Chapter 11 - Urban heat island effect in India: assessment, impacts, and mitigation

Abstract

Research for urban heat island (UHI) in India has accelerated in past few years covering not only megacities but small towns as well. This chapter presents a discussion on the UHI scenario in India, which is the second largest populated country and one of the top growing economies in the world. It examines UHI quantification across India from multiple assessment methods, possible impacts, mitigation strategies and finally, identifies future research directions. In India, UHI intensities up to 8–10°C have been reported in areas with dense urban and commercial pockets. The varied methods of determination of UHI (such as fixed instruments, mobile surveys, and satellite-derived measurements) at surface and canopy layer are discussed while noting the paucity of research for the boundary layer UHI in India. Measurements alone are not adequate due to limitations of instrumental installation and errors and spatiotemporal continuity. Hence, mathematical tools such as empirical models and numerical mesoscale weather prediction models are used to understand the UHI phenomenon at region of interest, assess major causative factors, and design mitigation strategies. Case studies of such model applications are presented in this chapter. UHI effect has shown significant implications on spatiotemporal rainfall patterns, perceived thermal comfort, and heat-related morbidity and mortality for Indian cities. The review brings out emergence of concepts such as regional heat island and UHI based on local climate zones. Efficacy of various mitigation measures such as increasing green cover/plantation, thermally resistant building materials, reflective coating, etc., on surfaces is discussed in detail. The comprehensive review of different aspects of UHI in this chapter should help the scientific community as well as the regulatory bodies to determine future research focus and action plans with regard to UHI effect, its impact and mitigation in India.