Analyzing the Spatial-Temporal Patterns of Urban Heat Islands in Nanjing: The Role of Urbanization and Different Land Uses

This study explores the spatiotemporal distribution and formation mechanisms of urban heat islands (UHIs) in Nanjing during summer, utilizing temperature data from 82 automatic weather stations (AWSs) distributed across five concentric zones. The results demonstrate the substantial impact of urbanization on UHI patterns, with industrial and densely populated areas exhibiting higher UHI intensity (UHII), while regions with natural landscapes such as mountains and water bodies display lower temperatures. The analysis reveals that the most pronounced night-time UHI effect occurs in the highly urbanized central zones, whereas the weakest effect is observed during midday. Transitional UHI phases are identified around sunrise and sunset, with increased long-wave radiation post-sunset amplifying the UHI effect. Additionally, this study underscores the directional characteristics of UHI distribution in Nanjing. Notably, Hexi New Town has emerged as a new high-temperature hotspot due to rapid urbanization, while Jiangning New Town and Xianlin Sub-City maintain lower temperatures owing to their proximity to agricultural and forested areas. By selecting representative AWSs from different zones, this study introduces a novel and practical method for calculating UHII. Although the approach has limitations in precision, it provides an accessible tool for UHI analysis and can be adapted for use in other cities. This research offers valuable insights into the influence of urban development on local climate and presents a practical framework for future UHI studies and urban planning strategies aimed at mitigating UHI effects.