Three Decades of Urban Heat Dynamics in Patna, India: A Remote Sensing Based Hotspot Analysis

Abstract

Abstract: Rapid urbanization in tropical cities has intensified surface thermal stress, yet the long-term persistence and spatial structure of urban heat remain poorly understood, particularly in rapidly expanding cities of the Global South. This study investigates the three decades (1995–2025) of urban thermal dynamics in Patna, India, with a focus on identifying long-term temperature trends, examining their relationship with vegetation greenness and built-up expansion, and assessing the spatial persistence of urban heat hotspots. Using a longitudinal remote sensing framework, Land Surface Temperature (LST) was analyzed alongside the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI) derived from multi-decadal Landsat imagery processed in a cloud-based environment. A comprehensive spatiotemporal analytical approach integrating non-parametric trend analysis, correlation testing, hotspot persistence mapping, and multivariate regression modeling was employed to capture both temporal trajectories and spatial stability of urban warming. Results reveal a statistically significant increase in mean LST at a rate of approximately 0.13 °C yr⁻¹, accompanied by a strong and monotonic rise in built-up intensity, while vegetation greenness exhibits high interannual variability without a significant long-term trend. Spatial analysis identifies a marked regime shift around the mid-2000s, after which high-temperature zones persistently dominate more than 95% of the urban area, with no observed reversals over the subsequent two decades. Regression results confirm built-up expansion as the sole statistically significant predictor of long-term surface warming at the city scale. Collectively, the findings demonstrate that Patna has transitioned into a structurally persistent urban heat regime, driven primarily by sustained urbanization. The study provides robust empirical evidence of long-term urban heat persistence in a tropical megacity and offers a transferable analytical framework for identifying sustained thermal risk to support climate-sensitive urban planning and adaptation strategies.

Keywords: Land surface temperature (LST); Remote sensing; Vegetation dynamics; Urban heat persistence; Google Earth Engine (GEE); Patna