Spatial-temporal pattern and multifactor driving mechanism of the heat island effect in the main urban area of Xi'an

Abstract

In the process of urbanization, the Urban Heat Island (UHI) effect has become a prominent issue affecting the urban ecological environment. Taking Xi’an’s main urban area as the study area, this work explores the spatiotemporal evolution and driving mechanisms of UHI to support climate improvement and ecological optimization. Specifically, using seven periods of Landsat images (2005-2021) and multi-source auxiliary data, land surface temperature (LST) was retrieved via the Radiative Transfer Equation (RTE), and UHI grades were classified by the mean-standard deviation method. Then, we analyzed UHI spatiotemporal patterns, intensity, and centroid migration at interannual and seasonal (2021) scales, and quantified driving factors with Geographical Detector and regression analysis. Constrained by Xi’an’s unique mountain-water-city topography, UHI shifted from a scattered multi-center pattern (2005) to concentrated zones in Weiyang, northern Baqiao, and the three central districts (Lianhu, Xincheng, Beilin) by 2021. In terms of seasonal variation, UHI was strongest in summer-autumn and weakest in winter-spring. Furthermore, the urban underlying surface dominated thermal changes: natural factors (elevation, Fractional Vegetation Coverage (FVC), Modified Normalized Difference Water Index (MNDWI)) correlated negatively with LST, with MNDWI (R²=0.557) and FVC (R²=0.443) showing significant cooling effects; anthropogenic factors (Normalized Difference Built-up Index (NDBI), population density, night-time light) correlated positively, with NDBI presenting the strongest warming effect (R²=0.547) and highest explanatory power (q=0.51, p<0.01). Overall, this study reveals UHI dynamics in Xi’an, supporting thermal environment planning for inland plain cities, and validates RTE for LST retrieval in topographically constrained inland cities.