Due to differences in energy balance, urban areas typically experience greater temperatures than surrounding rural areas, a phenomenon known as the urban heat island (UHI) effect. This urban–rural temperature difference can vary greatly, and the magnitude of the UHI depends on the time of day, season, and weather conditions. This study used 12 years of observational records from an extensive sensor network in Madison, Wisconsin, to explore patterns in short- and long-term variability of the local UHI, as well as the meteorological drivers of this variability. We identified a statistically significant year-round inverse correlation between wind speed and UHI magnitude. For other meteorological variables, correlation with the UHI varied seasonally, with the strongest dependence on temperature occurring during the winter and the strongest dependence on precipitation occurring during summer and fall. We also observed a greater frequency of inverted heat islands – days when urban temperatures dropped below rural temperatures – than previously documented in Madison or climatically similar cities. Additionally, we identified marked differences between spring and fall conditions that point to the role of prior seasons in shaping the UHI. Overall, the trends documented here have the potential to inform the development and evaluation of heat mitigation efforts in the Madison area. More broadly, the degree of variability observed in this study relative to prior analyses highlights the benefits that long-term, year-round monitoring can provide to urban climate planning throughout the world.
Berg et al. (Sun,) studied this question.