Research has demonstrated that urban green spaces play a crucial role in mitigating the severe urban heat island (UHI) effect resulting from rapid urbanization. However, existing studies often suffer from limitations such as small sample sizes, a limited variety of green spaces, neglect of the cooling effect due to water bodies within the green spaces, and incomplete consideration of the overall cooling effect. These limitations may lead to inaccuracies in the research findings. Therefore, the present study takes the city of Xi'an, which is characterized by a severe heat island effect, as a case study. By comprehensively considering the cooling effects of various types of green spaces, the aim of this study is to explore the optimal green space scale for achieving efficient cooling. The results indicate that: (i) urban green spaces exhibit robust cooling effects, with variations observed among the various types of green spaces; (ii) the areas of both community parks without water and street gardens correlate with their respective cooling intensities and cooling outcomes. Additionally, with the exception of community parks with water, a non-linear correlation exists between the area of each type of green space and its cooling range; (iii) for community parks without water, and for street gardens, a larger area does not necessarily lead to a better outcome; the optimal areas of these green spaces are 3.44 and 0.83 hectares, respectively; (iv) for community parks with water, the area of internal water bodies should ideally be maintained at around 29.43% of the total green space area in order to achieve optimal cooling efficiency. In conclusion, this study introduces a new perspective and new optimization methods for urban green space planning, thereby offering scientific guidance to urban leaders, decision-makers, and planners in formulating effective development and management policies and urban planning schemes.

Research has demonstrated that urban green spaces play a crucial role in mitigating the severe urban heat island (UHI) effect. However, existing studies often suffer from limitations such as the neglect of the cooling effect of water bodies within the green spaces and incomplete considerations of the overall cooling effect. These limitations may lead to inaccuracies in the research findings. Therefore, the present study takes the city of Xi’an as a case study to explore the optimal green space size for achieving efficient cooling. The results indicate that (i) urban green spaces exhibit robust cooling effects, with variations observed among the various types; (ii) for community parks without water, and for street gardens, the optimal areas of these green spaces are 3.44 and 0.83 hectares, respectively; (iii) for community parks with water, the area of internal water bodies should ideally be maintained at around 29.43% of the total green space area in order to achieve an optimal cooling efficiency. In conclusion, this study introduces a new perspective and new optimization methods for urban green space planning, thereby offering scientific guidance to urban planners in formulating effective development and management policies and urban planning schemes.

With the acceleration of urbanization in China, urban problems have become increasingly serious, and have led to the concept of the Park City. This concept involves a consideration of the comprehensive value of green space in order to give full play to the maximum benefit of that green space and, thus, realize the sustainable development of the city. Therefore, an exploration of the optimal scale of urban green space will have theoretical and practical significance for the construction of the Park City and the rational allocation of urban land resources. Taking Xi'an as an example, the present paper comprehensively considers the socioeconomic and ecological benefits of urban green space, and calculates its optimal scale. The results indicate that: (i) in terms of the socioeconomic benefits alone, the per capita amount of green area in Xi’an needs to be larger than 11.08 m2, and there is no theoretical optimal size; (ii) in terms of ecological benefits alone, the per capita amount of green area in Xi’an needs to be greater than 22.98 m2; (iii) in terms of the combined socioeconomic and ecological benefits, the per capita amount of green area of Xi’an needs to be greater than 24.89 m2; (iv) the optimal scale for any city is more siginficantly impacted by the ecological effects than by the socioeconomic effects; (v) to satisfy the development and construction needs of various cities, with their individual characteristics, the optimal urban green space scale should be explored according to the target city’s developmental stage and land use situation. The methods and results of the present study are intended to provide a reference for the future construction of Park Cities in China, as well as the planning of green space systems in other cities globally, and to open new prospects for future research.

With the acceleration of urbanization, the urban heat island (UHI) effect has intensified. Urban green space can retard the UHI effect. However, most existing studies have only focused on hot regions, while little attention has been given to cold regions that also have summer heat protection requirements. Furthermore, existing researc has not classified urban green spaces according to the presence or absence of water, which can lead to inaccurate results. This paper takes four cities in cold regions of China as examples and studies the cooling effects of two different types of urban green space. The results indicate that in cold regions of China, green spaces containing water bodies have a stronger cooling effect than those without water. For green spaces without water, the cooling intensity is related to the background temperature and green space areas, while for green spaces containing water bodies, the area of the internal water body is the key influencing factor. Specifically, there is a threshold value of efficiency (TVoE) for the green space areas without water in cold region cities of China, which is approximately 0.52 ha, while there is no TVoE for the green space areas containing water bodies. Additionally, there is a TVoE for the water/land ratio of the green spaces containing water bodies of approximately 0.5. The methods and results of this study can provide a reference for future research and for urban planners and managers designing urban green spaces.