Characterization of the UHI in Zaragoza (Spain) using a quality-controlled hourly sensor-based urban climate network

The study of the urban heat island (UHI) is of great importance in the context of climate change, where increasingly frequent and intense extreme thermal events will generate lethal effects in cities. In this work, we characterize the UHI of the urban area of Zaragoza (Spain) using a thermohygrometric network of hourly observatories composed of 21 sensors, from March 2015 to February 2021. Due to the diversity of urban spaces and the high volume of information (≈ 995,000 observations), we performed an exhaustive quality control. Incorporating a synoptic analysis to better identify atmospheric situations not recorded by sensors. The results indicate that 1.6% of observations are removed, mainly due to outliers and hourly variability. We demonstrate that the UHI displays the classical center-periphery pattern with intensity values around 2 °C, but with variations due to the urban structure. We also observe seasonal UHI variations that intensify, especially in winter and autumn nights. Finally, this characterization confirms the differences in UHI intensity are due to their structural and climatic characteristics, which can ultimately guide the logical urban planning design of Zaragoza, and other Mediterranean-like cities with a similar urban environment. •Extensive sensor network identifies UHI climatic patterns in different urban areas.•Nocturnal UHI intensity exceeds 2 °C on average in central urban areas of Zaragoza.•UHI intensity is higher during winter and autumn nights, exceeding 4 °C.•In the morning, UCI is seen in the city center with intensities around 0 °C or lower.•Using situations in QC shows atmospheric events not included in climatic databases.