Quantifying the cooling effect of urban green space: A case from urban parks in a tropical mega metropolitan area (India)

Green space (GS) plays a crucial role in reducing the urban heat island (UHI) effect and helps in mitigating climate change. In Indian cities, GS are highly vulnerable due to rapid urbanization and infrastructural development. This study aims to assess the cooling effect of urban parks such as GS on the thermal environment in Kolkata Metropolitan Area (KMA), India. Five urban parks were selected from different parts of KMA for the assessment during the summer season. Three greenness indices (normalized difference vegetation index, enhanced vegetation index and soil adjusted vegetation index) and two thermal indices (land surface temperature and temperature condition index) were used to find out the cooling effect on the thermal environment. Relative land surface temperature (RLST) and vegetation cooling index (VCI) was developed for a better understanding of the relationship between greenness on the thermal environment. Correlation and regression analysis was also performed to show the relationship as well the effect of greenness parameters on thermal conditions. From the result, it was found that urban parks had a substantial impact on the cooling effect. (i) Botanical Park was the coldest park with an average LST of 33.55⁰C, followed by Nicco park (34.33⁰C), Nature park (34.48⁰C), Rabindra Sarabor (34.55⁰C), and Central Park (36.65⁰C) (ii) RLST had a negative correlation with PV (R = -0.51 for Botanical Park; R= -0.65 for Nature park; R= -0.57 for Central park) and (iii) finally, greenness had a negative impact on the thermal pattern in KMA (R = -0.16). Thus, from the results, it was documented that urban parks (as GS) had cooling effect on the surrounding areas. Therefore, the conservation of GS is essential to achieving sustainable development goals (particularly goals- 3, 11, 13, and 15).