Urban heat island (UHI) intensification has emerged as one of the most pressing environmental challenges faced by contemporary cities under the backdrop of global climate change [1]. The elevated urban temperatures caused by UHI have been linked to adverse impacts on human health, air quality degradation, and vegetation stress, particularly in densely built environments [2]. Given these challenges, Nature-based solutions (Nbs), including optimizing green spaces are increasingly recognized as a strategy for addressing climate challenges, achieving carbon neutrality, improving biodiversity and enhancing social well-being [3,4]. Urban green spaces (UGS), comprising both artificial and natural greening (e.g., parks, street trees, and forest), play a vital role in regulating the microclimate through evapotranspiration, shading, and photosynthesis, thereby offering natural cooling benefits [5,6,7]. As such, the strategic integration of UGS into urban planning is essential, not only for alleviating UHI effects but also for reducing heat-related health risks and air pollution, and promoting environmental justice [8]. Beyond their climatic functions, UGS also support a biophilic urban vision, fostering connections between people and nature that enhance psychological well-being and social cohesion [9]. Therefore, the planning and design of UGS are fundamental to building climate-resilient, equitable, and livable cities.

The spatial configuration of UGS has been increasingly recognized as a determinant of its ecological and thermal performance [7,10]. Studies have shown that not just the size, but also the shape, connectivity, and distribution of UGS, significantly influence their cooling effects on urban environments [6,11]. Larger, aggregated, patchy and complex-shaped patches tend to be effective in cooling, while no consensus was reached based on patch-level metrics [12]. Furthermore, it has been acknowledged that the relationship between UGS areas and its cooling capacity is nonlinear, meaning that when exceeding a certain threshold, the cooling effects will decline. [11,13]. Given the tension in urban land use and the fading cooling effects, the design of UGS cannot be inefficient, especially in high-density cities. It is thus necessary to deepen the understanding of the relationship between the geometric morphology and cooling effect of UGS at patch level.

Although landscape metrics are widely used to quantify the configuration and composition of UGS, these indices fall short in visualizing spatial morphology and ecological connectivity, especially in complex urban contexts [14,15,16]. Furthermore, with ongoing urbanization, UGS is becoming increasingly fragmented and spatially isolated, leading to reduced cooling potential, particularly at broader spatial scales [10,17,18]. However, most studies have focused on high-temperature zones, despite the fact that UHI intensity varies dynamically and that low-intensity areas may evolve into or merge with higher-intensity zones over time [7]. Therefore, while landscape metrics can derive morphological indicators of UGS patches for cooling effect analysis, they provide limited insight into spatial relationships between patches and their cumulative effects on urban thermal environments. This limits their utility for formulating systematic ecological planning strategies to mitigate UHI at the city scale.

Compared to landscape metrics, morphological spatial pattern analysis (MSPA) offers a more informative alternative, as it not only quantifies the size and shape of patches but also visualizes their spatial layout [19]. As a pixel-based image analysis technique, MSPA identifies explicit landscape elements (e.g., core zones, branches, and bridges) using mathematical morphology operations [20], enabling a refined classification of UGS components that are both ecologically functional and spatially coherent [19,21]. Its application across multiple spatial scales, ranging from block-level to regional contexts, has been demonstrated in prior studies [22]. MSPA has also been widely applied in the construction of ecological and thermal networks, helping to extract ecological sources [21] or delineate “cold islands” and “heat islands” in urban settings [10,14,23,24,25,26,27]. Such research illustrates the potential of MSPA-based network perspectives to identify spatial morphologies that enhance or weaken UHI mitigation. Studies recognized that core zones (area with large and cohesive green patches), deliver the most substantial cooling effects, whereas fragmented units such as branches or islets often lack sufficient ecological function [23,25,28]. However, these approaches often fail to fully specify patch-level design parameters, such as area, shape, or fragmentation, that are necessary to guide practical interventions. Additionally, a systematic understanding of how different UGS configurations, particularly core zones (relatively large green spaces patches), contribute to UHI mitigation across seasons remains underdeveloped. Prior studies have shown that seasonal variations in solar radiation, hydrothermal conditions, and vegetation phenology significantly affect the relationship between surface temperature and UGS characteristics [29,30].

Previous research has predominantly focused on either local patch-scale or broader city-wide analyses, rarely integrating both levels. Specifically, most of studies addressing individual intervention without a systematic evaluation to interpret multi-scale cooling mechanism [31]. This overlooks potential scale-dependent effects and cross-scale interactions between regional UGS morphology and localized cooling performance. Overall, there are two key knowledge gaps regarding the relationship between UGS morphology and LST: First, there is a lack of research examining how different configurations of UGS, especially core zones, perform in mitigating UHI across distinct seasonal conditions. Second, few studies have jointly analyzed UGS–LST relationships at both city-wide and patch levels, despite the inherent scale sensitivity of thermal processes.

Understanding the thermal dynamics of UGS under varying spatial configurations and seasonal contexts is essential for climate-resilient planning, particularly in compact, high-density cities vulnerable to extreme heat. To address these gaps, this study proposes a dual-scale analytical framework to assess the cooling effects of UGS in Macau, a subtropical island city characterized by intensive development and limited ecological space. Specifically, this study aims to: (1) investigate the seasonal relationship between distinct MSPA-derived green space components and land surface temperature (LST) at the city scale; (2) analyze how UGS patch morphology (area, perimeter, and shape) affects cooling performance at the patch level; and (3) identify and classify UGS patches based on their observed summer cooling performance and extract the key morphological traits associated with high- or low-performing patches. By integrating city-scale spatial decomposition with localized patch-level evaluation, this research contributes to a systematic understanding of UGS cooling dynamics and provides actionable insights for optimizing green infrastructure in subtropical high-density urban environments.