The use of green infrastructure and irrigation in the mitigation of urban heat in a desert city

Severe urban heat,a prevalent climate change consequence,endangers city residents globally.Vegetation-based mitigation strategies are commonly employed to address this issue.However,the Middle East and North Africa are under investigated in terms of heat mitigation,despite being one of the regions most vulnerable to climate change.This study assesses the feasibility and climatic implications of wide-scale implementation of green infrastructure(GI)for heat mitigation in Riyadh,Saudi Arabia—a representative desert city characterized by low vegetation coverage,severe summer heat,and drought.Weather research forecasting model(WRF)is used to simulate GI cooling measures in Riyadh’s summer condition,including measures of increasing vegetation coverage up to 60%,considering irrigation and vegetation types(tall/short).In Riyadh,without irrigation,increasing GI fails to cool the city and can even lead to warming(0.1 to 0.3℃).Despite irrigation,Riyadh’s overall GI cooling effect is 50% lower than GI cooling expectations based on literature meta-analyses,in terms of average peak hour temperature reduction.The study highlights that increased irrigation substantially raises the rate of direct soil evaporation,reducing the proportion of irrigation water used for transpiration and thus diminishing efficiency.Concurrently,water resource management must be tailored to these specific considerations.

Optimization designs of artificial facilities in deserts based on computational simulation

Sediment transport of sand particles by wind is one of the main processes leading todesertification in arid regions, which severely impairs the ability of mankind to produce and live by driftingsand into settlements. Optimization designs of artificial facilities have lately attracted extensive interest forhuman settlement systems in deserts because of their acceptable protection effect, convenience ofimplementation, and low material cost. However, the complexity of a settlement system poses challengesconcerning finding suitable materials, artificial facilities, and optimization designs for sand depositionprotection. In an effort to overcome these challenges, we propose a settlement system built with brick, solarpanel, and building arrays to meet the basic needs of human settlements in arid regions while preventingwind-sand disasters. The wind flow and movement characteristics of sand particles in the brick, panel, andbuilding arrays were calculated using computational fluid dynamics and discrete phase model. Theperformance of three types of arrays in wind-sand flow in terms of decreasing the wind velocity and sandparticleinvasion distance was evaluated. The results show that the wind velocity near the surface and thesand invasion distance were significantly decreased in the space between the brick arrays through properlyselected vertical size and interspaces, indicating that the brick arrays have an impressive sand fixing andblocking performance;their effective protection distance was 3–4 m. The building arrays increased the nearsurfacewind velocity among buildings, resulting in less deposition of sand particles. The solar panel arrayswere similar to the building arrays in most cases, but the deposition of sand particles on solar panels exerteda negative effect on energy utilization efficiency. Therefore, taking the optimal configuration of thesettlement system into consideration, this study concludes that (1) brick arrays, which were proven effectivein preventing sand particles, must be arranged in an upwind area;(2) solar panel arrays could accelerate thewind flow, so they are best to be arranged at the place where sand particles deposited easily;and (3) buildingarrays present a better arrangement in downwind areas.