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Adaptation to prepare for adverse climate change impacts in the context of urban heat islands and outdoor thermal comfort (OTC) is receiving growing concern. However, knowledge of quantitative microclimatic conditions within the urban boundary layer in the future is still lacking, such that the introduction of adequate adaptation measures to increase OTC is challenging. To investigate the cooling performance of a water spraying system in a sub-tropical compact and high-rise built environment in summer under the influence of future (2050) climatic conditions, results from two validated models (Weather Research and Forecast (WRF) and ENVI-met models) have been used and analyzed. Our results indicate that the spraying system provides cooling of 2–3 °C for ambient air temperature at the pedestrian-level of the urban canyons considered here, which benefits pedestrians. However, improvement of the OTC in terms of the physiological equivalent temperature (PET—a better indicator of human thermal sensation) was noticeable (e.g., <42 °C or from very hot to hot) when the urban canyon was orientated parallel to the prevailing wind direction only. This implies that in order to improve city resilience in terms of heat stress, more holistic adaptation measures in urban planning are needed. This includes the introduction of more breezeways and building disposition to facilitate the urban ventilation, as well as urban tree arrangement and sunshades to reduce direct solar radiation to plan for the impact of future climate change.
Ka-Ming Wai; Lei Xiao; Tanya Tan. Improvement of the Outdoor Thermal Comfort by Water Spraying in a High-Density Urban Environment under the Influence of a Future (2050) Climate. Sustainability 2021, 13, 7811 .
AMA StyleKa-Ming Wai, Lei Xiao, Tanya Tan. Improvement of the Outdoor Thermal Comfort by Water Spraying in a High-Density Urban Environment under the Influence of a Future (2050) Climate. Sustainability. 2021; 13 (14):7811.
Chicago/Turabian StyleKa-Ming Wai; Lei Xiao; Tanya Tan. 2021. "Improvement of the Outdoor Thermal Comfort by Water Spraying in a High-Density Urban Environment under the Influence of a Future (2050) Climate." Sustainability 13, no. 14: 7811.
External exposure to gamma-photon irradiation from soil contamination due to nuclear power plant (NPP) accidents has significant contribution to human radiation exposure in the proximity of the NPP. Detailed absorbed doses in human organs are rarely reported in the literature. We applied the Monte Carlo Neutron Particle (MCNP) transport code to calculate and compare the absorbed doses in different human organs. The absorbed doses by gamma-photon radiation were from cesium-137 (137Cs) in soil contaminated by the two major NPP accidents. More serious and wide-spread impacts of the Chernobyl NPP accident on soil contamination in Ukraine, Belarus, Russia and countries as far as Sweden and Greece were due to the inland location, radiative plume transport pathway and high 137Cs emission strength (9 times the Fukushima emission). Based on our MCNP calculations, the largest absorbed dose was found in skin. The maximum calculated external 137Cs annual effective dose received from the Chernobyl accident was 10 times higher relative to the Fukushima accident. Our calculated effective doses at various influenced areas were comparable to those available in the literature. The calculated annual effective doses at areas near the Fukushima and Chernobyl NPPs exceeded the ICRP recommendation of 1 mSv yr−1.
Ka-Ming Wai; Dragana Krstic; Dragoslav Nikezic; Tang-Huang Lin; Peter K. N. Yu. External Cesium-137 doses to humans from soil influenced by the Fukushima and Chernobyl nuclear power plants accidents: a comparative study. Scientific Reports 2020, 10, 1 -8.
AMA StyleKa-Ming Wai, Dragana Krstic, Dragoslav Nikezic, Tang-Huang Lin, Peter K. N. Yu. External Cesium-137 doses to humans from soil influenced by the Fukushima and Chernobyl nuclear power plants accidents: a comparative study. Scientific Reports. 2020; 10 (1):1-8.
Chicago/Turabian StyleKa-Ming Wai; Dragana Krstic; Dragoslav Nikezic; Tang-Huang Lin; Peter K. N. Yu. 2020. "External Cesium-137 doses to humans from soil influenced by the Fukushima and Chernobyl nuclear power plants accidents: a comparative study." Scientific Reports 10, no. 1: 1-8.
Urban compact buildings impose large frictional drag on boundary-layer air flow and create stagnant air within the building environment. It results in exacerbating the street-level outdoor thermal comfort (OTC). It is common to perform in-situ measurements of the OTC in different urban forms and to study their relationship. However, it is impossible to do so from a planning perspective because of the absence of physical planned urban forms. Our objective was to quantify the thermal environment and OTC in different planned complex urban forms by well-validated numerical models. We coupled a computational fluid dynamics (CFD) model to an OTC (Rayman) model to study the OTC. The κ–ω SST turbulent model was adopted for the CFD simulations, with accuracy of the turbulent model validated by wind tunnel measurements. The highest calculated air temperature within the street canyon of a planned bulky urban form could reach more than 5 °C higher than the surrounding environment. Within the tested urban forms, our coupled model predicted mean radiant temperature comparable with measurements in the literature. The model also produced sensible street-level physiologically equivalent temperatures (PETs) when comparing with those listed in the human thermal sensation categories. In the morning, the predicted PETs within all the urban forms were lower than that in open areas, which indicated that the shading of buildings effectively reduced the PET increase due to solar irradiance. At noon, increases in PETs by more than 10 °C relative to the morning situation indicated that when the buildings acted as heat sources after insolation absorption, increase in the air temperature at the street intersection and in the street canyon made an important contribution to the receiver PETs. The reduction in building lengths and increase in the low-level porosity were the most effective ways to reduce the heat stress at the pedestrian-level.
Ka-Ming Wai; Chao Yuan; Alan Lai; Peter K.N. Yu. Relationship between pedestrian-level outdoor thermal comfort and building morphology in a high-density city. Science of The Total Environment 2019, 708, 134516 .
AMA StyleKa-Ming Wai, Chao Yuan, Alan Lai, Peter K.N. Yu. Relationship between pedestrian-level outdoor thermal comfort and building morphology in a high-density city. Science of The Total Environment. 2019; 708 ():134516.
Chicago/Turabian StyleKa-Ming Wai; Chao Yuan; Alan Lai; Peter K.N. Yu. 2019. "Relationship between pedestrian-level outdoor thermal comfort and building morphology in a high-density city." Science of The Total Environment 708, no. : 134516.
Urban tree planting is an important measure to provide micro-climate cooling (MCC) in megacities. However all of the studies available in the literature were focused on an ideal and clean environment where trees are not under environmental stresses. Here, we studied the effects of ambient ozone on the leaf area index (LAI) of trees and the resultant reduction in the effectiveness of trees in providing MCC. The ENVI-met model, which was well validated against our bio-meteorological measurements, was used to quantify the effect of reduced LAI on the cooling performance of trees in two urban sites of Hong Kong. Under the influence of ambient ozone stress with a high sky view factor (SVF), the sensible heat fluxes and surface temperatures were calculated to be at least 40 Wm−2 and 5 °C higher than the stress-free case, respectively. For the low-SVF situation with the LAI value decreased by 25%, the physiological equivalent temperature (PET) values indicated that heat-related physiological stress increased by 1 grade in the planted areas. With the increasing surface-level ozone concentrations in the southern China region, the current study provides useful information for cities to refine design schemes and plan specifications for urban greenery to cope with the problem.
Ka-Ming Wai; Zheng Tan; T.E. Morakinyo; Ta-Chien Chan; Alan Lai. Reduced effectiveness of tree planting on micro-climate cooling due to ozone pollution—A modeling study. Sustainable Cities and Society 2019, 52, 101803 .
AMA StyleKa-Ming Wai, Zheng Tan, T.E. Morakinyo, Ta-Chien Chan, Alan Lai. Reduced effectiveness of tree planting on micro-climate cooling due to ozone pollution—A modeling study. Sustainable Cities and Society. 2019; 52 ():101803.
Chicago/Turabian StyleKa-Ming Wai; Zheng Tan; T.E. Morakinyo; Ta-Chien Chan; Alan Lai. 2019. "Reduced effectiveness of tree planting on micro-climate cooling due to ozone pollution—A modeling study." Sustainable Cities and Society 52, no. : 101803.