Effectiveness of green and cool roofs in mitigating urban heat island effects during a heatwave event in the city of Melbourne in southeast Australia

Abstract

This study evaluates the effectiveness of green and cool roofs as potential Urban Heat Island (UHI) mitigation strategies, and the impacts of these strategies on human thermal comfort during one of the most extreme heatwave events (27 th -30 th January 2009) in the city of Melbourne in southeast Australia. The Weather Research and Forecasting model coupled with the Single Layer Urban Canopy Model including different physical parameterization for various types of roofs (conventional, green and cool roofs) is used to investigate the impacts of green and cool roofs. Results show that the maximum roof surface UHI is reduced during the day by 1°C to 3.8°C by increasing green roof fractions from 30% to 90%, and by 2.2°C to 5.2°C by increasing the albedo of cool roofs from 0.50 to 0.85. Cool roofs are more efficient than the green roofs in reducing the UHI with maximum differences of up to 1.4°C. The reductions of the UHI vary linearly with the increasing green roof fractions, but slightly nonlinearly with the increasing albedo of cool roofs. The maximum reductions in wind speed are 1.25 m s -1 and 1.75 m s -1 with 90% green and cool roofs (albedo 0.85) respectively. While previous studies report that the advection of moist air from rural areas is a key mechanism, this study shows that this is not the case for the extreme heatwave event due to the very dry and warm conditions, and instead, convective rolls play a more important role. This study also shows that initial soil moisture for green roofs does not have a substantial impact on the UHI. Finally, green roofs improve human thermal comfort by reducing the Universal Thermal Comfort Index by up to 1.5°C and 5.7°C for pedestrian and roof surface levels respectively, and by 2.4°C and 8°C for cool roofs for the same levels.

A comprehensive review of sectorial contribution towards greenhouse gas emissions and progress in carbon capture and storage in Pakistan

“…In 1990, 30.58% of the population was residing in cities and 69.42% in rural areas but the proportion is predicted to reverse by 2050, as it is estimated that around 63.66% of the population will be residing in cities in Pakistan . As a result of rapid urbanization, the GHG emissions are increasing, resulting in climate extremes . Urban areas of Pakistan have been suffering from ever‐expanding unplanned developments that have a negative effect on the socio‐economic fabric of the society, and also on its environment .…”

“…10 As a result of rapid urbanization, the GHG emissions are increasing, resulting in climate extremes. 118 Urban areas of Pakistan have been suffering from ever-expanding unplanned developments that have a negative effect on the socio-economic fabric of the society, and also on its environment. 119 The expanding urbanization has resulted in high emissions from cement producing units, more vehicular use and more energy demand.…”

Impacts of future urban expansion on urban heat island effects during heatwave events in the city of Melbourne in southeast Australia

“…Following Imran et al . (), the first 24 hr of the simulation period is considered as spin‐up time and the remaining 72 hr of simulations are used for analyses.…”

Pengaruh Desain Berbasis Masyarakat Untuk Keberlanjutan Bangunan Hijau Menuju Arsitektur Sadar Energi

“…Keuntungan lain dari desain hijau diantaranya bangunan hijau juga berpotensi meminimalkan polutan yang ada di lingkungan perkotaan (Abbass, Sailor, & Gall, 2018;Xie, Lundholm, & Scott MacIvor, 2018). Desain hijau pada bangunan juga mempunyai manfaat efisiensi energi, yakni diperoleh melalui inovasi yang dikembangkan pada selubung bangunan, seperti implementasi pada atap hijau yang dapat mereduksi panas lingkungan (Imran, Kala, Ng, & Muthukumaran, 2018;Teotónio, Silva, & Cruz, 2018). Potensi desain hijau yang telah dilakukan di beberapa Negara dengan berbagai iklim, memiliki pengaruh yang positif dan luas, sehingga desain hijau merupakan konsep pembangunan yang berwawasan lingkungan.…”

“…Ketersediaan ruang hijau yang semakin berkurang dapat digantikan dengan dipertimbangkan melalui implementasi ruang hijau pada bangunan. Banyak manfaat diperoleh melalui bangunan hijau seperti implementasi atap hijau yang dapat mereduksi panas lingkungan (Imran et al, 2018;Teotónio et al, 2018), terbukti di Taman Semanggi yang pada akhirnya kurang berhasil, lingkungan terasa panas dan menyengat, sehingga kurangnya manusia untuk berkegiatan. Selain itu bangunan hijau juga berpotensi meminimalkan polutan yang ada di lingkungan perkotaan (Abbass et al, 2018;Xie et al, 2018), pada taman Jebres terasa suasana lingkungan yang asri dan segar dengan desain hijau yang optimal.…”