The urban heat island (UHI) effect is an increasingly prominent local climate issue in the process of global urbanization, significantly impacting human settlement health and energy consumption. Based on the China National Knowledge Infrastructure (CNKI) database, we searched and analyzed Chinese journal articles on the surface urban heat island (SUHI) effect published during 1980 and 2024. Using CiteSpace software, we conducted a visual analysis of publication trends and keywords to systematically summarize the research advances. We reviewed and discussed the research hotspots, including data sources, identification methods, and evaluation indicators related to the surface urban heat island effect. We also proposed the shortages and challenges in current research, such as identification accuracy, mechanism analysis, and impact assessment. More works should be strengthened in future research, including optimizing multi-source data integration with cross-validation, innovating multi-scale dynamic evaluation methods, and enriching multi-dimension impact assessment systems. By reviewing the development process of surface urban heat island effect research in China, we hoped to provide theoretical support and technical guidance for future research, contributing to the deepening and practical application of the research.

With the increase of high-rise buildings in major cities worldwide, exploring the effects of urban two-dimensional (2D) and three-dimensional (3D) morphology on land surface temperature (LST) has become the key to mitigating the urban thermal environment and optimizing urban planning. Using the area within the Third Ring Road of Changsha as a case, we extracted 13 urban 2D/3D morphological factors based on 2020 multi-source remote sensing data. We used Pearson correlation analysis to examine the relationship between LST and each factor, and used the XGBoost model and SHAP method to reveal their nonlinear impacts and contributions. The results showed that in 2020, high-temperature regions mainly concentrated in the building-dense central area of Changsha, while low-temperature areas predominantly located in the forest parks in the western and northeastern parts of the city, as well as along the Xiangjiang River. The normalized difference building index (NDBI), nighttime lighting (NTL) and proportion of construction land (PCL) exhibited significant positive correlations with LST, with correlation coefficients of 0.592, 0.537 and 0.446, respectively, indicating that urbanization exacerbated surface warming. In contrast, the normalized difference vegetation index (NDVI) and the sky view coefficient (SVF) showed significant negative correlation with LST, with correlation coefficients of -0.316 and -0.200, respectively, reflecting the important role of green space and open space in mitigating the urban heat island effect. NDBI, NTL, NDVI, and elevation (DEM) had the greatest influence on LST, contributing 60.9% of the total variance. These 2D/3D morphological factors exhibited complex nonlinear effects on LST. NDBI had the most significant warming effect in the range from 0 to 0.2. The warming effect of NTL tended to saturate when its intensity exceeded 40. The cooling effect of NDVI became more pronounced as it surpassed 0.5. DEM values between 50 and 150 m produced the most signifi-cant cooling effect. This study validated the effectiveness of the XGBoost-SHAP model in uncovering the nonlinear mechanisms through which urban 2D/3D morphological factors influenced LST, offering scientific insights for urban heat management and the development of green, low-carbon, and livable urbanization.

To reveal the impacts of motor vehicle lane layout on street-canyon air quality, we used computational fluid dynamics (CFD) numerical simulations to construct models for the transport and diffusion of traffic exhaust pollutants in urban street canyons under different lane layouts, and investigated the effects of the lane number and location on the distribution and diffusion of traffic exhaust pollutants in urban street canyons. The results showed that the number and location of motor vehicle lanes significantly affected the distribution and dispersion of pollutants in urban street canyons, but such impacts depended on the in-canyon airflow structure. Air quality within shallow street canyons was generally better than that of deep street canyons. Furthermore, air quality on the leeward side of shallow canyons was poorer than that on the windward side, whereas the spatial heterogeneity of air pollutant distribution in deep canyons differed due to the location of motor vehicle lanes. The configuration of motor vehicle lanes could change the spatial homogeneity of pollutant distribution within urban street canyons and promote the diffusion and removal of traffic exhaust pollutants, and consequently improve the in-canyon air quality. Controlling the number of lanes and placing them closer to the upstream building facilitated the improvement of air quality at the pedestrian level and on the windward side in shallow street canyons. Increasing the number of lanes and locating them nearer to the downstream building could reduce pedestrian-level air pollution risks at the leeward side in deep street canyons. Our findings could provide a scientific reference for numerical modeling of pollutant dispersion in street canyons and help develop urban design strategies for enhancing in-canyon air quality.

To understand the ecological adaptability of common garden plants, we analyzed the growth characteristics of 17 common garden plant species in the street green site and the campus green site. We measured microenvironmental characteristics, carbon sequestration, oxygen release, cooling and humidification of plants with the same diameter at breast height (herb was the height of the plant) in the two green sites. We used genotype main effect plus genotype-by-environment interaction biplot and Pearson correlation analysis to analyze the interaction between species identity and site type. The results showed that Sophora japonica, Ginkgo biloba, Prunus persica, Aesculus chinensis, Ligustrum × vicaryi, Berberis thunbergii, Ligustrum sinense and Sabina chinensis had significant differences in carbon sequestration and cooling benefits between the two site types. Under the same land area, S. chinensis showed the strongest carbon sequestration and cooling in the campus with the values of 33.79 g·m^-2·d^-1 and 2.30 ℃, respectively. Photinia × fraseri was the strongest species in the street, with values of 31.47 g·m^-2·d^-1 and 0.84 ℃, respectively. The average carbon sequestration and cooling capacity of plants was higher in the campus than in the street. Trees cooled and humidified better in the street. The microclimatic conditions of campus in the summer were more stable than the street, which was closer to the ideal environment for plant growth. To enhance the ecological function of the green sites in small- and medium-sized towns, we should select trees, shrubs and grasses with better carbon sequestration and cooling benefits, including S. japonica, Koelreuteria paniculata, Ligustrum lucidum, Prunus cerasifera, A. chinensis, Pinus bungeana, S. chinensis, L. sinense, Ligustrum × vicaryi, P. × fraseri and Ophiopogon japonicas.

Urban environments face numerous challenges, including an increase in impervious surfaces, intensification of heat island effect, and severe air pollution, which all affect urban vegetation phenology. We reconstructed the time series of MOD13Q1 enhanced vegetation index data for the Beijing-Tianjin-Hebei region during 2002-2021, extracted the vegetation phenology index based on the dynamic threshold method, and examined the dyna-mics of vegetation phenology under a urbanization gradient. The results showed that the start of growing season (SOS) occurred earlier in the southeastern region of Beijing-Tianjin-Hebei, the end of growing season (EOS) was later in the central and southwestern regions, and the growing season length (GSL) was extended in the central and southeastern regions. SOS had been advanced and EOS had been delayed in most areas of Beijing-Tianjin-Hebei, leading to a significant extension of the GSL. The phenological trends were generally consistent across different vegetation types, with specific manifestations varied. The advance in SOS was most pronounced in farmland. The delay in EOS was greatest in forests. The extension of GSL was most substantial in farmland. During 2002-2021, for every 10% increase in the proportion of impervious surface percentage (ISP), SOS advanced by 1.28 day, EOS was delayed by 1.33 day, and GSL was extended by 2.2 days. With increasing ISP, land surface temperature initially rose but stabilized once it exceeded 40%. As land surface temperature increased, SOS first advanced and then delayed (with an inflection point at 23 ℃), while EOS first delayed and then advanced (with an inflection point at 20 ℃). We speculated that the result was related to the coupling of light and temperature periods. The response degree of vegetation phenology under dynamic urbanization gradient showed significant differences. Surface temperature played an important role in driving the urban-rural phenological difference.