Abstract
The combined effect of climate change and future urban growth will further increase air temperatures in cities, contributing more to what is known as urban overheating. A growing body of literature recognises the importance of nature-based solutions in providing resilience by mitigating urban heat islands. However, a knowledge gap exists regarding the contribution of blue spaces and how their behaviour varies depending on their geometry. This paper presents the main results of a novel study on the influence of urban blue space size and shape on in-canyon airflow and temperature/vapour distribution, and the associated implications on pollutant removal in a simplified urban neighbourhood. Using a numerical solver that accounts for evaporation effects, we examine the performance of isothermal waterbodies in a neutrally-stratified atmosphere under forced- and mixed-convection regimes and air-water temperature differences indicative of either daytime or night-time conditions. Results for forced convection show minimal impact on the flow structure, whilst temperature/vapour effects are distributed primarily over and around the water surface. Mixed-convection cases show that a cooler waterbody weakens the principal vortex in the open square, whilst temperature/vapour effects reach further upwind and are more widely distributed in the spanwise direction. An adequately sized warmer waterbody disrupts the skimming flow structure, indicating a possible heat and pollutant removal mechanism from around the waterbody and downwind canyons. Inadequately sized warmer waterbodies cannot promote sufficient vertical transport, leading to overturning and increased temperature and humidity levels at pedestrian level, thereby worsening environmental conditions and increasing the risk of heat-related illness and mortality. Hence, larger waterbodies are better suited to nocturnal transport of pollutants and accumulated warm air away from the urban surface, while smaller waterbodies are better suited to providing localised evaporative cooling. Lastly, irregular waterbodies may have a greater cooling effect across a larger area.
Original language | English |
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Publication status | Acceptance date - 3 Apr 2023 |
Event | 11th International Conference on Urban Climate - Sydney, Australia Duration: 28 Aug 2023 → 1 Sept 2023 Conference number: 11th http://www.icuc11.com |
Conference
Conference | 11th International Conference on Urban Climate |
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Abbreviated title | ICUC11 |
Country/Territory | Australia |
City | Sydney |
Period | 28/08/23 → 1/09/23 |
Internet address |