城市热岛效应是指城市温度比周围区域高的现象。城市发展过程中，大量自然地表被城市不透水面替代，显著改变了城市内部的能量平衡，加上城市居民社会经济活动带来大量热排放，使得城市热岛效应日益凸显。城市热岛效应会显著影响城市人居环境、居民的热舒适度和健康，因此成为学者关注的焦点。在卫星热红外遥感技术的支持下，国内外学者围绕城市热岛效应的时空特征、影响因素和形成机制，在众多城市开展了大量的案例研究与对比分析。但是在国家尺度，对于城市热岛效应的时空分布特征及其影响因素，尚缺乏深入的认知。据此，本文以全国面积大于10 km2的2036个独立城市斑块作为研究对象，采用基于遥感获取的地表温度、城市面积、景观形状指数、归一化植被指数等数据，基于地面观测获取的降水、气温、相对湿度、风速、细颗粒物浓度等数据，以及人口、国内生产总值等社会经济统计数据，定量分析我国城市热岛效应的分布特征及影响因素，并分别从气候特征、城市规模和城市形态的角度探究热岛效应的差异，探讨各影响因素的相对重要性以及关键因子对热岛的边际效应。研究可为通过调整城市规划改善热环境提供科学基础。研究的主要结论如下:
（1）热岛效应在白天具有显著的季节性差异，夏季的热岛强度最高（1.16 ± 0.84 ℃），冬季的热岛强度最低（-0.05 ± 0.65 ℃），在夜晚，季节差异不明显。热岛效应存在明显的空间异质性，在夏季白天主要表现为南方强北方弱，而夜晚与之相反。全局尺度的随机森林回归结果显示，影响夏季昼夜热岛效应的因素重要性顺序为：气象要素>城市化水平>土地覆盖>城市形态>空气污染。夏季白天，对热岛效应影响显著的前5个因素中，影响最大的是城/郊相对湿度的差异，其次是城/郊降水差异、城/郊归一化植被指数差异和城市面积，影响最小的是景观形状指数；夏季夜晚，显著影响的因素包括城/郊气温差异、城/郊人口密度差异、景观形状指数、城市面积、以及城/郊归一化植被指数差异。不同干湿区及温度带的热岛强度均存在显著差异（p < 0.05），且越湿润和温暖的城市，热岛效应越明显。不同区域，各因素对热岛效应的影响具有较大差异。城市面积在湿润区最为重要，当低于特定阈值（100 km2）时，它对热岛效应具有显著的正向影响；城/郊降水差异是半湿润区的重要因素，差异越大热岛效应越强；在半干旱区和干旱区中，城/郊归一化植被指数差异是影响热岛效应的主导因素，对热岛效应具有负向作用。城/郊人口密度差异在中温带、暖温带和南亚热带最为重要，当低于特定阈值（380人/km2、496人/km2、430人/km2）时，其对热岛效应具有显著的正向作用；在北亚热带，城/郊归一化植被指数差异是影响热岛效应的主导因素；城/郊相对湿度差异是中亚热带的重要因素，差异增加可导致热岛强度下降。
（2）不同规模的城市之间热岛强度存在显著差异（p < 0.05），且随着城市规模的增大，热岛效应越来越强。在夏季白天，对于不同规模的城市，对热岛效应影响最显著的因素均是城/郊降水差异，差异越大热岛效应越强。夏季夜晚，景观形状指数在微小城市和小城市最为重要；城/郊人口密度差异是中等城市的重要因素，其对热岛效应具有显著的正向作用；在较大城市和大城市，城/郊归一化植被指数差异是影响热岛效应的主导因素，其对热岛效应具有负向作用，可有效改善热环境。
（3）不同形态的城市之间，热岛强度具有显著差异（p < 0.05），且从Ⅰ型城市到Ⅴ型城市，随着景观形状指数的增大，热岛强度具有下降趋势，说明城市的形状越不规则、越复杂，热岛效应越弱。夏季白天，在Ⅰ型城市至Ⅳ型城市，城/郊降水差异是影响热岛效应最显著的因素；而城/郊相对湿度差异是Ⅴ型城市的重要因素，差异增加可导致热岛强度下降。夏季夜晚，城/郊归一化植被指数差异在Ⅰ型城市最为重要；城/郊人口密度差异在Ⅱ型城市和Ⅴ型城市最为重要，当低于阈值（470人/km2、492人/km2）时，其对热岛效应具有显著的正向影响；城市面积在Ⅲ、Ⅳ型城市最为重要，当低于阈值（38 km2、121 km2）时，其对热岛效应具有显著的正向作用。
本文围绕我国城市热岛效应开展研究，揭示了热岛效应的时空变化规律，识别了影响热岛效应的关键因素，可为改善城市热环境、提升居民福祉提供科学依据。

The urban heat island effect refers to the phenomenon where the temperature of a city is higher than that of the surrounding area. In the process of urban development, a large number of natural surfaces are replaced by impermeable surfaces, significantly changing the energy balance within the city. In addition, the social and economic activities of urban residents bring about a large amount of heat emissions, making the urban heat island effect increasingly prominent. The urban heat island effect will significantly affect the urban living environment, the thermal comfort and health of residents, thus becoming a focus of attention for scholars. With the support of satellite thermal infrared remote sensing technology, domestic and foreign scholars have conducted a large number of case studies and comparative analysis on the spatiotemporal characteristics, influencing factors, and formation mechanisms of urban heat island effect in many cities. However, at the national level, there is still a lack of in-depth understanding of the spatiotemporal distribution characteristics and influencing factors of urban heat island effects. Based on this, this article takes 2036 independent urban patches with a national area greater than 10km2 as the research object. Using remote sensing data such as surface temperature, urban area, landscape shape index, and normalized vegetation index, as well as ground observation data such as precipitation, temperature, relative humidity, wind speed, and fine particulate matter concentration, as well as socio-economic statistical data such as population and gross domestic product, the distribution characteristics and influencing factors of urban heat island effects in China are quantitatively analyzed. The differences in heat island effects are explored from the perspectives of climate characteristics, urban size, and urban form, and the relative importance of each influencing factor and the marginal effects of key factors on heat islands are explored. Research can provide a scientific basis for improving the thermal environment through adjusting urban planning. The main conclusions of the study are as follows:
(1) The heat island effect shows significant seasonal differences during the day, with the highest heat island intensity in summer (1.16 ± 0.84 ℃) and the lowest in winter (-0.05 ± 0.65 ℃). At night, seasonal differences are not significant. There is significant spatial heterogeneity in the heat island effect, which mainly manifests as strong in the south and weak in the north during the daytime in summer, while the opposite is true at night. The results of global scale random forest regression show that the importance order of factors affecting summer day night heat island effect is: meteorological factors > urbanization level > land cover > urban morphology > air pollution. During the summer daytime, among the top 5 factors that have a significant impact on the heat island effect, the difference in relative humidity between urban and suburban areas has the greatest impact, followed by differences in precipitation, normalized vegetation index, and urban area. The landscape shape index has the smallest impact; On summer nights, significant influencing factors include differences in urban/suburban temperature, population density, landscape shape index, urban area, and differences in normalized vegetation index between urban and suburban areas.There are significant differences (p < 0.05) in the intensity of heat islands between different wet and dry areas and temperature zones, and the more humid and warm the city, the more pronounced the heat island effect. There are significant differences in the impact of various factors on the heat island effect in different regions. The urban area is most important in humid areas, and when it is below a specific threshold (100 km2), it has a significant positive impact on the heat island effect; The difference in precipitation between urban and suburban areas is an important factor in semi humid areas, and the larger the difference, the stronger the heat island effect; In semi-arid and arid regions, the difference in normalized vegetation index between urban and suburban areas is the dominant factor affecting the heat island effect, and has a negative effect on the heat island effect. The difference in population density between urban and suburban areas is most important in the temperate, warm temperate, and subtropical regions. When it is below a specific threshold (380 people/km2, 496 people/km2, 430 people/km2), it has a significant positive effect on the heat island effect; In the northern subtropical region, the difference in normalized vegetation index between urban and suburban areas is the dominant factor affecting the heat island effect; The difference in relative humidity between urban and suburban areas is an important factor in the central and subtropical regions, and an increase in the difference can lead to a decrease in heat island intensity.
(2) There is a significant difference in heat island intensity between cities of different sizes (p < 0.05), and as the city size increases, the heat island effect becomes stronger. During the summer daytime, the most significant factor affecting the heat island effect for cities of different sizes is the difference in urban/suburban precipitation, with the greater the difference, the stronger the heat island effect. On summer nights, the landscape shape index is most important in micro cities and small cities; The difference in population density between urban and suburban areas is an important factor in medium-sized cities, which has a significant positive effect on the heat island effect; In larger and larger cities, the difference in normalized vegetation index between urban and suburban areas is the dominant factor affecting the heat island effect, which has a negative effect on the heat island effect and can effectively improve the thermal environment.
(3) There is a significant difference in heat island intensity between cities of different forms (p < 0.05), and as the landscape shape index increases, the heat island intensity shows a decreasing trend from Type I cities to Type V cities, indicating that the more irregular and complex the shape of the city, the weaker the heat island effect. During the summer daytime, the difference in urban/suburban precipitation is the most significant factor affecting the heat island effect in Type I to Type IV cities; The difference in relative humidity between urban and suburban areas is an important factor in Type V cities, and an increase in the difference can lead to a decrease in heat island intensity. On summer nights, the difference in normalized vegetation index between urban and suburban areas is most important in Type I cities; The difference in population density between urban and suburban areas is most important in Type II and Type V cities. When it is below the threshold (470 people/km2, 492 people/km2), it has a significant positive impact on the heat island effect; The urban area is most important in type III and IV cities, and when it is below the threshold (38 km2, 121 km2), it has a significant positive effect on the heat island effect.
This article focuses on the research of urban heat island effect in China, revealing the spatiotemporal variation patterns of heat island effect, identifying key factors affecting heat island effect, and providing scientific basis for improving urban thermal environment and enhancing resident well-being.