1. Introduction
As an important carrier in urban renewal, pocket parks effectively improve the urban greening rate, improve the microclimate environment, and play an active role in regulating the outdoor thermal comfort of the human body and alleviating the urban heat island effect. Its flexible location, small scale, and discrete distribution enable it to be widely embedded in high-density built environments[1, 2].
In terms of ecological function, the pocket park not only beautifies the urban environment through the rational allocation of vegetation planting and landscape elements, but also provides convenient and accessible leisure, fitness and social space for the surrounding residents, significantly improving the quality of the living environment in high-density urban areas.
As an important urban green space, pocket park is an outdoor open space with flexible location, small area and uneven distribution. Different scholars have defined the concept of pocket park from different angles (Table 1).
Table 1
Definition of pocket park related concepts
|
Author/Source
|
Region
|
Definition
|
|
Robert Zion[3]
|
United States
|
Small outdoor open spaces located in the center of a high-density city are characterized by small area, freedom from noise, and a sense of security.
|
|
Zhang Wenying[4]
|
China
|
Small and scattered, distributed in urban open spaces, directly serving local residents.
|
|
Tan Shaohu et al.[5]
|
China
|
Scattered in patches throughout the city, it is a public open space that can be freely used by people.
|
|
Lei Xuejiao et al.[6]
|
China
|
Scattered or hidden in the urban texture structure of small and medium-sized urban open or semi-open space.
|
|
《Urban pocket park design guidelines》 T/CECA 20028—2023[7]
|
China
|
The area is less than or equal to 1hm ², and it is guided by people's needs. It uses outdoor space construction in various urban land uses to provide the public with services such as leisure, sports and fitness, and cultural science education. It is a small urban public space that displays the city's image and reflects local cultural characteristics.
|
Through combing the relevant literature at home and abroad, it is found that the research on the thermal comfort of urban park green space has been carried out earlier, and the results are relatively rich and mature. Li Yulong took the small-scale public space in the transition season of cold cities as the research object, conducted a multiple regression analysis on the microclimate parameters and thermal comfort evaluation, and explored the influence of various microclimate factors on the thermal comfort of square space, rest space and equipment activity space[8]; Tao Ying based on field investigation and measurement combined with software simulation analysis, analyzed the problems existing in the thermal comfort of the site, and put forward corresponding optimization measures for the improvement of thermal comfort in Chongqing micro-green space[9]; Liu Wenjing takes the pocket park in Guangzhou as the research object, summarizes the thermal comfort evaluation characteristics of various types of pocket parks, obtains the physical environment factors and use characteristics factors that affect the thermal comfort of pocket parks, and finally chooses the thermal comfort improvement measures suitable for pocket parks[10]; Federica R adopts a combination of subjective and objective methods, uses a wearable system to evaluate microclimate variables, and combines the mobile terminal questionnaire to compare the perceived data with subjective thermal comfort[11]; Siqi Zhou et al. by selecting 14 pocket parks in Shanghai, using a drone to obtain high-resolution canopy images (canopy coverage, average leaf height, leaf diversity, etc.), and simultaneously measuring Ts and Ta inside and outside the park, to calculate the Universal Thermal Climate Index (UTCI) to evaluate thermal comfort[12].
Although the construction of pocket parks in high-density urban environments is a significant social and environmental necessity, its practical promotion is still in its infancy. Although there have been several comprehensive studies, such as Zhang and Han comparing the thematic and geographical distribution of Chinese and English literature[13], Kerishnan and Maruthaveeran summarizing the factors affecting the use of pocket parks [14], there are still important gaps in the existing knowledge system, especially in the systematic methodological level of thermal comfort research, which restricts evidence-based planning and design decisions.
In order to systematically grasp the research progress and method evolution in this field, this paper focuses on the methodological system of pocket park thermal comfort research, and is committed to responding to the following core questions: What mainstream research methods have been formed in this field? How do these methods support the research goals of different stages? What are the characteristics and trends of its application? Based on this, this study uses a systematic literature review method, using 21 articles selected from the Web of Science and China National Knowledge Network (CNKI) databases as samples, and conducts a comprehensive analysis from four dimensions: time evolution, research objectives, thermal comfort evaluation indicators and research methods. The purpose is to build a clear methodological framework, provide theoretical reference and path selection basis for follow-up research, and provide scientific support for the low-carbon, healthy and humanized design of pocket parks.
2. Literature search Methods
In this study, Web of Science and CNKI were used as the main literature retrieval databases. In Web of Science and CNKI, the keywords "pocket park" and "pocket park thermal comfort" were used to search the literature in the related fields of building science and engineering, respectively. As of September 2025, a total of 94 papers related to environmental science were retrieved by the keyword "pocket park" in Web of Science, including 8 papers related to the topic of thermal comfort; in CNKI, 321 papers related to building science and engineering were retrieved by the keyword "pocket park", including 13 papers related to thermal comfort.
After screening, 21 papers were finally identified as the research objects, including journal papers, conference papers and dissertations. Among them, 8 papers in English were all from Web of Science; 13 papers in Chinese were all from China National Knowledge Network (Table 2). These papers are stored in the "Papers" folder and constitute the basic database of this study.
Table 2
Research collections in different databases
|
Database
|
Number of Studies
|
|
CNKI
|
13
|
|
Web of science
|
8
|
3. Literature results analysis and discussion
3.1. Time dimension
In the CNKI database, a total of 321 relevant papers in the field of building science and engineering were retrieved with the keyword "pocket park". According to the statistics of the number of papers published year by year, since the introduction of the concept of pocket park in our country in 2012, the number of relevant research papers has shown an increasing trend year by year, and has entered an accelerated growth stage since 2021. In the Web of Science database, 94 papers related to environmental science were retrieved with the keyword "pocket park". The statistical results show that the field began to appear in 2008 and entered a stage of rapid development by 2022.
Further searching in CNKI with the keyword "pocket park thermal comfort", 13 articles were obtained. The earliest relevant research was published in 2020, and the number of articles has increased year by year since then. In Web of Science, 8 relevant papers were retrieved with the keyword "pocket park thermal comfort". The earliest literature appeared in 2021, and the research sites were mostly concentrated in South East Asia. The number of relevant publications has shown a steady increase in recent years (Fig. 1).
3.2. Research Objectives Analysis
Through a systematic review of 21 related studies, it can be found that the current research on pocket park microclimate and thermal comfort has shown a clear stage of evolution. The field has gradually developed from an early basic empirical stage focusing on verifying whether its thermal environment improvement is "effective" to a new stage of in-depth exploration of "how to be more effective", "for whom", and "thermal comfort and multi-sensory synergy." In the past five years, researchers have not only continued to pay attention to the objective optimization of the physical environment, but also paid more and more attention to the comprehensive perception and actual behavioral experience of users. They have actively used quantitative tools and numerical simulation methods to analyze the mechanism of design elements, and are committed to building a systematic theoretical framework and differentiated design strategy to scientifically guide the planning and practice of pocket parks, and promote the mature development of research in the direction of diversification and application (Table 3).
The first stage is the "basic effect verification" stage (2020–2022), which mainly focuses on the basic verification of the ecological benefits of pocket parks[15], especially the cooling effect. The research in this stage aims to determine whether the pocket green space in high-density urban areas has a significant effect on alleviating urban heat islands and improving the local thermal environment[16, 17]. Taking Shanghai, Xi'an and other cities as cases, the study generally confirmed that the pocket park has considerable cooling and humidification capacity, laying a solid empirical foundation for its follow-up research.
The second stage can be summarized as the "mechanism analysis and factor quantification" stage (2022–2025). On the basis of clarifying the effect of its thermal environment improvement, scholars began to use numerical simulation tools such as ENVI-met to deeply analyze the specific mechanism of the impact of design elements such as tree canopy structure and green space layout mode on thermal comfort[2, 12, 18, 19]. The research focus of this stage shifted from utility verification to optimization strategy exploration, dedicated to seeking optimal design parameters in different development intensities and climate regions, providing scientific support for the realization of refined design.
The third stage is manifested as the research turn of "multi-sensory fusion and crowd focus" (2023–2025). This stage breaks through the limitations of traditional single physical indicators and turns to human-centered multi-dimensional perception research. Scholars not only focus on the comprehensive impact of environmental factors such as heat, sound, and air quality[20–22], but also introduce the theory of landscape ecology to explore the mechanism of psychological factors such as visual perception on thermal comfort judgment. At the same time, research begins to focus on the needs of specific groups such as children in cold regions[23], reflecting a profound shift in the research paradigm to humanization and refinement.
A
Table 3
Analysis of Literature Research Objectives
|
Classification
|
Title
|
Year
|
Research Objectives
|
|
Is it valid?
|
Study on the Influence of Pocket Park on Urban Thermal Environment and Tourists' Thermal Perception[15]
|
2020
|
To establish a thermal comfort design framework for pocket parks in humid and hot areas of Guangzhou, based on empirical evidence, to meet the differentiated needs of users.
|
|
Estimating the Cooling Effect of Pocket Green Space in High Density Urban Areas in Shanghai, China[16]
|
2021
|
To evaluate the effectiveness of pocket green space in high-density urban areas of Shanghai in alleviating heat island effect during summer daytime, and propose optimization strategies.
|
|
Pocket parks for human-centered urban climate change resilience: Microclimate field tests and multi-domain comfort analysis through portable sensing techniques and citizens' science[11]
|
2022
|
Through a "human-centered" approach, the microclimate conditions of the pocket park and their impact on users' subjective perception were comprehensively evaluated.
|
|
Study on Microclimate and Usage of Xiamen Pocket Park[17]
|
2022
|
The interaction between Xiamen pocket park space design and microclimate is studied to provide a basis for improving comfort and use vitality.
|
|
How to be more effective
|
Winter Utilization Rate and Thermal Environment Sensitivity Analysis of Guangzhou Pocket Park[24]
|
2022
|
Analyze the relationship between winter thermal environment and the utilization rate of pocket parks in order to enhance the spatial vitality of high-density urban areas.
|
|
Study on Environmental Thermal Comfort of Pocket Park in Guangzhou[10]
|
2022
|
Based on user needs and microclimate characteristics, a classification and thermal comfort design method for pocket parks in humid and hot areas of Guangzhou was established.
|
|
Environmental Effects from Pocket Park Design According to District Planning Patterns-Cases from Xi'an, China[19]
|
2022
|
Optimize the tree density and green space layout of pocket parks in different development intensity blocks to improve the summer thermal environment.
|
|
Study on Design Decision of Pocket Park Greening Structure Based on Thermal Comfort Evaluation - Taking a Park in a Hot Summer and Cold Winter Area as an Example[2]
|
2023
|
Quantify the impact of greening structure parameters on the thermal environment of pocket parks in hot summer and cold winter areas, and balance ecological benefits and ventilation needs.
|
|
Winter Comfort Evaluation and Optimization Strategy of Pocket Park in Harbin[25]
|
2023
|
The relationship between residents' activities and thermal comfort in Harbin winter pocket park is studied, and the optimization strategy in severe cold climate is proposed.
|
|
Study on thermal comfort optimization of high density urban pocket park[26]
|
2023
|
The synergistic effect of building cluster and landscape afforestation on the summer thermal comfort of pocket parks in hot summer and cold winter areas is analyzed, and a differentiated design method is proposed.
|
|
Cooling effect of the pocket park in the built-up block of a city: a case study in Xi'an, China[27]
|
2023
|
Quantify the impact of Xi'an Pocket Park on the surrounding thermal environment and optimize the internal design through simulation to improve the thermal environment.
|
|
Research on Thermal Comfort Control Technology of Pocket Park Based on Human Behavior Patterns[28]
|
2024
|
This paper studies the interaction between landscape characteristics, human behavior and thermal comfort of pocket parks in Guangzhou high density city, and proposes a thermal comfort regulation scheme.
|
|
Study on Planning and Design of Shenyang Pocket Park Based on Thermal Comfort[29]
|
2024
|
To explore the influence mechanism of Shenyang pocket park space environment on microclimate, and provide optimization strategies for high-density urban areas in cold regions.
|
|
Study on Thermal Comfort Optimization Strategy of Pocket Park in Changchun City Based on ENVI-met Simulation[18]
|
2024
|
The thermal comfort of different functional spaces in Changchun Pocket Park is studied through empirical and simulation, and the influence of landscape elements is quantified and optimization strategies are proposed.
|
|
Does the spatial configuration of urban parks matter in ameliorating extreme heat?[30]
|
2024
|
This paper studies the impact of urban park space configuration on microclimate improvement potential under extreme heat wave events, and provides a basis for efficient park design.
|
|
Vertical canopy structure dominates cooling and thermal comfort of urban pocket parks during hot summer days[12]
|
2025
|
To explore the specific contribution of canopy structure of pocket parks to cooling effect and thermal comfort improvement in high-density cities.
|
|
Who is it designed for?
|
Study on Children's Thermal Comfort in Pocket Park in Winter Based on Child-Friendly Method[23]
|
2024
|
Taking children as the core users, this paper studies how to improve the activity comfort and willingness of Shenyang Winter Pocket Park by adjusting subjective perception.
|
|
Thermal comfort and multi-sensory
|
Correlation between Summer Utilization Rate of Pocket Park and Thermoacoustic Environment under High Temperature and Heat Wave[20]
|
2023
|
The built characteristics and thermoacoustic environmental quality of the pocket park in Hongshan District of Wuhan were analyzed, and its influence on the utilization rate under normal and heatwave weather was studied.
|
|
Tactical urban pocket parks (TUPPs) for subjective and objective multi-domain comfort enhancement[31]
|
2024
|
To evaluate the effectiveness of small parks (TUPPs) implanted through "tactical urbanism" interventions in improving urban thermal environments.
|
|
The Influence Mechanism of Visual Perception on Thermal Comfort Judgment - Taking Urban Pocket Parks as an Entry Point[21]
|
2025
|
From the perspective of landscape ecology and visual perception, this paper studies how visual information affects people's judgment of thermal comfort in pocket parks.
|
|
Effect of thermal-acoustic-air quality composite environments on overall comfort of urban pocket parks considering different landscape types[22]
|
2025
|
To explore the comprehensive effects of heat, sound and air quality on overall comfort in winter pocket parks, and the role of different landscape types.
|
3.3. Analysis of Thermal Comfort Evaluation Index
The core of outdoor thermal environment and comfort research lies in the selection of evaluation indicators, which are directly related to the accuracy and applicability of the research conclusions. Through a systematic analysis of 21 related studies, it is found that a multi-dimensional and systematic index evaluation system is currently widely used in this field, aiming to comprehensively capture the comprehensive impact of the complex environment in humid and hot areas on the human body (Fig. 2).
First, the comprehensive heat index has become the absolute mainstream and core tool for quantifying outdoor thermal comfort. Among them, the physiological equivalent temperature (PET) and the universal thermoclimatic index (UTCI) are the most widely used, because they can integrate the four key environmental parameters of air temperature, humidity, wind speed and mean radiation temperature, and convert complex climatic conditions into intuitive physiological temperature or thermal sensation levels, so as to achieve accurate assessment of the human body's heat stress response[2, 19, 27–29]. At the same time, wet-bulb black-bulb temperature (WBGT) has been adopted by several studies as an exclusive evaluation index for thermal safety and heat stress risk due to its authority in the field of occupational health and safety[15, 24], which is used to define the health risk threshold of outdoor activities in extreme heat environments.
Secondly, the multivariate methodology that combines subjective and objective is a significant feature of current research. Relying solely on physical measurements or simulations is no longer sufficient to fully reveal the essence of thermal comfort. Most studies collect objective environmental data (such as temperature, humidity, wind speed, average radiant temperature) or calculate comprehensive indices, and use subjective questionnaires (such as thermal sensation voting TSV, thermal comfort voting TCV, and overall comfort OCV) in parallel to obtain users' real-time perception[10, 11, 17]. This "data-perception" cross-validation strategy greatly enhances the reliability and persuasiveness of research conclusions.
Furthermore, the evaluation dimension shows a deepening expansion from "physical" to "human-oriented". Frontier research is no longer limited to traditional physical and perceptual indicators, but has begun to explore the application of behavioral and physiological proxy indicators. For example, by observing the spatiotemporal distribution of the population[25], activity type and dwell time to reflect comfort preferences[28]; even with the help of physiological measurement technologies such as eye tracking and electric skin activity (EDA), the subconscious emotional stress response induced by visual stimuli is detected[21], marking the research paradigm towards a deeper subjective response mechanism of the human body.
To sum up, the current outdoor thermal comfort research has formed a mature and multi-faceted evaluation system with PET and UTCI as the core, WBGT as a safety supplement, subjective and objective integrated questionnaires as verification, and gradually expanding to behavioral and physiological indicators. This system provides a solid methodological foundation for scientific evaluation and improvement of urban outdoor thermal environment.
3.4. Analysis of research methods
In recent years, the research methods on the microclimate and thermal comfort of pocket parks have shown a trend of diversification and cross-integration, and have formed a relatively systematic method system. The 21 studies reviewed in this paper show significant characteristics of diversification, cross-fertilization and systematization in research methods, which can be mainly classified into the following six types.
First, empirical correlation analysis is the core approach to lay the foundation for research. This method collects subjective and objective data simultaneously through field measurement (such as temperature and humidity, wind speed, radiation), behavioral observation (such as flow of people, activity type) and questionnaire survey (such as thermal feeling vote TSV, thermal comfort vote TCV), and then uses statistical methods (such as correlation analysis, regression analysis) to reveal its internal connection. For example, some studies have identified the significant impact of WBGT and PET on space utilization and users' subjective feelings through the framework of "empirical investigation-statistical classification-association analysis"[10, 15]; some studies have further established a quantitative relationship model between microclimate parameters and user behavior and comfort[12, 28, 29].
Secondly, digital simulation-driven research has become the mainstream method for in-depth exploration and optimization of design. With the help of microclimate simulation software such as ENVI-met, researchers can build high-precision models to compare PET and UTCI under different design scenarios (e.g. vegetation configuration, underlying surface materials, spatial layout)[2, 25, 26, 30]. It is worth noting that orthogonal experimental designs are widely used to improve simulation efficiency. This method can scientifically identify the key influencing factors and their optimal level combinations with the least number of simulations through Range Analysis, which significantly improves the technical depth and scientific nature of the research.
Furthermore, remote sensing and spatial analysis provide a macro perspective for the study. Based on GIS platforms and remote sensing images (e.g. Landsat), such studies quantify the cooling effect of green space (e.g. cooling intensity, extent) at the urban scale by retrieving land surface temperature (LST) and calculating landscape pattern index, and analyze its relationship with green space area and surrounding pattern[16, 31].
In addition, controlled experiments and the application of emerging technologies enrich the data collection dimension. Research has captured more fine environmental parameters and human physiological and behavioral feedback in the laboratory or real environment by setting up cgroups or introducing multi-source sensing technologies such as wearable sensors and eye trackers, revealing the rules that are difficult to find with traditional methods[11, 21, 31].
Finally, a significant trend is the systematic integration of multiple methods. Many studies follow a comprehensive technical approach of "field research-data analytics-simulation verification"[12, 18, 23, 24]. First, problems are identified and initial correlations are established through empirical research, and then optimization strategies are predicted and verified by digital simulation methods, thus forming a complete closed-loop research chain from diagnosis, analysis to intervention, which greatly enhances the scientific and practical value of research results.
To sum up, the research methods in this field are moving from single to complex, from description to prediction, showing the characteristics of multi-disciplinary intersection, subjective and objective combination, macro and micro integration, and jointly promoting the deepening and refinement of the thermal environment research of urban small and micro green spaces.
4. Conclusions
This study systematically combs 21 Chinese and foreign literatures in Web of Science and CNKI databases, and comprehensively analyzes the current research status in the field of urban pocket park microclimate and thermal comfort from four dimensions: time evolution, research objectives, thermal comfort evaluation indicators and research methods. The research process follows a systematic framework of literature retrieval, screening and analysis, aiming to reveal the development context, core issues and methodological system of this field.
The main conclusions of this study are as follows: First, the research in this field has shown a clear stage of evolution. From the basic empirical stage of verifying whether cooling is "effective" in the early stage, through the mechanism analysis and factor quantification stage of exploring "how to be more effective", it has developed into a new stage of refinement and humanization focusing on "who is designed for" and "thermal comfort and multi-sensory coordination". Second, in terms of evaluation indicators, PET and UTCI have been formed as the core, WBGT is a safety supplement, and a diversified and systematic evaluation system integrating subjective questionnaire voting, behavioral observation and even physiological measurement has been formed. Third, in terms of research methods, it shows the distinct characteristics of multi-disciplinary cross-integration, establishing the two mainstream paradigms of "empirical correlation analysis" and "digital simulation-driven", and emerging efficient tools such as "orthogonal experimental design" and a comprehensive hybrid research path of "field research-simulation verification".
The significance of this study is that through a systematic review, the theoretical framework and methodological system of pocket park thermal comfort research are sorted out and clarified, which provides a clear guide for subsequent researchers to quickly grasp the whole picture of the field and choose an appropriate research path. The research paradigm and conclusion described above have important practical reference value for scientifically guiding the planning and design of pocket parks in high-density urban environments and improving their climate adaptability and spatial vitality.
However, this study also has certain limitations. Firstly, the literature search mainly focuses on two databases, Web of Science and CNKI. Although it can cover the core literature in Chinese and English, it is inevitable to miss some related studies published on other platforms or languages. Secondly, due to the number of papers finally included in the analysis (21), the generality of the statistical laws and trends obtained needs to be further verified by more research samples.
Based on the progress and shortcomings of current research, future research directions can be deepened from the following aspects: 1) Expand the geographical and climate scope of research, strengthen the regionalization and differentiation research in different climate zones such as cold and drought, and different urban cultural backgrounds; 2) Develop dynamic and personalized thermal comfort evaluation models, integrate time series analysis and personal physiological parameters, and more accurately reflect the true thermal experience; 3) Deepen the research on multi-sensory interaction mechanisms to further clarify the synergistic or antagonistic effects of environmental factors such as heat, sound, light, and visual landscape on overall comfort; 4) Promote research results to design guidelines and intelligent interventions
Transformation, using digital twin, real-time monitoring and other technologies to achieve dynamic perception and adaptive regulation of the pocket park environment.