scholarly journals Long-Term Evolution of the SUHI Footprint and Urban Expansion Based on a Temperature Attenuation Curve in the Yangtze River Delta Urban Agglomeration

2021 ◽  
Vol 13 (15) ◽  
pp. 8530
Author(s):  
Fei Tao ◽  
Yuchen Hu ◽  
Guoan Tang ◽  
Tong Zhou
Keyword(s):  
Urban Heat Island ◽  
Yangtze River ◽  
Urban Expansion ◽  
Yangtze River Delta ◽  
Urban Agglomeration ◽  
Heat Island ◽  
The Yangtze River ◽  
Development Patterns ◽  
Urban Heat ◽  
The Yangtze River Delta

The rapid growth of urbanization and population has aggravated the urban heat island (UHI) effect in urban agglomerations. However, because scholars have so far focused mainly on the magnitude of the UHI effect, there is still a lack of research on the quantitative evaluation of the relationship between urban expansion and the degree of the UHI effect from the urban agglomeration perspective. This paper analyzed the spatiotemporal characteristics and the interactive mechanism of the surface urban heat island footprint (SUHI FP) in the Yangtze River Delta urban agglomeration (YRDUA). The summer footprints (FPs) of 27 cities were extracted using a logistics model, and the temporal trend was estimated by a standard deviation ellipse (SDE). Furthermore, the authors used the classical machine-learning k-means algorithm to cluster the temperature attenuation curves to reveal development patterns in different cities. The results showed that the degree of FP expansion during the daytime was more apparent than at night, the area of urban growth positively correlated with a city’s population level, and from 2005 to 2018 (the period of the study), the spatial evolution for all cities showed an overall trend from east to west. These cities were divided roughly into three development patterns by clustering their 2018 temperature attenuation curves. These findings can provide a scientific basis for formulating effective land-use policies by giving a deeper understanding of the spatiotemporal changes in the SUHI FPs and their relationship with land cover in the YRDUA.

scholarly journals Relieved Air Pollution Enhanced Urban Heat Island Intensity in the Yangtze River Delta, China

2019 ◽  
Vol 9 (12) ◽  
pp. 2683-2696
Author(s):  
Hao Wu ◽  
Tijian Wang ◽  
Qin’geng Wang ◽  
Nicole Riemer ◽  
Yang Cao ◽  
...  
Keyword(s):  
Air Pollution ◽  
Urban Heat Island ◽  
Yangtze River ◽  
Yangtze River Delta ◽  
River Delta ◽  
Urban Heat Island Intensity ◽  
Heat Island ◽  
The Yangtze River ◽  
Urban Heat ◽  
The Yangtze River Delta

scholarly journals Research on the Dynamics and Evolution of Regional Blue-green Space Driven by the Development of World-class Urban Agglomerations

2021 ◽  
Author(s):  
Ziwu Pan ◽  
Jun Zhu ◽  
Zhenzhen Liu ◽  
Fen Qin
Keyword(s):  
Yangtze River ◽  
Green Space ◽  
Yangtze River Delta ◽  
River Delta ◽  
Urban Agglomeration ◽  
Heat Island ◽  
The Yangtze River ◽  
Urban Agglomerations ◽  
Island Effect ◽  
The Yangtze River Delta

Abstract In recent years, the process of urbanization in China has accelerated, and changes in the underlying surface have caused the difference in average temperature between built-up areas and suburbs to increase, resulting in an urban heat island effect, which has become an important environmental issue for today's urban sustainable development. The Yangtze River Delta urban agglomeration region is the fastest-growing region in China, with economically developed and populous cities such as Shanghai, Nanjing and Suzhou. It has become one of the six major urban agglomerations in the world, and its heat island effect is particularly prominent. The single urban heat island phenomenon gradually evolves into the urban agglomeration heat island phenomenon with urbanization. However, the dynamic transfer process of key blue-green space landscapes that can alleviate land surface temperature (LST) and regional thermal environment (RTE) is still poorly understood, especially in the context of urban agglomerations. With the approval of the State Council on the development plan of the Huaihe River Ecological Economic Belt, the construction of which has been officially upgraded to a national strategy. The Eastern HaiJiang River and Lake Linkage Zone (EJRLLZ) emphasizes strengthening the docking and interaction with the surrounding areas such as the Yangtze River Delta and the Wanjiang City Belt. With the diffusion of the heat island effect of the Yangtze River Delta urban agglomeration, as one of the areas with great potential development around the world-class urban agglomeration, the rich water body and green space in the ERLLZ area are also destroyed and affected. Therefore, we take this region as a case to further quantify the impact of urbanization and urban agglomeration development on the dynamics and evolution of blue-green space.

scholarly journals Spatiotemporal Characterization of the Urban Expansion Patterns in the Yangtze River Delta Region

2021 ◽  
Vol 13 (21) ◽  
pp. 4484
Author(s):  
Ziqi Yu ◽  
Longqian Chen ◽  
Long Li ◽  
Ting Zhang ◽  
Lina Yuan ◽  
...  
Keyword(s):  
Yangtze River ◽  
Urban Expansion ◽  
Yangtze River Delta ◽  
River Delta ◽  
Urban Agglomeration ◽  
The Yangtze River ◽  
Delta Region ◽  
Gravity Center ◽  
Yangtze River Delta Region ◽  
The Yangtze River Delta

Characterizing urban expansion patterns is of great significance to planning and decision-making for urban agglomeration development. This study examined the urban expansion in the entire Yangtze River Delta Region (YRDR) with its land-use data of six years (1995, 2000, 2005, 2010, 2015, and 2018). On the basis of traditional methods, we comprehensively considered the four aspects of urban agglomeration: expansion speed, expansion difference, expansion direction, and landscape pattern, as well as the interconnection of and difference in the expansion process between each city. The spatiotemporal heterogeneity of urban expansion development in this region was investigated by using the speed and differentiation indices of urban expansion, gravity center migration, landscape indices, and spatial autocorrelations. The results show that: (1) over the 23 years, the expansion of built-up land in the Yangtze River Delta Region was significant, (2) the rapidly expanding cities were mainly located along the Yangtze River and coastal areas, while the slowly expanding cities were mainly located in the inland areas, (3) the expansion direction of each city varied and the gravity center of the urban agglomeration moved toward the southwest, and (4) the spatial structure of the region became more clustered, the shape of built-up land turned simpler, and fragmentation decreased. This study unravels the spatiotemporal change of urban expansion patterns in this large urban agglomeration, and more importantly, can serve as a guide for formulating urban agglomeration development plans.

scholarly journals Urbanization-induced urban heat island and aerosol effects on climate extremes in the Yangtze River Delta Region of China

2016 ◽  
Author(s):  
Shi Zhong ◽  
Yun Qian ◽  
Chun Zhao ◽  
Ruby Leung ◽  
Hailong Wang ◽  
...  
Keyword(s):  
Land Cover ◽  
Yangtze River ◽  
Yangtze River Delta ◽  
Heat Island ◽  
The Yangtze River ◽  
Synoptic Conditions ◽  
Urban Heat ◽  
Aerosol Effects ◽  
The Yrd ◽  
The Yangtze River Delta

Abstract. The WRF-Chem model coupled with a single-layer Urban Canopy Model (UCM) is integrated for 5 years at convection-permitting scale to investigate the individual and combined impacts of urbanization-induced changes in land cover and pollutants emission on regional climate in the Yangtze River Delta (YRD) region in eastern China. Simulations with the urbanization effects reasonably reproduced the observed features of temperature and precipitation in the YRD region. Urbanization over the YRD induces an Urban Heat Island (UHI) effect, which increases the surface temperature by 0.53 °C in summer and increases the annual heat wave days at a rate of 3.7 d/yr in the major megacities in the YRD, accompanied by intensified heat stress. In winter, the near-surface air temperature increases by approximately 0.7 °C over commercial areas in the cities but decreases in the surrounding areas. Radiative effects of aerosols tend to cool the surface air by reducing net shortwave radiation at the surface. Compared to the more localized UHI effect, aerosol effects on solar radiation and temperature influence a much larger area, especially downwind of the city-cluster in the YRD. Results also show that the UHI increases the frequency of extreme summer precipitation by strengthening the convergence and updrafts over urbanized areas in the afternoon, which favor the development of deep convection. In contrast, the radiative forcing of aerosols results in a surface cooling and upper atmospheric heating, which enhances atmospheric stability and suppresses convection. The combined effects of the UHI and aerosols on precipitation depend on synoptic conditions. Two rainfall events under two typical but different synoptic weather patterns are further analyzed and the results suggest that synoptic forcing plays a significant role in modulating the urbanization-induced land-cover and aerosol effects on individual rainfall event. Hence precipitation changes due to urbanization effects may offset each other under different synoptic conditions, resulting in little changes in mean precipitation at longer time scales.

scholarly journals Vegetation Response to Urban Landscape Spatial Pattern Change in the Yangtze River Delta, China

2019 ◽  
Vol 12 (1) ◽  
pp. 68 ◽  
Author(s):  
Yu Cao ◽  
Yucen Wang ◽  
Guoyu Li ◽  
Xiaoqian Fang
Keyword(s):  
Spatial Heterogeneity ◽  
Yangtze River ◽  
Urban Expansion ◽  
Yangtze River Delta ◽  
Urban Agglomeration ◽  
Vegetation Coverage ◽  
The Yangtze River ◽  
Vegetation Degradation ◽  
The Yangtze River Delta ◽  
Vegetation Variation

Urbanization has destroyed and fragmented large amounts of natural habitats, resulting in serious consequences for urban ecosystems over past decades, especially in the rapidly urbanizing areas of developing countries. The Yangtze River Delta Urban Agglomeration, which has experienced the fastest socioeconomic development in China, was selected as the study area. To explore the relationship between urbanization and vegetation dynamics at the agglomeration scale, the spatiotemporal characteristics of urban expansion and vegetation variation of the study area were evaluated by landscape spatial analysis, regression analysis, and trend analysis. The results show that the urbanization level of the study area exhibited a continuous upward trend, with Shanghai as the regional core city, and the level of urbanization gradually decreased from the center towards the periphery of the urban agglomeration. The overall urban expansion presented obvious landscape spatial heterogeneity characteristics and the emergence of new cities and towns enhanced landscape connectedness and created a more aggregated urban agglomeration. Noticeable spatiotemporal differences of vegetation variation were observed from 2004 to 2013. Areas with relatively low vegetation coverage showed a steady growth trend, while those with higher vegetation coverage reported a significant decreasing trend. The spatial heterogeneity analysis of the vegetation trend demonstrated that vegetation degradation was a dominant and inevitable process across the study area. However, some parts of the urban sprawl area, especially at the periphery of the metropolis, may experience a greening trend rather than a browning trend, indicating that urbanization does not necessarily lead to large-scale vegetation degradation. Although urbanization poses a negative impact on vegetation and physical environments, urbanization has not yet reduced a large area of vegetation at the regional level.

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