In the past century, local-scale warming caused by a strengthening urban heat island effect has brought inevitable systematic bias to observational data from surface weather stations located in or near urban areas. In this study, the land use situation around U.S. Climate Reference Network (USCRN) stations was used as a reference for rural station selection; stations with similar environmental conditions in the U.S. Historical Climatology Network (USHCN) were selected as reference stations using a machine learning method, and then the maximum surface air temperature (Tmax) series, minimum surface air temperature (Tmin) series and mean surface air temperature (Tmean) series of rural stations during 1921–2020 were compared with those for all nearby stations (including both rural and urban stations) to evaluate urbanization effects in the USHCN observation data series of the contiguous United States, which can be regarded as urbanization bias contained in the latest homogenized USHCN observation data. The results showed that the urbanization effect on the Tmean trend of USHCN stations is 0.002 °C dec−1, and the urbanization contribution is 35%, indicating that urbanization around USHCN stations has led to at least one-third of the overall warming recorded at USHCN stations over the last one hundred years. The urbanization effects on Tmax and Tmin trends of USHCN stations are −0.015 °C dec−1 and 0.013 °C dec−1, respectively, and the urbanization contribution for Tmin is 34%. These results have significance for understanding the systematic bias in USHCN temperature data, and they provide a reference for subsequent studies on data correction and climate change monitoring.

中文翻译：

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城市化对美国本土地表气温趋势估计的影响

近百年来，城市热岛效应增强导致局地气候变暖，给位于城市及其附近的地面气象站观测数据带来了不可避免的系统偏差。本研究以美国气候参考网络（USCRN）站点周边的土地利用情况作为农村站点选择的参考；采用机器学习方法选取美国历史气候网络（USHCN）中环境条件相似的站点作为参考站，然后得到最高地表气温（Tmax）系列、最低地表气温（Tmin）系列和平均地表气温将1921-2020年期间的（Tmean）系列农村站与所有附近站（包括农村站和城市站）进行比较，以评估美国本土USHCN观测数据系列中的城市化效应，这可以被视为城市化偏差包含在最新的均质 USHCN 观测数据中。结果表明，城市化对USHCN站Tmean趋势的影响为0.002℃dec−1，城市化贡献率为35%，表明USHCN站周围的城市化导致了至少三分之一的总体变暖。过去一百年来的 USHCN 电台。城市化对 USHCN 站 Tmax 和 Tmin 趋势的影响分别为 -0.015 °C dec−1 和 0.013 °C dec−1，城市化对 Tmin 的贡献为 34%。这些结果对于理解USHCN温度数据的系统偏差具有重要意义，为后续数据校正和气候变化监测研究提供参考。