Quantifying the impact of urban green space pattern on urban mesoscale thermal environments: a modeling perspective

Abstract

Green space is an important adaptation strategy for alleviating urban thermal environments. However, the spatiotemporal changes of urban green space and their impact on urban mesoscale thermal environments remain understudied. This study first incorporated the gridded green fraction of central Wuhan in 2016 and 2020 into a mesoscale model coupled with an urban canopy model to quantify the impact of changes in green space on urban thermal environments. Then, we used constraint line method to analyze the relationship between morphological spatial pattern of green space and land surface temperature. Results showed that the green space in central Wuhan changed considerably with an overall increase of 13.37 km2. Generally, a 10% increase in green fraction could produce a nighttime cooling of 0.167℃ but a daytime cooling of 0.075℃. In contrast, it could give rise to an increase in near-surface humidity by 0.131 g/kg in the daytime and by 0.042 g/kg in the nighttime. As a result, green fraction had a stronger and more positive impact on nighttime thermal comfort. For the morphological spatial patterns of green space, we found that the difference in land surface temperature between the islet and the core was 4.3K. Increasing branch fraction have greatest decreased magnitude of land surface temperature. Increasing green space is an effective approach to alleviate urban thermal environment. Addition of greenery around existing greenspace (to increase the edge area) and enhancing their coherence (increasing bridge and loop) are more effective than modifying size or shape of existing.