Correlation between Land surface temperature and spectral indices through assessment of UHI magnitude in Coimbatore, India

This study systematically examines the relationship between urbanization and Urban Heat Island (UHI) intensity through an analysis of Land Use Land Cover (LULC) changes, Land Surface Temperature (LST) trends, and spectral indices (Normalized Difference Vegetation Index (NDVI), Normalized Difference Built-up Index (NDBI), and Normalized Difference Moisture Index (NDMI)) over 28 years from 1994 to 2022. This study is needed due to the growing evidence that urban expansion worsens UHI effects, which impact environmental sustainability and urban resilience. In recent decades, urbanization in Tier-2 cities in India has intensified the UHI effect.

The results reveal an increase of 92.7 km² in built-up areas, alongside a decline of 36.7% in vegetation cover. Over the study period, LST rose from 29.18°C in 1994 to 40.42°C in 2022, indicating an annual average temperature increase of 0.28°C. The spectral indices reinforce these findings, illustrating decreasing vegetation (NDVI), expanding urban surfaces (NDBI), and reduced moisture levels (NDMI), which significantly correlate with the intensification of UHI effects.