Remote sensing analysis of urban heat island effect in Colombo city from 2001-2019

Abstract

Urban Heat Island (UHI) is a metropolitan area where the temperature is several degrees higher than surrounding rural areas. In the context of UHI phenomenon, Land Surface Temperature (LST) was estimated using Landsat satellite images covering Colombo city, which is one of the main commercial metropolitan cities in South Asia. Results revealed that UHIs have expanded into northern, eastern and south eastern regions of Colombo city within the period 2001-2019. The Land Use change indicated the rapid urbanization. The correlation of Normalized Difference Built up Index (NDBI) and Normalized Difference Vegetation Index (NDVI) with LST were analyzed and obtained negative correlation between NDVI & LST and positive correlation between NDBI & LST at four time period (2001,2009,2016 & 2019) indicating the vegetation can weaker the UHIs while built up land can strengthen the UHIs. The results of Albedo analysis show that the low albedo materials have more potential influence towards formation of UHI. Finally, according to the ecological evaluation of the city using Urban Thermal Field Variance Index (UTFVI), 27% of the area is experienced worst case of heat stresses remaindering that mitigation measures should be applied in future urban planning to uplift the quality of lives and environment.