Spatiotemporal analysis of air flow and ecosystem function under changing heights and density of urban buildings and climate

Urbanization and environmental changes increase the heights and density of urban buildings, city patterns and landscape, and city road networks. This could change urban wind flow and distribution, and air circulation, leading to air pollution, and other environmental risks, such as heat island. Therefore, it is necessary to improve our understanding of how urbanization and climate change influence spatiotemporal changes of wind and air quality. This study aims to evaluate spatiotemporal changes of wind speed and distribution in urban regions and identify the main factors affecting urban air flow and circulation due to horizontal and vertical urban development and the climate change impacts in three municipal zones in Tehran, using remote sensing, high-resolution photogrammetric images, and ENVI-MET software. The three-dimensional air flow was simulated using the SSP 2.4.5 climate change model and ENVI-MET software. The results showed that the relative share of buildings reaches 47.3% of the total space with 31.4% in zone 1 and 40.6% in zone 2, and 60.7% in zone 3. Building density and building height are two of the main factors that represent 76% and 62% inhibitory effects on intra-urban flow, respectively. The heights of buildings significantly influence the local wind direction but do not change the direction of the wind in regions. In contrast, the building density could change positively the regional wind directions by 52% on the ranges above 300 units per hectare. It is predicted that the average wind flow will decrease from 2.57 in 2020 to 1.44 m/s in 2050 due to climate change. This demonstrates that city topography and buildings do play a significant role in changing the direction and speed of the wind. The results of this study are therefore useful for designing new buildings and urban planning for mitigating air quality in tropical cities.