Numerical investigation of thermal patterns and local wind circulations to characterize Urban Heat Island during a heatwave in Turin

Heatwaves are annually increasing in terms of intensity and frequency. In urban areas, the impact could be further exacerbated by the Urban Heat Island (UHI) effect. This work carries out an urban microclimate numerical analysis to evaluate the behavior of the UHI in the city of Turin (Italy) during a heatwave event. Turin is located in the North-West region of Italy, boarded by the Alps mountain ranges in the west and hills in the East. The study utilizes the WRF/MLUCM model and considers the heatwave period in June 2019. The high-resolution urban land use/land cover data is generated from local climate zone (LCZ) generator tool provided by the World Urban Database and Access Portal Tools (WUDAPT) portal. The simulation is validated with the data provided by ARPA (Regional Environmental Protection Agency) meteorological stations located over the region. The lower root mean squared error of air temperature and higher index of the agreement show that the simulation is in good agreement with the observational data. The simulation results are then used to analyze the rural-urban temperature distributions over the diurnal cycle and local wind circulations. According to the simulated results, the city of Turin has higher near-surface UHI intensity during the night and early morning (with maximum intensity greater than 5 °C), whereas the intensity is diminishing during the mid-day hours. The simulated wind patterns show a significant reduction in wind intensity over the urban areas. This reveals the potential of creating wind ventilation inside the city to minimize UHI effect and enhance air quality. Ultimately, this research contributes valuable insights into addressing the challenges posed by heatwaves and urban heat islands in Turin and offers a foundation for the development of sustainable urban climate strategies.