Quantitative comparison of seasonal and diurnal characteristics for urban heat using meteorological monitoring data

Investigating the seasonal and diurnal variation is essential for enhancing the understanding of urban heat islands (UHIs). However, the seasonally and diurnally continuous patterns of UHIs are not fully disclosed. To address this gap, we analyzed the temporal features of the T_air-based UHIs by using meteorological monitoring data in Xi’an, China. The maximum, minimum, average T_air and urban heat island intensity (UHII) were further quantified to elucidate the diurnally and seasonally continuous dynamics of UHIs in more detail. The results showed that the T_air variation in winter was analogous to the pattern in summer, with a small valley during 6:00–8:00 around sunrise and a peak during 15:00–17:00 before sunset. Meanwhile, the UHII in summer was generally higher than that in winter, accompanied by the diurnal UHII stronger than the nocturnal UHII. In terms of diurnal patterns in summer, the hourly UHII curve with a range from − 2.97 to 5.22 °C was significantly different from T_air. Furthermore, the nocturnal UHII were all higher than 2 °C, while the diurnal UHII were rarely above 2 °C. This indicated that high temperatures were not necessarily indicative of high UHIIs. The findings of this study offer valuable insights for deepening the understanding of the daily and seasonal variation for the T_air-based UHIs and provide a useful reference of urban heat resilience for urban planners and policymakers.