Mapping and Analyzing the Park Cooling Effect on Urban Heat Island in an Expanding City: A Case Study in Zhengzhou City, China

Abstract

The Urban Heat Island (UHI) effect has been extensively studied as a global issue. The urbanization process has been proved to be the main reason for this phenomenon. Over the past 20 years, the built-up area of Zhengzhou city has grown five times larger, and the UHI effect has become increasingly pressing for the city's inhabitants. Therefore, mitigating the UHI effect is an important research focus of the expanding capital city of the Henan province. In this study, the Landsat 8 image of July 2019 was selected from Landsat collection to obtain Land Surface Temperature (LST) by using Radiative Transfer Equation (RTE) method, and present land cover information by using spectral indices. Additionally, high-resolution Google Earth images were used to select 123 parks, grouped in five categories, to explore the impact factors on park cooling effect. Park Cooling Intensity (PCI) has been chosen as an indicator of the park cooling effect which will quantify its relation to park patch metrics. The results show that: (1) Among the five studied park types, the theme park category has the largest cooling effect while the linear park category has the lowest cooling effect; (2) The mean park LST and PCI of the samples are positively correlated with the Fractional Vegetation Cover (FVC) and with Normalized Difference Water Index (NDWI), but these are negatively correlated with the Normalized Difference Impervious Surface Index (NDISI). We can suppose that the increase of vegetation cover rate within water areas as well as the decrease of impervious surface in landscape planning and design will make future parks colder. (3) There is a correlation between the PCI and the park characteristics. The UHI effect could be mitigated by increasing of park size and reducing park fractal dimension (Frac_Dim) and perimeter-area ratio (Patario). (4) The PCI is influenced by the park itself and its surrounding area. These results will provide an important reference for future urban planning and urban park design to mitigate the urban heat island effect.Land 2020, 9, 57 2 of 17 countries and their rapid urban growth towards becoming a developed nation. Taking China as an example, according to the National Bureau of Statistics of China, the urbanization rate in China was 59.58% in 2018. This number is 12.58% higher than in 2008. This high-speed urbanization had led to widespread UHI problems in China [6]. With this rapid increase in urbanization has come an increase in energy consumption, with individuals attempting to reduce these adverse temperature effects (e.g., air conditioning, private vehicle usage). As a consequence, higher energy consumption based on coal power plants may result in air pollution, water pollution, and additional climate changes. More specifically, UHI compromised the health and life quality of citizens [7].Generally speaking, UHI can be measured by two methods: one of them is Surface UHI (SUHI); the other one is atmospheric UHI. Atmospheric UHI is defined into two different types: canopy layer UHI and boundary layer ...

6th Fábos Conference on Landscape and Greenway Planning

“…Huawei Li et al [3] map and analyze the role of parks effect on the urban heat island in Zhengzhou City China, which is an expanding urban area. The authors use remote sensing imagery to analyze 123 parks looking at the cooling effect on the dense expanding urban area of Zhengzhou City.…”

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

“…Compared with building shadows, plants not only provide shade, but also increase humidity [57,70]. Other studies had also drawn relevant conclusions; in Zhengzhou city (China), large parks have a significant cooling effect, and the cooling effect is positively related to the vegetation coverage inside of the park [29,71]. In the urban parks of Taipei, the average PCI during the daytime in summer is only 0.81°C but no consistent cooling effect was found in small parks (less than three hectares).…”

“…In addition to the physical properties of the above-mentioned and other urban constituent materials, the impact of green space layout is also proven [25,26]. At present, there are two main scales for studying the cooling effect of urban green space (UGS): one is large-scale research based on satellite imagery and meteorological data [27][28][29]; these studies applied indicators such as park cooling intensity (PCI) and green space cooling intensity (GCI) to quantify the cooling effect of UGS [22,30,31]. The other one is small-scale research through field observation and application of models [17,32,33].…”

Conceptual Planning of Urban–Rural Green Space from a Multidimensional Perspective: A Case Study of Zhengzhou, China

“…Green spaces play an active role in regulating the climate, such as by ventilation, cooling, and air purification [67,68], and many case studies on this have been published [69][70][71]. Ren et al pointed out that green ventilation corridors can promote urban ventilation, can introduce fresh air, and can alleviate the heat island effect [72]. Niu et al confirmed that green ribbon space has a significant cooling and humidifying effect [73].…”