Detailed intra-urban thermal monitoring in Florence and application of biometeorological indices: the effect of green areas

Thermal comfort is a topic of particular interest for experts, such as urban planners, architects, biometeorologists and physicians, dealing with quality of life of people living in urban areas. It is well known that thermal comfort is influenced by urban design at the micro-scale and features like the presence of parks and street canyon can influence micrometeorological variables that control the human thermal sensation. This study deals with urban human-biometeorology on the micro-scale, and its main purpose is to quantify the intraurban thermal comfort variability of the city of Florence and investigate the influence of green area. Steadman heat Index, Humidex and Thom Discomfort Index were calculated from meteorological variables collected by 15 sensors distributed in Florence urban area during summer 2010. Seasonal and hourly average were analysed and compared with the percentage of green areas nearby the sensors. The average number of discomfort hours in Florence was approximately 891 hours for Steadman heat Index, 1485 hours for Humidex and 1605 hours for Thom Discomfort Index, with a maximum discomfort difference between the hottest and the coolest station of respectively 541, 464 and 402 hours. Discomfort variability was significantly correlated with the percentage of green areas surrounding the sensor and a 10% increase of green area determine approximately a reduction of 30 hours of discomfort according to all indices. All these results show that citizens living in the same city may be subjected to different level of discomfort according to the local urban characteristics of the place where they live and underline the importance of future studies that can provide tools to assess the impact of urbanisation on quality of life and health.