The urban heat island effect in a small Mediterranean city of high summer temperatures and cooling energy demands

• Urban heat island (UHI) is present even in small-sized towns like Agrinio.
• Mean hourly UHI intensities up to 6 °C were determined.
• Significant correlation of UHI intensity and city ventilation was observed.
• 36.3% higher cooling energy needs in the city centre compared to rural.
• High increase of cooling energy needs in a future climate change scenario.

The results of an urban heat island (UHI) study during summer and winter through a full year period (2010–2011) in a small city of western Greece are presented and analyzed. The specific research target was to identify the existence of the phenomenon, measure its intensity and investigate the parameters that may be associated with the appearance of the UHI. A network of air temperature sensors was installed in nine different locations of the city and measurements were recorded every 10 min. Extensive statistical analysis revealed strong UHI intensities reaching values up to 6.0 °C with a mean intensity of 3.8 °C during nocturnal hours of August. Heat island in the city proved to be a night dominating phenomenon while wind velocity was found to wield great impact on the ventilation and cooling effect of the city. During summer, early in the morning many locations in the city centre remained cooler than the rural environment while a heat island was observed on a monthly basis during winter. In order to determine the variation of the current energy needs due to the UHI effect, the heating degree hours during winter were calculated and were found to be much lower in the city centre than in the rural area (12.6–14.2% reduction). During summer, a high increase in the cooling degree hours of the city was observed in comparison to the rural environment, with a maximum difference of 36.3% for August 2010.

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