfort and public health.

The papers external page “Mitigating intensity of urban heat island by better understanding on urban morphology and anthropogenic heat dispersion” and “external page Analytical and Numerical Study on Transient Urban Street Air Warming Induced by Anthropogenic Heat Emission”  were published in Building and Environment and Energy and Building, respectively.