Effects of urbanization on day-to-day temperature variability in China during 1961–2022

Short-term temperature fluctuations have significant impacts on public health, ecosystems, and economic development. This study analyzed the day-to-day temperature variability (DTD) based on the daily mean, maximum, and minimum temperatures across China from 1961 to 2022. The urban and rural stations were identified using high-resolution remote sensing land cover data, and the asymmetric responses of DTDMAX and DTDMIN to urbanization were revealed. The results showed that approximately 88 % of stations had positive ΔDTD values, suggesting greater fluctuations in the daytime than nighttime. In the Songliao and Haihe River basins, urban stations had higher annual mean ΔDTD (0.30 ± 0.02 °C) than rural stations (0.28 ± 0.03 °C), probably due to enhanced daytime heat storage and delayed nighttime heat release driven by rapid urbanization. By contrast, rural stations had higher temperature fluctuations (0.81 ± 0.03 °C and 0.66 ± 0.02 °C) than urban stations (0.40 ± 0.04 °C and 0.17 ± 0.02 °C) in the Southwest and Yangtze River basins, possibly due to the higher atmospheric moisture content in southern areas resulting in smaller daytime temperature variations. The ratios of DTD to the monthly standard deviation were between 0.2 and 0.9 for eight basins except Southeast River basin, indicating that the climate system was mainly characterized by orderliness. The impacts of urbanization were most pronounced in the Yellow River basin and Songliao river basin, where the ΔDTD values reached 0.28 °C/100a and 0.29 °C/100a, respectively. These findings can provide scientific insights for facilitating the formulation of region-specific climate adaptation strategies and for optimizing urban thermal management.