Interaction of Urban Rivers and Green Space Morphology to Mitigate the Urban Heat Island Effect: Case-Based Comparative Analysis.

Yunfang Jiang,Hongxiang Wang,Tiemao Shi,Jing Huang

doi:10.3390/ijerph182111404

Abstract

The spatial morphology of waterfront green spaces helps generate cooling effects to mitigate the urban heat island effect (UHI) in metropolis cities. To explore the contribution and influence of multi-dimensional spatial indices on the mitigation of UHIs, the green space of the riparian buffer along 18 river channels in Shanghai was considered as a case study. The spatial distribution data of the land surface temperature (LST) in the study area were obtained by using remote sensing images. By selecting the related spatial structure morphological factors of the waterfront green space as the quantitative description index, the growth regression tree model (BRT) was adapted to analyze the contribution of various indexes of the waterfront green space on the distribution of the LST and the marginal effect of blue–green synergistic cooling. In addition, mathematical statistical analysis and spatial analysis methods were used to study the influence of the morphological group (MG) types of riparian green spaces with different morphological characteristics on the LST. The results showed that in terms of the spatial structure variables between blue and green spaces, the contribution of river widths larger than 30 m was more notable in decreasing the LST. In the case of a larger river width, the marginal effect of synergistic cooling could be observed in farther regions. The green space that had the highest connectivity degree and was located in the leeward direction of the river exhibited the lowest LST. In terms of the spatial morphology, the fractional cover values of the vegetation (Fv) and area (A) of the green space were the main factors affecting the cooling effect of the green space. For all MG types, a large green patch that had a high green coverage and connectivity degree, as well as was distributed in the leeward direction of the river, corresponded to the lowest LST. The research presented herein can provide methods and development suggestions for optimizing spatial thermal comfort in climate adaptive cities.

Highlights

The contribution ratios of various impact factors of the green space to the land surface temperature (LST) were calculated in the buffer zone of Width-I rivers by using the Boosted Regression Tree (BRT) model (Figure 6)
The Fv, area, and landscape shape index (LSI) were used to describe the morphology of green space
The total contribution ratio of the Fv and area was as high as 67.50%, which indicated that large-scale vegetation coverage had a significant impact

Summary

Introduction

With the expansion of urban areas and intensification of the urbanization process, the urban heat island (UHI) effect is becoming a significant urban issue. Natural surfaces, such as vegetation areas and riparian areas, are being replaced by impervious surfaces, resulting in increased long-wave radiation [1,2,3]. Impervious surfaces absorb more solar radiation due to their low reflectivity and high absorptivity, thereby generating a higher land surface temperature (LST) that increases the air temperature, due to the increased long-wave radiation, and induces the urban heat island effect [4,5,6,7].

Results

Discussion

Conclusion