Numerical evaluation of enhanced green infrastructures for mitigating urban heat in a desert urban setting

The cities of desert climates are anticipated to recognize a synergy of urban heat island(UHI)and severe heat waves during summertime.To improve the urban thermal environment,the present study aims quantitatively explore a strategically designed network of vegetation patches called green infrastructure(GI)in subtropical desert cities such as Dubai.To achieve a more comfortable temperature environment,we built and simulated four GI situations with higher GI fractions,GI25,GI50,GI75,and GI100.Using a mesoscale urban model,the mosaic approach is utilized to test potential thermal improvement and urban climate impact,and a portion of each urban grid cell in the model domain is altered with various species of urban vegetation patches by 25%,50%,75%,and 100%.The daily peak reduction in ambient temperature at 17:00LT is similar to 0.0168℃ per unit of GI increase when compared to the untreated scenario;however,the maximum anticipated daytime summer temperature decline for GI25,GI50,GI75,and GI100 is 0.6℃,1.1℃,1.4℃,and 1.7℃,respectively.The associated reduction in nighttime ambient temperature per unit increase in the GI is 0.0432℃,with a maximum temperature drop of around 2.4℃ for the GI100 scenario.Increased GI reduces the height of the planetary boundary layer(PBL)by up to 468 m,which might lead to greater pollution concentrations.While GI-based cooling has a significant influence on delayed sea breeze and humidity,it may raise the risk of heat discomfort in the indoor building environment.This study adds to our understanding of the potential for GI mitigation as well as the seasonal impact of developing GIs on the desert urban boundary layer.

Optimized greenery configuration to mitigate urban heat:A decade systematic review

Urban vegetation is a nature-based solution for cooling cities.Under global warming and urban population growth,it is essential to optimize urban vegetation configuration in the urban area to bring maximum cooling benefit.This paper reviews 85 optimized urban vegetation configuration studies published from 2010 to 2020 to provide an insight into the most effective vegetation configuration for urban heat mitigation.Patterns and preferences in methods and the optimized greenery configurations are comprehensively analyzed.The results indicate that size,quantity,and layout of urban green space and the physiological characteristics and spatial arrangement of urban vegetation significantly influence their cooling effect.Additionally,two other research gaps were identified.First,more research needs to be done in southern hemisphere cities experiencing rapid urbanization and severe impacts of extreme weather.Second,a comprehensive method for quantifying interactions and cumulative effects of natural and artificial factors in the urban environment is required.Future study needs a holistic understanding of the interactive effects of vegetation spatial distribution on urban environment and climate for a more accurate analysis of optimal cooling greening layouts in large urban areas at multi-scales.