Assessing nature-based solutions and blue infrastructure for outdoor thermal comfort in a Mediterranean city (Lecce, Italy)

The aim of this study is to evaluate the effectiveness of nature-based adaptation measures and blue infrastructure for thermal comfort in an area of ​​Lecce (Southern Italy), a typical Mediterranean city. Although numerous similar studies have been conducted worldwide, the literature presents a gap in knowledge regarding Italian Mediterranean cities, where the effects of intense heat are more evident, especially in summer.

The study area is a small square in the city center, currently undergoing a redevelopment project approved by the Municipality of Lecce.

The methodology involves the use of ENVI-met, a microclimate simulation software. The meteorological inputs used come from ERA5 reanalysis data for the period 1991-2020 and from climate projections of RCP (Representative Concentration Pathways) 4.5 and 8.5 for the mid-term (2041-2060) and long-term (2081-2100). Three scenarios are simulated: one current and two modified according to the redevelopment plan, one including increased vegetation and permeable surfaces and the other including the addition of a fountain. They are simulated on a typical summer day in the current period and in future scenarios of RCP_4.5 and RCP_8.5 over the medium and long term.

Preliminary results, provided in terms of the Physiological Equivalent Temperature (PET) index, show a reduction in ‘strong heat stress’ for modified scenarios compared to the current scenario, but an increase in ‘extreme heat stress’ for the scenario with a fountain due to higher relative humidity. This is more evident under current climate conditions rather than the most unfavorable long-term climate projections.

The approach proposed in this study represents a valuable decision-making tool for researchers, policy-makers, and urban planners, allowing them to evaluate the effects of various climate adaptation strategies by estimating thermal comfort and adapting this methodology both for Mediterranean cities and, more generally, for any urban environment.