Urban climate and local climate zone classification in the city of Kochi in India

Rapid growth in urbanization significantly alters the natural environments and lead to distinct urban climates. This development leads to Urban Heat Island Effect (UHI), the phenomenon of elevate temperature within the urban area with respect to adjoining rural areas. Urban geometry is one of the most important factors that cause urban-rural and intra-urban air temperature differences. The formation of UHI is thus exacerbated due to the complex heat exchange between buildings and surrounding. Local Climate Zone classification (LCZ) put forward by Stewart and Oke distinguish each LCZ zones based on the building and surface morphology. So this approach gives a better understanding on UHI based on properties of urban materials and surfaces rather than meteorological parameters. Hence this study has investigated the variation of UHI intensity in different local climate zones in Kochi, a tropical coastal city in India. Kochi in Ernakulum district is one of the fast growing cities in the south west coast of India. Mobile surveys were conducted within the city and adjacent rural areas during winter and summer seasons, covering pre-dawn and early evening periods in 2019. The correlation between UHI intensity and Local Climate Zone classification was analysed. The Urban Heat Island intensity and spatial temperature distribution exhibits a good correlation with the Local Climate Zone Classification. Highest observed urban heat island intensity in Kochi was 5.3 °C and 4.3 °C during winter and summer morning respectively. Maximum observed UHI intensity in both seasons during late evening was 3.3 °C. Central part of the city which falls under Compact midrise zone exhibited maximum UHI intensity and reference station comes under sparsely built zone indicated minimum intensity during the mobile surveys. Proper planning of the built environment and selection of raw materials is necessary to reduce the problem of excessive nocturnal heat within the built environment. Conservation of wetlands is the easiest and appropriate method to reduce the heat island effect in the study areas.