Using historical meteorological data from the Societa Meteorologica Italiana and Arpa, an analysis was performed to identify the most significant heat wave events since the late 1980’s. These dates were evaluated against available satellite imagery from multiple sources, in order to identify events where complete data was available for analysis of surface temperature in Torino.
Available imagery for Torino was reviewed from both the ASTER and Landsat satellites. Considering the dates of the extreme events, data was retrieved for both 21 July 2006 and 22 July 2015. Other dates had only partial coverage of the city or significant cloud cover, which would interfere with the analysis.
In order to define the hazard level for different temperature ranges resulting from the UHI analysis, the variability of the data was assessed based on standard deviation from the mean. Areas more than one standard deviation below the mean temperature (for the extreme events considered) were considered to have no hazard threat. The thresholds for the other hazard levels are defined below:
- Low hazard: temperature within one standard deviation of the mean (26.5 % of the total Municipality’s surface)
- Moderate hazard: temperature between one and two standard deviations above the mean (43.6 % of the total Municipality’s surface)
- High hazard: temperature greater than two standard deviations above the mean (2.1 % of the total Municipality’s surface)
The high hazard areas are concentrated around two main clusters of industrial buildings: around the Fiat complex to the southwest, and near the IVECO complex to the northeast. Much of the developed areas of the city are within the moderate hazard area, including a majority of the six industrial areas studied in the DERRIS project.
According with the needs of the Municipality, an exposure analysis was developed in order to identify the population exposed and the infrastructures. Each system was spatially overlaid
with the UHI map in the GIS to determine where and to what degree each system is exposed. Exposure maps were generated in order to help guide development decisions in the future.
As shown above, almost the entire population of the city is exposed to the UHI, in fact in the area not exposed to the risk there is no residential population. The entire analysis and the results obtained were validated during the first workshop developed on June 21th.