呼和浩特市主城区夏季地表城市热岛强度昼夜差异及其统计关联

Day-Night Differences and Statistical Associations of Summer Surface Urban Heat Island Intensity in the Main Urban Area of Hohhot, China

摘要: 以呼和浩特市主城区为研究对象，基于2013~2023年夏季TRIMS LST数据，结合GUB动态边界、GAIA建成区数据、MNDWI及ERA5-Land派生的相对湿度(RH)和风速(WS)数据，分析地表城市热岛强度(SUHII)的昼夜年际变化、边界外扩梯度特征及其与建成环境和背景因子的统计关系。结果表明：2013~2023年主城区夏季白天SUHII均值为1.7779，变化范围为0.3867~3.0729；夜间均值为2.4887，变化范围为1.9135~3.2499，夜间均值高于白天且变化相对更稳定。白天SUHII线性趋势较弱，整体以年际波动为主；夜间SUHII表现为弱下降趋势。沿主城区边界外扩0~10 km梯度带，白天和夜间SUHII均随距离增加而明显衰减，其中1~5 km范围内变化最为显著，表现出较典型的“中心较强、外围减弱”空间结构；相比之下，MNDWI沿梯度带变化幅度较小。年度尺度相关分析表明，白天SUHII与RH和ISA ratio (不透水面比例)的相关程度相对较高但未达显著，夜间SUHII与景观格局指标，尤其是AI，呈较明确负相关。总体上，呼和浩特市主城区夏季SUHII具有明显昼夜差异，不同环境因子与SUHII的统计关联在昼夜尺度上存在差异，相关结果可为北方半干旱城市热环境监测与精细化调控提供参考。

Abstract: Taking the main urban area of Hohhot as the study area, this study analyzed the interannual day-night variations of surface urban heat island intensity (SUHII), its outward gradient pattern, and its statistical associations with built environment and background factors based on summer TRIMS LST data from 2013 to 2023, combined with GUB dynamic urban boundaries, GAIA built-up area data, MNDWI, and ERA5-Land-derived relative humidity (RH) and wind speed (WS). The results showed that the mean daytime SUHII was 1.7779, ranging from 0.3867 to 3.0729, whereas the mean nighttime SUHII was 2.4887, ranging from 1.9135 to 3.2499. Nighttime SUHII was higher than daytime SUHII and showed relatively more stable interannual variation. Daytime SUHII exhibited no evident linear trend and was mainly characterized by interannual fluctuations, while nighttime SUHII showed a weak decreasing trend. Along the 0~10 km outward gradient from the main urban boundary, both daytime and nighttime SUHII decreased significantly with increasing distance, with the most pronounced changes occurring within 1~5 km, indicating a typical spatial structure of stronger heat island intensity in the urban core and weaker intensity toward the periphery. In contrast, MNDWI varied only slightly along the gradient. Correlation analysis at the annual scale indicated that daytime SUHII was relatively more related to RH and ISA ratio, although these relationships were not statistically significant, whereas nighttime SUHII showed clearer negative correlations with landscape pattern metrics, especially AI. Overall, the summer SUHII in Hohhot exhibits evident day-night differences, and the statistical associations between SUHII and environmental factors differ between daytime and nighttime. These results provide a reference for thermal environment monitoring and refined regulation in semi-arid cities of northern China.