Characteristics of air temperature and thermal comfort in the grey and green spaces of an urban heat island

Urban green spaces are acknowledged as a vital component in a healthy city, providing a wealth of benefits. Urban green infrastructure (UGI) can help to moderate the intensity of the Urban heat Island (UHI), there is however a lack of high temporal and spatial ground-level data that quantifies the impact of UGI on air temperature and human comfort within UHI areas, and particularly for cities in temperate marine climates, which are not comprehensively understood. This paper therefore uses data from a high-resolution monitoring campaign in the UK city of Leeds to describe the diurnal characteristics of air temperature in grey and green spaces between May and August 2021. Average UHI intensity during this period was 0.9 °K, with a summer maximum of 3.1 °K occurring in late evening. Although there is variation across the monitoring sites, green space was on average 0.7 °K cooler than the grey spaces during the summer months, and up to 2.6 °K cooler on some of the hottest days. Air temperature in urban woods was up to 4.0 °K cooler on the hottest days. These measured data demonstrate the influence of UGI on air temperature in UHI areas, and quantify the impact of different types of UGI, identifying the UGI types that are most effective at regulating higher summertime air temperature. Results presented here provide valuable quantitative data that can support the protection and expansion of urban green space as part of policy development and urban planning in practice.