Cooling Effects in Large Urban Mountains: A Case Study of Chengdu Longquan Mountains Urban Forest Park

Large Urban Mountains (LUM) with their rich vegetation cover offer a key natural solution to mitigate Urban Heat Island (UHI) effects. This study uses Longquan Mountain Forest Park (LMFP) as a case to investigate the spatiotemporal variations in cooling effects and the key factors influencing cooling intensity. Using Landsat images from 2001, 2011, and 2023, surface temperatures (LST) were retrieved through radiative transfer methods, and the thermal environment and cooling effects of LMFP were systematically analyzed. The eXtreme Gradient Boosting (XGBoost) model and Shapley Additive exPlanations(SHAP) methods were applied to explore the complex relationships between cooling intensity and its driving factors. Results show that in the years 2001, 2011, and 2023, the heat island area in LMFP has gradually shrunk, while the cooling intensity area has expanded. In the three years, the cooling distance increased from 330 m to 420 m, the cooling area expanded to 124.84 km2, and cooling efficiency increased to 18.31%. Vegetation coverage, leaf area index (LAI), and elevation are core factors influencing cooling, while human activities such as population and road density have a negative impact. This study provides important theoretical insights into the cooling mechanisms of large urban mountain parks.