Integrating albedo and remote sensing indices to assess the urban heat and greening priorities in Trincomalee, Sri Lanka

Abstract

Rapid urbanisation causes a dramatic increase in built-up areas, while natural vegetation is significantly diminished. Although this supports economic and social development, it has negative impacts on the environment and biodiversity. One of the challenges is the Urban Heat Island (UHI) effect, where built-up surfaces absorb and retain heat, raising urban temperatures compared to surrounding rural areas. The reduction of vegetation, expansion of impervious surfaces, and decline in surface reflectivity (albedo) collectively contribute to thermal stress and reduced urban livability. Assessing these interactions is crucial for climate-sensitive urban planning, especially in rapidly developing coastal cities such as Trincomalee, Sri Lanka. By analysing and correlating key remote sensing indices such as the Normalized Difference Vegetation Index (NDVI), Normalized Difference Built-up Index (NDBI), Normalized Difference Water Index (NDWI), Land Surface Temperature (LST), Urban Heat Island (UHI), Urban Thermal Field Variance Index (UTFVI), Greening Priority Index (GPI), and Albedo, this study aims to identify the spatio-temporal variations in green cover and heat patterns between 2015 and 2025 in Trincomalee Town and Gravets DS Division.