Analysis of Cooling and Humidification Effects of Different Coverage Types in Small Green Spaces (SGS) in the Context of Urban Homogenization: A Case of HAU Campus Green Spaces in Summer in Zhengzhou, China

Huawei Li,Yuchen Guo,Ruizhen He,Handong Meng,Guohang Tian,Sandor Jombach,Amoako-Atta Ernest,Yakai Lei

doi:10.3390/atmos11080862

Huawei Li, Yuchen Guo + Show 6 more

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https://doi.org/10.3390/atmos11080862

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Abstract

In the context of global warming, more and more cities are experiencing extreme Urban Heat Island (UHI) effects and extreme weather phenomena, but urban green spaces are proven to mitigate UHI. Most of UHI’s research focuses on the large scale and uses remote sensing methods, which do not reflect the dynamic characteristics in detail and do not detect internal influencing factors of the green space cooling effect. Therefore, this study focused on Small Green Spaces (SGS), carrying out the measurement of the meteorological parameters (temperature, relative humidity, wind direction, wind speed, photosynthetic radiation) of the 16 sites in four types of coverage (Impervious surface; Shrub-grass; Tree-grass; Tree-shrub-grass) in a university campus. At the same time, the coverage characteristic parameters, such as Canopy Density (CD), Leaf Area Index (LAI), Photosynthetically Active Radiation (PAR), Mean Leaf Angle (MLA), of each plot were analyzed and compared. The results showed that there were significant differences in temperature among different coverage types in SGS. The biggest difference was concentrated in the noon period when solar radiation is strongest during the day. The difference between the four types of coverage with vegetation at night was small. The maximum air temperature difference among the four types could reach 8.9 ℃ and the maximum relative humidity difference was 28.5%. The cooling effect of the multi-layer vegetation-covered (Tree-shrub-grass) area was the largest compared to the impervious surface, indicating that tree cover was the core factor affecting the temperature. Temperature and relative humidity had a close correlation with surface coverage types and some plant community characteristics (such as CD and LAI). The cooling and humidifying effects of plants were also related to PAR and leaf angle. The results provide suggestions for green space management and landscape design.

Highlights

Rapid urbanization has changed the structure of urban surfaces
The mean air temperature in August is 26.4 °C, the minimum air temperature in August is 11.9 °C, which appeared in the year of
The research results in this paper provide a scientific basis for characterizing the microclimate changes of green space

Summary

Introduction

Rapid urbanization has changed the structure of urban surfaces. According to statistics, more than50% of the global population is urban; it is estimated that by 2050, the proportion of the urban population will exceed 66% [1]. Due to the composition of the underlying surfaces of the city (urban roughness) such as impervious surfaces, buildings, and municipal facilities [3], have led to a change in the local climate that has resulted in problems such as urban heat island effects [4]. Due to the lack of consideration on the relations between urban forms and urban ventilation in city planning, the urban ventilation environment is getting worse and worse, increasing the intensity of the heat island effect. This drawback forms the backbone of enormous research interest in the adjustment of urban form and urban function, especially adjusting the microclimate to mitigate the heat island effect

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