Analysis of the influence of ground cover and shade on daily temperature variation: a case study in Florence (Italy)

As more than half of the world population live in cities, the design of liveable urban spaces is increasing- ly a strategic issue. Therefore, urban planners need tools allowing the evaluation of the benefits of de- sign choices that take into account thermal comfort. Ground surface characteristics as well as shading conditions can affect spatial temperature variability of an urban area. The aim of this study was to inves- tigate the relationship between different types of urban ground covers, sun exposure conditions and daily variation of air temperature. Our case study was based on data collected in two sites of the urban area of Florence in summer 2013. For each site, five weather stations equipped with air temperature, rel- a t i v e h u m i d i t y a n d s o l a r r a d i a t i o n s e n s o r s w e r e s e t u p a t 2 m e t e r s h e i g h t t o a n a l y s e t h e t h e r m a l c o n d i- tions at pedestrian level. Each station was classified according to ground cover characteristics (permeability and albedo), use of irrigation in green areas and sun exposure. The relationship between these characteristics and hourly variation of air temperature was investigated. According to our results shading conditions explained more than 70% of temperature variability during the hottest hours of the day. Air temperature over the shaded green surface was 3°C lower than temperature over sandstone ex- posed to the sun. On the other hand, night temperatures were significantly reduced by approximately 1° C on permeable surfaces