Spatio Temporal Assessment of Urban Heat Island Dynamics Using Geospatial Techniques: A Case Study of Kozhikode, Kerala, India

Abstract

Across India, medium-sized towns frequently experience unplanned urban growth and the ensuing environmental problems. In addition to notable reductions in water bodies and vegetation cover, unchecked, rapid urbanisation has led to a marked expansion of built-up areas. Such transformations of once-green urban landscapes have intensified environmental risks and exacerbated climate-related issues. Geospatial technology is a powerful tool for quantifying land-cover transformations and the resulting temperature increase. The present study investigates the spatio-temporal dynamics of urban temperature rise and its association with accelerated urban growth and resultant land-use/land-cover (LULC) transformations in the Kozhikode city region, from 1993 to 2023. To quantify these LULC changes, a combination of remote sensing and Geographic Information System (GIS)-based analytical techniques (Various spectral indices (NDMI, NDII, GNDVI, NDbaI) and Land surface temperature) was employed. The study reveals a pronounced intensification of built-up land and a corresponding depletion of vegetation cover. The mean GNDVI value decreased from 0.53 in 1993 to 0.51 in 2023. Similarly, the moisture index showed a declining trend. It transformed from 0.27 in 1993 to 0.23 in 2023. Conversely the bareness index and impervious index showed a marked acceleration over the research period. It transformed into -0.43 in 1993 to -0.17 in 2023 and -0.43 in 1993 to -0.17 in 2023 respectively. The steadily increasing land-surface temperature readings during the research period provide further evidence of accelerating urban warming in the study area. The mean Land Surface Temperature value accelerated into 35.59°C in 2023 from 29.24°C in 1993. The spatial analysis of Land Surface Temperature (LST) reveals that elevated temperature zones are predominantly concentrated in intensively built-up areas, particularly within the 5 km buffer surrounding the city core. The findings clearly indicate that regions characterised by higher built-up density function as urban heat island (UHI) zones within the city.