Music-Cultural Nighttime Vitality–Heat Relationships in Urban Systems: Temporal Asymmetry and Spatial Scale Dependence

Urban nighttime vitality and daytime surface heat are often examined separately, leaving unclear how their relationship varies across spatial supports and stages of urban change. This study examines music-cultural nighttime vitality across 4593 fixed 500 m grids in Changsha, China, from 2013 to 2024. We integrated a 2025 music-cultural point-of-interest inventory, annual VIIRS nighttime radiance, warm-season Landsat land surface temperature, and built-environment data. The 2025 music-cultural representativeness index served as a fixed present-day functional reference, while annual radiance captured temporal variation in nighttime activity. Same-grid and neighborhood analyses were used to evaluate spatial scale dependence, and stage-specific relative-change analysis assessed temporal asymmetry. High-MCNVI grids consistently showed greater high-heat prevalence than low-MCNVI grids, with same-grid overlap exceeding spatially constrained null expectations. Bivariate LISA identified recurring high-vitality–high-neighboring-heat clusters, while site and neighborhood thermal levels remained closely aligned. Under the primary 2018 stage division, the dominant relative-change regime reversed from negative-decoupling dominance in 2013–2018 to decoupling dominance in 2018–2024, with the directional contrast shifting from −47.95 to 55.63 percentage points. Panel and XGBoost–SHAP analyses further showed that vegetation and built-up intensity were more consistently associated with DSHBI and contributed more to prediction than function-specific nighttime vitality. These results distinguish spatial scale dependence from temporal asymmetry and provide a function-specific framework for examining the thermal context of urban nighttime culture.