Integrated effects of land cover, topography, urban morphology, and PM2.5 on land surface temperature.

Rapid urbanization profoundly alters land surface characteristics, intensifying thermal stress and air pollution, yet the seasonal dynamics of land surface temperature (LST) in high-altitude cities remain poorly understood. This study focuses on Xining, a representative plateau city, to examine how land cover, topography, urban morphology, and atmospheric pollution jointly regulate urban thermal environments. We integrated multi-source remote sensing data into a multidimensional indicator system and applied XGBoost, SHAP, and structural equation modeling to quantify nonlinear contributions, threshold effects, and interaction pathways. The results reveal pronounced spatiotemporal heterogeneity, with the strongest urban heat island effects in summer and dominant topographic regulation in spring and winter. Seasonal shifts in leading drivers were evident: population density was most influential in summer, vegetation indices in autumn, and landscape fragmentation and terrain parameters in spring and winter. Nonlinear thresholds were identified, including enhanced cooling at moderate NDVI values and intensified warming once built-up intensity exceeded critical levels. Significant interaction effects, such as vegetation-impervious coupling in spring and terrain-albedo mediation in winter, further highlighted the complexity of urban thermal regulation. Collectively, these findings advance understanding of seasonally varying mechanisms in plateau cities and provide a scientific basis for climate-resilient urban planning in topographically complex regions.