Spatio-temporal Evolution Characteristics and Interrelationships between Land Surface Temperatures and Air Pollutants in Chinese Cities

Urbanization in China has profoundly altered the urban thermal environment and air quality, imposing significant pressures on urban ecosystems. While the urban heat island (UHI) effect and air pollution are often studied in parallel, their spatio-temporal interrelationships remain complex and not fully quantified across different scales. This study investigates the coupling between land surface temperature (LST) – a key driver of UHI – and major air pollutants (PM2.5, PM10, O3) across Chinese cities from 2003 to 2024. We employ a suite of advanced analytical methods, including spatial correlation analysis to characterize the spatial dependence of LST within urban agglomerations, and trajectory modeling to identify key pollution-affected regions and dispersion pathways. Methodologically, the core innovation lies in integrating Continuous Wavelet Transform (CWT), Seasonal-Trend decomposition using Loess (STL), and Multifractal Detrended Cross-Correlation Analysis (MF-DCCA). This integrated framework enables a novel multi-scale analysis that captures both the time-frequency dynamics and seasonal characteristics inherent in the LST-pollutant relationship. Our results reveal distinct scale-dependent associations: The relationship between PM2.5 and LST is relatively straightforward at larger scales, whereas the linkage between O3 and LST exhibits the greatest complexity across scales. Conversely, PM10 shows a clearer association with LST at smaller scales. Notably, the strength of cross-correlations for all three pollutants diminishes at larger scales. The multiscale approach advanced in this study successfully quantifies the multi-faceted interplay between LST and pollutants, effectively overcoming the limitations of conventional spatio-temporal analyses. It establishes a new paradigm for elucidating nonlinear relationships in complex environmental systems and provides an efficient methodology for deepening our understanding of the coupling mechanisms between air pollution and the urban thermal environment.