Exploring the Meteorological Impacts of Surface and Rooftop Heat Mitigation Strategies Over a Tropical City

Abstract

Different heat mitigation technologies have been developed to improve the thermal environment in cities. However, the regional impacts of such technologies, especially in the context of a tropical city, remain unclear. The deployment of heat mitigation technologies at city‐scale can change the radiation balance, advective flow, and energy balance between urban areas and the overlying atmosphere. We used the mesoscale Weather Research and Forecasting model coupled with a physically based single‐layer urban canopy model to assess the impacts of five different heat mitigation technologies on surface energy balance, standard surface meteorological fields, and planetary boundary layer (PBL) dynamics for premonsoon typical hot summer days over a tropical coastal city in the month of April in 2018, 2019, and 2020. Results indicate that the regional impacts of cool materials (CMs), super‐cool broadband radiative coolers, green roofs (GRs), vegetation fraction change, and a combination of CMs and GRs (i.e., “Cool city (CC)”) on the lower atmosphere are different at diurnal scale. Results showed that super‐cool materials have the maximum potential of ambient temperature reduction of 1.6°C during peak hour (14:00 LT) compared to other technologies in the study. During the daytime hours, the PBL height was considerably lower than the reference scenario with no implementation of strategies by 700 m for super‐cool materials and 500 m for both CMs and CC cases; however, the green roofing system underwent nominal changes over the urban area. During the nighttime hours, the PBL height increased by CMs and the CC strategies compared to the reference scenario, but minimal changes were evident for super‐cool materials. The changes of temperature on the vertical profile of the heat mitigation implemented city reveal a stable PBL over the urban domain and a reduction of the vertical mixing associated with a pollution dome. This would lead to crossover phenomena above the PBL due to the decrease in vertical wind speed. Therefore, assessing the coupled regional impact of urban heat mitigation over the lower atmosphere at city‐scale is urgent for sustainable urban planning.

Insights Into Urban Heat Island and Heat Waves Synergies Revealed by a Land‐Surface‐Physics‐Based Downscaling Method

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Heat Mitigation in Cities: A Catalyst for Building Energy Saving

“…Super Cool Coatings exhibit sub-ambient surface temperatures and depending on the local climatic conditions can reduce the surface temperature of cities up to 15.0°C [18]. By lowering the surface temperature in the city, the height of the planetary boundary layer may decrease, resulting in reduced heat advection from the desert [31].…”

Analyzing the Land Surface Temperature Response to Urban Morphological Changes: A Case Study of the Chengdu–Chongqing Urban Agglomeration

“…In addition, the urban morphology has a significant impact on urban microclimates (Lai et al., 2019), such as LST (Monaghan et al., 2014), urban heat islands (Kusaka, Chen, et al., 2004), extreme precipitation in urban areas (Li et al., 2013), and the boundary layer structure (Salamanca et al., 2011). The LST is a key variable of the urban thermal environment and has been applied as a thermal environment indicator in many studies (Chen et al., 2022; Khan et al., 2023; Mohammed et al., 2021; Peng et al., 2016; Yang et al., 2019, 2021). Urban morphological changes affect the LST through physical changes including changes of net radiation, convective heat transfer, evapotranspiration, heat storage and other processes (Kim et al., 2021; Li, Zhang, et al., 2020; Nazarian & Kleissl, 2015; Yang & Li, 2015).…”