Assessment of urban thermal field variance index and defining the relationship between land cover and surface temperature in Chattogram city: A remote sensing and statistical approach

Land Cover (LC) is going through a dramatic change due to rapid urbanization, especially in urban areas. The impervious land covers (built-up areas) are replacing the natural land covers (vegetation and waterbody) rapidly, which significantly contributes to the increase of Land Surface Temperature (LST). Increased LST deteriorates the meteorological condition in urban areas and causes Surface Urban Heat Island (SUHI) effect. The vulnerability of the SUHI effect can be described quantitatively and qualitatively by Urban Thermal Field Variance Index (UTFVI) phenomenon. The study investigates the changing pattern of the SUHI and its magnitude with Landsat TM/OLI time-series satellite imageries from 1988 to 2018 and establishes the relationship between LC change and LST variations in Chattogram city. The relationships are defined by correlation analysis, cross-section profiles, and Simple Linear Regression Models (SLRM). The results suggest that vegetation cover, water body, and bare-soil have decreased by 2%, 7%, and 10%, respectively, where the built-up area has increased by 19% in the study area during the study period. The average LST of the study area has increased by approximately 10 °C in the last 30 years. Weightage of the SUHI affected area has also increased over time due to its direct linkage with LST. No area was affected by the SUHI phenomenon in 1988, which was found more than 35% in 2018. Only 1.69% area was found under the strongest UTFVI phenomenon in 1988, which increased significantly by 27.53% in 2018. In statistical analysis, regression models are used to define LC and LST relationship for every LC type. The LC and LST relationship analyses demonstrate a significant positive correlation with the built-up area while it is negative with vegetation, waterbody, and bare soil. The findings of this study will help city officials and policymakers to prepare a sustainable urban land development plan to minimize the negative consequences of unplanned urbanization and heat stress-related issues.