scholarly journals Use of Cool Roofs and Vegetation to Mitigate Urban Heat and Improve Human Thermal Stress in Melbourne, Australia

2018 ◽  
Vol 57 (8) ◽  
pp. 1747-1764 ◽  
Author(s):  
Stephanie J. Jacobs ◽  
Ailie J. E. Gallant ◽  
Nigel J. Tapper ◽  
Dan Li
Keyword(s):  
Thermal Stress ◽  
Heat Wave ◽  
Urban Canopy ◽  
Vegetation Coverage ◽  
Cool Roof ◽  
Urban Heat ◽  
Nighttime Temperatures ◽  
Individual Strategies ◽  
Cool Roofs ◽  
The City

AbstractThe ability of cool roofs and vegetation to reduce urban temperatures and improve human thermal stress during heat wave conditions is investigated for the city of Melbourne, Australia. The Weather Research and Forecasting Model coupled to the Princeton Urban Canopy Model is employed to simulate 11 scenarios of cool roof uptake across the city, increased vegetation cover across the city, and a combination of these strategies. Cool roofs reduce urban temperatures during the day, and, if they are installed across enough rooftops, their cooling effect extends to the night. In contrast, increasing vegetation coverage reduces nighttime temperatures but results in minimal cooling during the hottest part of the day. The combination of cool roofs and increased vegetation scenarios creates the largest reduction in temperature throughout the heat wave, although the relationship between the combination scenarios is nonsynergistic. This means that the cooling occurring from the combination of both strategies is either larger or smaller than if the cooling from individual strategies were to be added together. The drier, lower-density western suburbs of Melbourne showed a greater cooling response to increased vegetation without enhancing human thermal stress due to the corresponding increase in humidity. The leafy medium-density eastern suburbs of Melbourne showed a greater cooling response to the installation of cool roofs. These results highlight that the optimal urban cooling strategies can be different across a single urban center.

Design of a Cool Color Glaze for a Solar Reflective Tile

2014 ◽  
Vol 92 ◽  
pp. 159-167
Author(s):  
Chiara Ferrari ◽  
Alberto Muscio ◽  
Cristina Siligardi ◽  
Tiziano Manfredini
Keyword(s):  
Chemical Durability ◽  
Inorganic Pigments ◽  
Heat Island ◽  
High Chemical ◽  
Cool Roof ◽  
Island Effect ◽  
Solar Reflectance ◽  
Thermal Emissivity ◽  
Urban Heat ◽  
Cool Roofs

One of the most common materials-measures to counteract Urban Heat Island Effect can be identified in cool roof: white surface characterized by high solar reflectance and high thermal emissivity. One of the problems for the realization of cool roof is the difficult matching of white color with urban planning needs. In order to better integrate cool roofs into skylines cool colors were developed integrating pigments into cool roof surfaces. Cool roof market is actually dominated by organic based products with optimal solar performances but low durability against ageing. The use of ceramic-based products is crucial in the design of a new durable cool roof thanks to their naturally high thermal emissivity (ε=0.90) and their high chemical durability. The development of a new ceramic-based product made by a traditional porcelain stoneware tile as support, an inorganic engobe was started in the last years. In order to complete the product with a suitable glaze, eight different inorganic pigments were added to three different glazes, each one characterized by different surfaces features. Even if the addition of glazes, and pigments decrease the reflectance values of the solar reflective engobe, some promising results were achieved in this study especially regarding warm colored glazes.

scholarly journals Hotterdam: How space is making Rotterdam warmer, how this affects the health of its inhabitants, and what can be done about it

2015 ◽  
Author(s):  
Frank van der Hoeven ◽  
◽  
Alexander Wandl ◽  
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Heat Wave ◽  
Surface Energy Balance ◽  
The Elderly ◽  
Research Project ◽  
Adaptation Measures ◽  
Urban Heat ◽  
Physical Features ◽  
The City

Heat waves will occur in Rotterdam with greater frequency in the future. Those affected most will be the elderly – a group that is growing in size. In the light of the Paris heat wave of August 2003 and the one in Rotterdam in July 2006, mortality rates among the elderly in particular are likely to rise in the summer. METHOD The aim of the Hotterdam research project was to gain a better understanding of urban heat. The heat was measured and the surface energy balance modelled from that perspective. Social and physical features of the city we identified in detail with the help of satellite images, GIS and 3D models. We determined the links between urban heat/surface energy balance and the social/physical features of Rotterdam by multivariable regression analysis. The crucial elements of the heat problem were then clustered and illustrated on a social and a physical heat map. RESULTS The research project produced two heat maps, an atlas of underlying data and a set of adaptation measures which, when combined, will make the city of Rotterdam and its inhabitants more aware and less vulnerable to heat wave-related health effects. CONCLUSION In different ways, the pre-war districts of the city (North, South, and West) are warmer and more vulnerable to urban heat than are other areas of Rotterdam. The temperature readings that we carried out confirm these findings as far as outdoor temperatures are concerned. Indoor temperatures vary widely. Homes seem to have their particular dynamics, in which the house’s age plays a role. The above-average mortality of those aged 75 and over during the July 2006 heat wave in Rotterdam can be explained by a) the concentration of people in this age group, b) the age of the homes they live in, and c) the sum of sensible heat and ground heat flux. A diverse mix of impervious surfaces, surface water, foliage, building envelopes and shade make one area or district warmer than another. Adaptation measures are in the hands of residents, homeowners and the local council alike, and relate to changing behaviour, physical measures for homes, and urban design respectively.

scholarly journals Study of Urban Heat Islands Using Different Urban Canopy Models and Identification Methods

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 521
Author(s):  
Rui Silva ◽  
Ana Cristina Carvalho ◽  
David Carvalho ◽  
Alfredo Rocha
Keyword(s):  
Land Use ◽  
Temperature Difference ◽  
Model Simulation ◽  
Urban Canopy ◽  
Near Surface ◽  
Local Method ◽  
Identification Methods ◽  
Classic Method ◽  
Urban Heat ◽  
The City

This work aims to compare the performance of the single‑(SLUCM) and multilayer (BEP-Building effect parameterization) urban canopy models (UCMs) coupled with the Weather Research and Forecasting model (WRF), along with the application of two urban heat island (UHI) identification methods. The identification methods are: (1) the “classic method”, based on the temperature difference between urban and rural areas; (2) the “local method” based on the temperature difference at each urban location when the model land use is considered urban, and when it is replaced by the dominant rural land use category of the urban surroundings. The study is performed as a case study for the city of Lisbon, Portugal, during the record-breaking August 2003 heatwave event. Two main differences were found in the UHI intensity (UHII) and spatial distribution between the identification methods: a reduction by half in the UHII during nighttime when using the local method; and a dipole signal in the daytime and nighttime UHI spatial pattern when using the classic method, associated with the sheltering effect provided by the high topography in the northern part of the city, that reduces the advective cooling in the lower areas under prevalent northern wind conditions. These results highlight the importance of using the local method in UHI modeling studies to fully isolate urban canopy and regional geographic contributions to the UHII and distribution. Considerable improvements were obtained in the near‑surface temperature representation by coupling WRF with the UCMs but better with SLUCM. The nighttime UHII over the most densely urbanized areas is lower in BEP, which can be linked to its larger nocturnal turbulent kinetic energy (TKE) near the surface and negative sensible heat (SH) fluxes. The latter may be associated with the lower surface skin temperature found in BEP, possibly owing to larger turbulent SH fluxes near the surface. Due to its higher urban TKE, BEP significantly overestimates the planetary boundary layer height compared with SLUCM and observations from soundings. The comparison with a previous study for the city of Lisbon shows that BEP model simulation results heavily rely on the number and distribution of vertical levels within the urban canopy.

scholarly journals Response of Urban Heat Stress to Heat Waves in Athens (1960–2017)

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 483 ◽  
Author(s):  
George Katavoutas ◽  
Dimitra Founda
Keyword(s):  
Heat Stress ◽  
Thermal Stress ◽  
Heat Wave ◽  
Heat Waves ◽  
Hot Spot ◽  
Urban Environments ◽  
Stress Conditions ◽  
Stress Levels ◽  
Urban Heat ◽  
Urban Sites

The increasing frequency, intensity and duration of heat waves seem to follow the observed global warming in recent decades. Vulnerability to heat waves is expected to increase in urban environments mainly due to population density and the effect of the urban heat island that make cities hotter than surrounding non-urban areas. The present study focuses on a vulnerable area of the eastern Mediterranean, already characterized as a ‘hot spot’ with respect to heat-related risk and investigates the change in heat stress levels during heat wave compared to non-heat wave conditions as well as the way that heat stress levels respond to heat waves in urban, compared to non-urban, environments. The adoption of a metric accounting for both the intensity and duration of the hot event yielded a total of 46 heat wave episodes over a nearly 60-year period, but with very rare occurrence until the late 1990s and a profound increased frequency thereafter. The results reveal a difference of at least one thermal stress category between heat wave and non-heat wave periods, which is apparent across the entire range of the thermal stress distribution. The analysis demonstrates a robust intensification of nighttime heat stress conditions in urban, compared to non-urban, sites during severe heat waves. Nevertheless, severe heat waves almost equalize heat stress conditions between urban and non-urban sites during midday.

scholarly journals Observation of the Urban Wind Island Effect

2020 ◽  
Vol 237 ◽  
pp. 06009
Author(s):  
Sunil Baidar ◽  
Tim Bonin ◽  
Aditya Choukulkar ◽  
Alan Brewer ◽  
Mike Hardesty
Keyword(s):  
Boundary Layer ◽  
Rural Areas ◽  
Wind Profile ◽  
Urban Canopy ◽  
Atmospheric Conditions ◽  
Canopy Layer ◽  
Wind Speeds ◽  
Island Effect ◽  
Urban Heat ◽  
The City

Urban wind island effect (UWI) is defined as a phenomenon in which boundary layer mean wind speeds in an urban area are noticeably higher than its neighboring rural areas. Unlike urban heat island effect which has been extensively studied, the UWI was only recently observed in a modeling study. Here we study existence of the UWI over Indianapolis, Indiana using wind profile measurements from two Doppler wind lidars (DWL) that were deployed in climatologically upwind and downwind of the city. Under certain atmospheric conditions higher wind speeds and turbulence were observed at the downwind site over the entire urban boundary layer outside the urban canopy layer.

A New Modeling Approach to Forecast Building Energy Demands During Extreme Heat Events in Complex Cities

2011 ◽  
Author(s):  
Estatio Gutie´rrez ◽  
Jorge E. Gonza´lez ◽  
Robert Bornstein ◽  
Mark Arend ◽  
Alberto Martilli
Keyword(s):  
Urban Heat Island ◽  
Heat Wave ◽  
Extreme Event ◽  
Large City ◽  
Urban Canopy ◽  
Anthropogenic Heat ◽  
Heat Island ◽  
Urban Canopy Model ◽  
Urban Heat ◽  
Canopy Model

The thermal response of a large city including the energy production aspects of it are explored for a large and complex city using urbanized atmospheric mesoscale modeling. The Weather Research and Forecasting (WRF) mesocale model is coupled to a multi-layer urban canopy model that considers thermal and mechanical effects of the urban environment including a building scale energy model to account for anthropogenic heat contributions due to indoor-outdoor temperature differences. This new urban parameterization is used to evaluate the evolution and the resulting urban heat island formation associated to a 3-day heat wave in New York City (NYC) during the summer of 2010. High resolution (250 m.) urban canopy parameters (UCPs) from the National Urban Database were employed to initialize the multi-layer urban parameterization. The precision of the numerical simulations is evaluated using a range of observations. Data from a dense network of surface weather stations, wind profilers and Lidar measurements are compared to model outputs over Manhattan and its surroundings during the 3-days event. The thermal and drag effects of buildings represented in the multilayer urban canopy model improves simulations over urban regions giving better estimates of the surface temperature and wind speed. An accurate representation of the nocturnal urban heat island registered over NYC in the event was obtained from the improved model. The accuracy of the simulation is further assessed against more simplified urban parameterizations models with positive results with new approach. Results are further used to quantify the energy consumption of the buildings during the heat wave, and to explore alternatives to mitigate the intensity of the UHI during the extreme event.

scholarly journals Evaluating three urban canopy models against in-situ observations for a heat-wave case in Amsterdam

2021 ◽  
Author(s):  
Arjan Willemse ◽  
Alberto Martilli ◽  
Bert Heusinkveld ◽  
Oscar Hartogensis ◽  
Gert-Jan Steeneveld
Keyword(s):  
Heat Wave ◽  
Air Temperature ◽  
Air Conditioning ◽  
Urban Canopy ◽  
City Center ◽  
Near Surface ◽  
Current Climate ◽  
The Future ◽  
The City

<p>With increasing urbanization and ongoing climate change there is a need to develop and evaluate modelling infrastructure for urban weather and climate. In this study we evaluate three urban canopy models for a heat-wave case study in Amsterdam (The Netherlands), notably the single-layer urban canopy model (SLUCM) and the building environment parameterization (BEP) and the BEP+BEM (BEP+Building Energy model) urban canopy models within the WRF infrastructure. Model results are evaluated against a network of near surface observations of air temperature, turbulent surface fluxes, SODAR wind profiles, and radio soundings of temperature and humidity taken in the city center of Amsterdam.</p><p>We find that the BEP+BEM model outperforms the other schemes for the near surface air temperature, with a bias of -0.66 K for BEP+BEM, -1.51 K for BEP and-1.56 K for SLUCM. However, WRF produces an elevated inversion level that, at the same time, is substantially (~ 2-8 K) weaker than observed in the radiosoundings.</p><p>To estimate the future increase in energy demand by air conditioning, we project this heatwave case study to the future. To do so, we force the WRF model with increased temperatures in initial and boundary conditions following the four KNMI climate scenarios. With the climate scenario with the largest warming (WH-scenario) we find a 2-m temperature increase of ~3 K during daytime compared to the current climate. Finally we find that for this scenario the energy consumption by air-conditioning increases between 25% and 40% in the city center compared to the current climate (with constant number of airco’s installed).</p>

scholarly journals Explore the Accuracy of the Pedestrian Level Temperature Estimated by the Combination of LCZ with WRF Urban Canopy Model through the Microclimate Measurement Network

2021 ◽  
Vol 8 (1) ◽  
pp. 14
Author(s):  
Yu-Cheng Chen ◽  
Fang-Yi Cheng ◽  
Cheng-Pei Yang ◽  
Tzu-Ping Lin
Keyword(s):  
Heat Capacity ◽  
Urban Development ◽  
Urban Climate ◽  
Urban Canopy ◽  
Subtropical Climate ◽  
Heat Island ◽  
Urban Canopy Model ◽  
Urban Heat ◽  
The City ◽  
Canopy Model

Due to the urban heat island effect becoming more evident in the cities in Taiwan, the urban climate has become an essential factor in urban development. Taiwan is located on the border of tropical and subtropical climate zones, the climate condition is hot and humid, and the city shows high-density development. The dense urban development has increased the heat storage capacity of the ground and buildings. However, if only the climate stations set by the Central Meteorological Bureau to observe the climate data are applied, the predicted results differ from the actual urban climate conditions due to the small number of these stations and the too far distance between them. Therefore, this study employs the local climate zone (LCZ), which can classify the land features by considering both land use and land cover, and can be freely generated from satellite images. The LCZ classification method can view the type of the city through the height and density of obstacles. This study also combines the urban canopy model (UCM) of the mesoscale climate prediction model and weather research and forecasts (WRF). This approach can calculate vertical and horizontal planes of the city, such as building volume, road width, the influence of streets and roofs, roof heat capacity, building wall heat capacity, etc., to predict the climatic conditions in different lands in the study area. Simultaneously, to understand the actual distribution of urban climate more accurately, this study used the microclimate measurement network built in the research area to produce pedestrian-level temperature distribution and compared the estimated results with the actual measured values for urban climate assessment. This study can understand the cause of urban heat islands and assist urban planners more appropriately formulate heat island mitigation strategies in different regions.

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