Evolution of urban morphological polycentricity and the thermal response in Wuhan from 2000 to 2020

The emergence of urban polycentric development patterns in response to the pressure of rapid urbanization can profoundly affect the urban heat island (UHI) effect. However, little research has been conducted on this issue at a high spatio-temporal resolution level. To investigate the evolution of urban polycentricity and the accompanying changes in the urban thermal environment, data for 2000 to 2020 from Wuhan in China obtained by multiple sensors were used to extract the urban morphological centers each year and generate annual summer mean land surface temperature (LST) with a 30 m resolution. Results show that the number and size of urban morphological centers in Wuhan increased significantly, from five centers covering 29.75 km² in 2000 to 15 centers covering 171.72 km² in 2020. The annual average growth rate was rapid (0.152 km²/a) from 2000 to 2012, then slowed down (0.026 km²/a). The location of newly emerged urban centers aligned with Wuhan's urban development planning. Meanwhile, the urban thermal environment also changed considerably. The summer mean LST have risen by around 1 K, whereas the area of high LST centers fluctuated in the recent two decades. The evolution of urban morphological centers and high LST centers was not always synchronized, with changes in the former showed hysteresis behind the latter, and overlapping areas between the two reaching the maximum at an interval of about nine years. These findings will further our understanding of the urban polycentricity, as well as the evolution of the urban thermal environment in this context.