Abstract
Urban green spaces have been shown to decrease land surface temperature (LST) significantly. However, few studies have explored the relationships between urban green spaces and LST across different seasons at different spatial scales. In this study, using Changchun, China as a case study, landscape ecology and comparative approaches were employed quantitatively to investigate the effects of the composition and configuration of urban green spaces on the urban thermal environments. LST maps were retrieved from Landsat 8 Thermal Infrared Sensor (TIRS) data acquired on four dates that represented four different seasons, and detailed information of urban green spaces was extracted from high resolution imagery GF-1. Normalized differential vegetation index (NDVI) and six landscape metrics at patch, class, and landscape level were used to characterize the spatial patterns of urban green spaces. The results showed that urban green spaces did have significant cooling effects in all seasons, except for winter, but the effects varied considerably across the different seasons and green types, and seemed to depend on the NDVI and size of urban green spaces. Compared to shape metrics, the negative relationships between the LST and the area and the NDVI of urban green spaces were more significant. Both the composition and configuration of urban green spaces can affect the distribution of LST. Based on findings with one city, given a fixed area of urban green spaces, the number of green patches can positively or negatively affect the LST, depending on if the number is larger than a threshold or not, and the threshold varies according to the given area. These findings provide new perspectives, and further research is also suggested, to generate a better understanding of how urban green spaces affect the urban thermal environment.
Highlights
According to the United Nations, over half of the world’s population (54%) lived in urban areas in 2014, and this number is projected to increase to 66% by 2050 as a result of rapid urbanization [1].more people will suffer from urban heat island (UHI) effects, which are caused by dramatic changes in land use and land cover, energy use, and air-pollutant emissions [2,3,4]
The total area of green space is distributed across 115.84 km2 with 8287 patches, and all are located within the 5th Ring
Attached Green Spaces (AGS) was observed to have the largest total area followed by Ecological Green Spaces (EGS), Road Green Spaces (RGS), Park Green Spaces (PGS), Other Green Spaces (OGS), and Productive Plantation Green Spaces (PPGS)
Summary
According to the United Nations, over half of the world’s population (54%) lived in urban areas in 2014, and this number is projected to increase to 66% by 2050 as a result of rapid urbanization [1].more people will suffer from urban heat island (UHI) effects, which are caused by dramatic changes in land use and land cover, energy use, and air-pollutant emissions [2,3,4]. Forests 2017, 8, 153 to mitigate its negative impacts is one of the most important research issues for urban ecology and urban climatology Urban green spaces, such as open parks, forests, and grasslands, have been increasingly recognized as key components of urban planning [8,9,10,11]. Urban green spaces have been shown to form cool islands and improve outdoor thermal comfort throughout warm seasons, as well as significantly reduce environmental stress produced by heat island [12,13] They can provide critical ecosystem services that could improve residents’ health and wellbeing [13,14,15]. Urban green spaces can cool climates through two major processes: shading and by providing higher evapotranspiration [8,16,17]
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