scholarly journals Seasonal and Diurnal Variations in the Relationships between Urban Form and the Urban Heat Island Effect

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5909
Author(s):  
Ze Liang ◽  
Yueyao Wang ◽  
Jiao Huang ◽  
Feili Wei ◽  
Shuyao Wu ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Urban Form ◽  
Urban Heat Island Effect ◽  
Dominant Factor ◽  
Heat Island ◽  
Relative Contribution ◽  
Island Effect ◽  
Urban Geometry ◽  
Seasonal And Diurnal Variations ◽  
Urban Heat

At the city scale, the diurnal and seasonal variations in the relationship between urban form and the urban heat island effect remains poorly understood. To address this deficiency, we conducted an empirical study based on data from 150 cities in the Jing-Jin-Ji region of China from 2000 to 2015. The results derived from multiple regression models show that the effects of urban geometric complexity, elongation, and vegetation on urban heat island effect differ among different seasons and between day and night. The impacts of urban geometric factors and population density in summer, particularly those during the daytime, are significantly larger than those in winter. The influence of urban area and night light intensity is greater in winter than in summer and is greater during the day than at night. The effect of NDVI is greater in summer during the daytime. Urban vegetation is the factor with the greatest relative contribution during the daytime, and urban size is the dominant factor at night. Urban geometry is the secondary dominant factor in summer, although its contribution in winter is small. The relative contribution of urban geometry shows an upward trend at a decadal time scale, while that of vegetation decreases correspondingly. The results provide a valuable reference for top-level sustainable urban planning.

scholarly journals Study on Riparian Shading Envelope for Wetlands to Create Desirable Urban Bioclimates

Atmosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1348
Author(s):  
Abu Taib Mohammed Shahjahan ◽  
Khandaker Shabbir Ahmed ◽  
Ismail Bin Said
Keyword(s):  
Urban Heat Island ◽  
Urban Form ◽  
Water Surface ◽  
Inversion Layer ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Rapid Urbanization ◽  
Island Effect ◽  
Urban Heat ◽  
Riparian Shading

Climate change and rapid urbanization are adversely affecting the urban environment by exacerbating the widely reported urban heat island effect in Dhaka, Bangladesh. Two wetland areas with variable riparian shadings in the warm-humid conditions of urban Dhaka were investigated through field campaigns on microclimatic parameters for their cooling potential on the surrounding urban fabric. It was observed that an inversion layer of fully saturated air develops over the water surface of wetland, suppressing evaporation from the wetland water surface layer, which was effectively reducing the heat exchange between the water surface and the air layer above it through its action as an insulating vapor blanket. Due to this effect, the wetland was unable to render as a source of coolth for the surrounding overheated urban area. This effect of the inversion layer was more pronounced in the urban wetland without riparian shading either by the urban form or tree canopy. A multiphysics simulation study conducted on the selected urban wetlands indicates the effect of differential shading pattern on the relation between fetch and inversion layer thickness. This research hypothesizes that the wetland can act as an urban adaption measure against the urban heat island effect by potentially transforming them into an urban cooling island (UCI) towards a favorable urban bioclimate.

scholarly journals Study on Riparian Shading Envelope for Wetlands to Create Desirable Urban Bioclimates

2020 ◽  
Author(s):  
Abu Taib Mohammed Shahjahan ◽  
Khandaker Shabbir Ahmed ◽  
Ismail Bin Said
Keyword(s):  
Urban Heat Island ◽  
Urban Form ◽  
Water Surface ◽  
Inversion Layer ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Rapid Urbanization ◽  
Island Effect ◽  
Urban Heat ◽  
Riparian Shading

Climate change and rapid urbanization are adversely affecting the urban environment by exacerbating the widely reported Urban Heat Island effect in Dhaka, Bangladesh. Two wetland areas with variable riparian shadings in the warm-humid conditions of urban Dhaka had been investigated through field campaigns on microclimatic parameters for their cooling potential on the surrounding urban fabric. It was observed that an inversion layer of fully saturated air develops over the water surface of wetland, suppressing evaporation from the wetland water surface layer, which was effectively reducing the heat exchange between the water surface and the air layer above it through its action as an insulating vapor blanket. Because of this effect, the wetland was unable to render as a source of coolth for the surrounding overheated urban area. This effect of the inversion layer was more pronounced in the urban wetland without riparian shading either by urban form or tree canopy. A Multiphysics simulation study conducted on the selected urban wetlands indicates the effect of differential shading pattern on the relation between fetch and inversion layer thickness. This research hypothesizes that the wetland can act as an urban adaption measure against the urban heat island effect by potentially transforming them into Urban Cooling Island (UCI) towards a favorable urban bioclimate.

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