Seasonal hysteresis of surface urban heat islands

article Seasonal hysteresis of surface urban heat islands published yes Gabriele Manoli author Simone Fatichi author cf8e546b-a9b0-11f0-a43b-aa89ed1b56d6 Elie Bou-Zeid author Gabriel G. Katul author Temporal dynamics of urban warming have been extensivelystudied at the diurnal scale, but the impact of background cli-mate on the observed seasonality of surface urban heat islands(SUHIs) remains largely unexplored. On seasonal time scales, theintensity of urban–rural surface temperature differences (∆Ts)exhibits distinctive hysteretic cycles whose shape and loopingdirection vary across climatic zones. These observations high-light possible delays underlying the dynamics of the coupledurban–biosphere system. However, a general argument explain-ing the observed hysteretic patterns remains elusive. A coarse-grained model of SUHI coupled with a stochastic soil waterbalance is developed to demonstrate that the time lags betweenradiation forcing, air temperature, and rainfall generate a rate-dependent hysteresis, explaining the observed seasonal varia-tions of ∆Ts. If solar radiation is in phase with water availability,summer conditions cause strong SUHI intensities due to highrural evaporative cooling. Conversely, cities in seasonally dryregions where evapotranspiration is out of phase with radia-tion show a summertime oasis effect controlled by backgroundclimate and vegetation properties. These seasonal patterns ofwarming and cooling have signiﬁcant implications for heat mit-igation strategies as urban green spaces can reduce ∆Ts duringsummertime, while potentially negative effects of albedo man-agement during winter are mitigated by the seasonality of solarradiation. National Academy of Sciences2020 eng CitiesHysteresisSeasonalitySurface temperatureUrban heat island Proceedings of the National Academy of Sciences 0027-8424 1091-6490 32184330 10.1073/pnas.1917554117 117137082-7089 yes G. Manoli, S. Fatichi, E. Bou-Zeid, G.G. Katul, Proceedings of the National Academy of Sciences 117 (2020) 7082–7089. Manoli G, Fatichi S, Bou-Zeid E, Katul GG. 2020. Seasonal hysteresis of surface urban heat islands. Proceedings of the National Academy of Sciences. 117(13), 7082–7089. Manoli, G., Fatichi, S., Bou-Zeid, E., & Katul, G. G. (2020). Seasonal hysteresis of surface urban heat islands. Proceedings of the National Academy of Sciences. National Academy of Sciences. <a href="https://doi.org/10.1073/pnas.1917554117">https://doi.org/10.1073/pnas.1917554117</a> G. Manoli, S. Fatichi, E. Bou-Zeid, and G. G. Katul, “Seasonal hysteresis of surface urban heat islands,” Proceedings of the National Academy of Sciences, vol. 117, no. 13. National Academy of Sciences, pp. 7082–7089, 2020. Manoli G, Fatichi S, Bou-Zeid E, Katul GG. Seasonal hysteresis of surface urban heat islands. Proceedings of the National Academy of Sciences. 2020;117(13):7082-7089. doi:<a href="https://doi.org/10.1073/pnas.1917554117">10.1073/pnas.1917554117</a> Manoli, Gabriele, et al. “Seasonal Hysteresis of Surface Urban Heat Islands.” Proceedings of the National Academy of Sciences, vol. 117, no. 13, National Academy of Sciences, 2020, pp. 7082–89, doi:<a href="https://doi.org/10.1073/pnas.1917554117">10.1073/pnas.1917554117</a>. Manoli, Gabriele, Simone Fatichi, Elie Bou-Zeid, and Gabriel G. Katul. “Seasonal Hysteresis of Surface Urban Heat Islands.” Proceedings of the National Academy of Sciences. National Academy of Sciences, 2020. <a href="https://doi.org/10.1073/pnas.1917554117">https://doi.org/10.1073/pnas.1917554117</a>. 225422026-07-27T12:30:24Z2026-08-07T09:21:58Z