Quantitative analysis of passive cooling measures in achieving a thermally comfortable urban environment

Abstract

The advancement in technology and rapid globalization have resulted in the emergence of metropolitan cities and agglomerations that are constantly expanding to meet the ever-growing demand of migrating populations. With climate change being an inevitable reality, rampant urbanization has exacerbated impacts such as extreme weather events and the development of urban heat islands. Several researchers and the scientific community have proposed mitigation strategies based on the spatio-temporal changes in Land Use/Land Cover (LU/LC) and Land Surface Temperatures(LST). The studies, however, have not yet established the definite effect of using proposed mitigation strategies on land surface temperature reduction for different urban landscapes. Henceforth, this research aims at quantifying the effect of several mitigation strategies on land surface temperatures, and the analysis was performed over Kolkata city (area under Kolkata municipal corporation). The study focused on developing scenario-based analysis to capture the effectiveness of the interventions required with changing urban density, location and built morphology. The land use and land surface temperature maps developed in the course of the investigation indicated that the impervious urban surfaces correspond to the highest surface temperatures across the study area. In conjunction with the normalized urban heat island (NUHI) index and LST results, the land surface temperature map for Kolkata city was divided into five heat zones. The five priority areas for quantifying the impact of mitigation strategies on LST reduction were chosen from heat zones 4 and 5 (depicting high and very high LST categories as per the global standards). The mitigation scenarios comprising surface greening and changes in building material were applied to the selected areas with varying urban morphologies. The research analysis performed denoted the effect of individual and combined mitigation scenarios based on the efficiency of strategy to bring an optimum cooling effect. It was observed that the cool strategy resulted in the highest temperature difference for both neighbourhood and building levels, whereas the combination scenario corresponded to the highest decline in surface temperatures across the neighbourhood level