As one of the effective ways to study urban climate and environmental problems, the performance of numerical model could be improved in urban areas by enhancing the description of urban morphology. One of the largest challenges faced by researchers is the lack of real urban canopy parameters (UCPs) to represent urban morphological characteristics. In this study, the urban morphological parameters were estimated and a high‐resolution urban morphological parameter data set for the main cities in China was developed. The results show that the distribution of urban morphological parameters is of regional characteristics and cities in China are mainly dominated by low‐rise buildings. Chinese cities can be broadly divided into two types based on the probability distribution of building height: single‐peak and double‐peak. The number of low‐rise buildings in single‐peak cities is much larger than that of double‐peak cities, which contributes to the difference between the two types of cities. The equivalent street width of northern cities in China is higher than that of southern cities, and the equivalent building width is almost the same. However, the default UCPs of the Weather Research and Forecasting (WRF) model distort the morphology of Chinese cities. The sensitivity of the WRF model to urban morphological parameters was also investigated in Nanjing. Overall, our results indicate that urban morphological parameters have a significant influence on the energy balance process in cities and improve the performance of the WRF model in simulating the air temperature and canopy wind speed.

Understanding the urban thermal environment is vital for improving urban planning and strategy development when mitigating urban heat islands. However, urban thermal characteristics of local climate zones (LCZ) are different within cities and most studies lack regional perspective. This study explored surface thermal performances of cities in three urban agglomerations (Jing-Jin-Ji, Yangtze River Delta and Pearl River Delta) in China using MODIS land surface temperature (LST). Besides that, the diurnal and seasonal LST variations of LCZs are also studied. Moreover, the optimal LCZs for better urban cooling are also investigated in this study. Although the thermal distributions of LCZs are different in China, there are still some similar features. Our four key findings were as follows. (1) LCZs in China are well classified, with average overall accuracy of 82% being higher than that in some previous studies. (2) The LST of mid-rise (LCZ 2, 5) is higher than that of high- and low-rise buildings (LCZ 1, 3, 4, 6); and compact buildings are warmer than open buildings (LCZ 1–3 > LST 4–6) in summer of China. That shows both mid-rise and compact buildings are not beneficial to cool urban. In addition, LST variations at daytime and in summer are more significant than nighttime and other seasons. (3) LST differences within LCZs are significant at p < 0.05, and are most significant in Jing-Jin-Ji (JJJ). The LST difference within built types (LCZ 1–10) is more significant than within natural types (LCZ A–G), showing that built types alteration will be more effective for thermal environmental improvement. (4) Under the current population and urban area, increasing greenness and water area in compact high-rise buildings are the most effective strategies for urban cooling in all three urban agglomerations, with the largest reduction in LST of 4.11 K in JJJ. These findings will provide support for thermal environment mitigation, urban planning and sustainable urban development.

Surface energy balance (SEB) is a basic principle for all of the atmospheric circulation models, and surface soil heat flux (G₀) is an important component of energy balance. Plastic mulch is widely used in arid regions and alters land surface processes. In this study, hourly/daily G₀ and SEB over a mulched cotton field were analyzed in Northwest China. The net radiation beneath the mulch was simulated using transmitted down short-wave and down long-wave radiation through the mulch and up short-wave and up long-wave radiation from the soil beneath mulch. The results show that: (1) on the hourly time scale, G₀ in mulched soil is much smaller than that in non-mulched soil, day and night. This implies that mulch prevents energy going into the soil during the daytime and reduces soil heat loss at night. On the daily time scale, G₀ is similar in mulched and non-mulched soil. (2) During the seedling emergence period when the cotton is small, the energy balance closure over mulched soil (0.79) is slightly smaller than that over non-mulched soil (0.81). (3) Comparing to soil temperature in non-mulched soil, there’s a time offset on soil temperature in mulched soil at the same depth, which will bring a hysteresis on G₀ and SEB.

Global climate change and urbanization are causing temperatures to rise in cities, and the resulting heat island effect is becoming increasingly challenging. Urban trees play an essential part in a city’s ecosystems by offering a cooling impact through shading and transpiration; this results in reduced urban temperatures, increased thermal comfort for walkers, and an improved urban microclimate. This study integrates the cooling mechanisms, assessment methods, and socio-environmental effects of urban trees, proposing a comprehensive framework encompassing biophysical mechanisms, assessment models, and planning strategies to bridge the gap between research and practice. This review follows the PRISMA systematic review framework and synthesizes 128 eligible studies on the cooling effects of urban trees. Results show that trees reduce air temperature by approximately 0.5–5.8 °C and surface temperature by 2–12 °C, depending on canopy density, climate type, and measurement method. Morphological traits such as leaf area index (LAI > 3) and canopy density were the strongest predictors of cooling in humid and temperate climates, while physiological processes including transpiration enhanced cooling effectiveness under arid conditions. These findings provide quantitative thresholds and a conceptual framework that may support climate-adaptive urban planning and design.

The surface urban heat island intensity (SUHII) defined as the average temperature difference between urban and rural surfaces is mainly measured by satellite remote-sensing techniques. However, the satellite can only provide 2-D land surface temperature (LST) and not complete surface temperature (Tc which integrates the horizontal and vertical urban surface temperatures. The thermal anisotropy is very much prominent in the urban system; therefore, Tc may be more important than the 2-D LST for SUHII study. Furthermore, the 3-D LST measurement of a real urban is limited. In this letter, we measured a building's 3-D surface temperatures in Beijing, China, and the roof temperature (Troof was assumed as ``satellite measurement.'' The SUHII using Troof (SUHIITroof and Tc (SUHIITc, as well as air urban heat island intensity (AUHII) were compared. Results showed that: 1) the building's thermal anisotropy was evident with 18 K between roof and north wall at noon; 2) SUHIITc during the day was actually a cold island, while SUHIITroof was a heat island, caused by the different diurnal variation of Tc and Troof; and 3) The SUHIITroof has diurnal maximum value in daytime and minimum value in nighttime, which is opposite to AUHII. However, the diurnal pattern of SUHIITc is similar to AUHII which is like the shape of a spoon. This letter preliminarily explores the building's thermal anisotropy on SUHII and could be an important reference for urban SUHII study at microscale.