The air pollution situation in the German city of Stuttgart is very important, as high pollutant concentrations are measured here compared to other German cities. This is mainly due to Stuttgart’s ...geographical location as it is in a basin covered by hills on three sides. This leads to reduced wind speeds that inhibit pollutant dispersion. One of the main contributors to the pollutant concentrations in Stuttgart is local traffic. To improve the air quality in Stuttgart, a diesel traffic ban was introduced on 1 January 2019, and is ongoing. In this study, the urban climate model PALM-4U was applied to obtain the pollutant distribution along the federal highways B14 and B27 of Stuttgart to evaluate the impact of the diesel traffic ban on air quality. The simulations were carried out in two areas of the city, namely the city center and Kaltental Valley, with domain sizes of 3.2 km × 2 km and 3.2 km × 1.6 km, respectively, and with a grid size of 10 m for each domain. The influence of traffic emissions on the air quality of Stuttgart was studied for a typical summer day. The results showed that air pollutant concentrations were highest near federal highways B14 and B27 (e.g., NO2 concentration peaks of around 200 µg/m3). Also, a significant reduction of around four times in air pollutant concentrations was observed in the study area after the diesel traffic ban was introduced.
The use and promotion of green infrastructure (GI) is of great importance for improving urban climates and for helping cities to be more resilient and sustainable in the context of climate change. ...For this reason, the effect of urban parks on city climates is of great interest for research. In this study, temperature measurements were made during 14 nights in the winter and spring of 2015 in the largest park of the Mediterranean city of Barcelona, Spain: the Ciutadella Park. The analysis of the measurements made inside the park and in its adjacent urban environment has confirmed the existence of an urban cool island (UCI) with a maximum cooling intensity of 5.2°C (9.4°F) in winter, under anticyclonic situations preferably, and an average cooling intensity of 2.7°C (4.9°F). In the spring months, the urban cool island has an intensity under the average, with a maximum of 2.1°C (3.8°F).
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•We quantified the relationship between urban forms and thermal comfort.•Our CFD and thermal comfort models were validated by measurements.•Our coupled model produced comparable Tmrt ...and sensible PET relative to other studies.•Predicted PETs at noon were more than 10 °C relative to the morning within buildings.•Modifications of building lengths and porosity were keys to reduce heat stresses.
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.
•Existing knowledge on outdoor mist cooling was first-time systematically reviewed.•The potential for comfort enhancement and energy saving was comparatively assessed.•Climate sensitivity, ...technological options and driving forces were discussed.•Numerical and experimental methodologies were critically analyzed.•Design guidelines were inferred by merging dominant trends and results.
For the first time, a systematic review was conducted on mist spraying systems used for outdoor cooling by perusing twenty years of publications from 12 countries and 7 climatic zones. The twofold aim was to emphasize both the potential against local overheating in a variety of climatic contexts and the extreme heterogeneity in terms of investigation techniques and performance metrics that hinder the construction of a cohesive body of knowledge. In addition to statistics and patterns, data were screened to outline theoretical and methodological trends and gaps and to detect geographic biases and climate dependencies. Indeed, each study was thoroughly described and comparatively discussed according to (i) the investigational method (purely experimental studies, purely numerical studies and those combining field tests with simulations), (ii) the results in terms of cooling, humidification and comfort, also in relation to the adopted performance metrics (iii) the design novelty. Most relevant approaches and findings were discussed and compared to identify governing variables, optimized configurations, unchartered solutions and criticalities. Overall, the collected data qualify water spraying as a cost-effective, versatile and high-impact blue mitigator. Opportunities and challenges towards an informed use emerged and will help delineating appropriate guidelines for practitioners involved in town development, to deliver strategies and precautions.
This paper presents a novel study on the multi-objective energy audit and management of a proposed plus-ZEB covered by a green roof in Tehran’s climate. The planning impact of changing a proposed ...plus-ZEB to an intensive plus-ZEB is also evaluated. The planning is performed for one year based on Tehran’s accurate urban climate data. The plus-ZEB consists of renewable and non-renewable resources like CHP, boiler, furnace, photovoltaic, solar water heater, wind turbine, air to the water heat pump, electric heat pump, and chiller boiler units in addition to energy storage to supply diverse electrical, thermal, and cooling demands of the presented building. The planning’s functions are included in the total cost and emission of the plus-ZEB. The objective function prioritization is also participated to show the planner’s decision on the function. Also, diverse solvers are implemented to evaluate and compare and validate results. The problem is simulated in energy plus to assess the amount of demands, construction materials, and energy audit issues; then, the results transfer to the GAMS software for energy management of the proposed plus-ZEB by utilizing a green roof. The problem in GAMS is modeled as a real mixed-integer programming (RMIP) and solved using the augmented epsilon constraint method (AEC). The final results show the significant effect of the proposed planning on reducing the cost and emission of the plus-ZEB, in which the total cost and pollution are decreased by about 7.4 % and 10.6 %, respectively.
This open access book presents a catalogue of over one thousand indicators which can be used by cities' public administrators to monitor and evaluate social innovation action plans to support ...people-centred, collaborative or co-designed solutions to lower carbon emissions. Indicators are clustered according to a framework of social innovation solutions for climate neutrality at city level, developed by merging top-down academic knowledge with bottom-up pragmatic case studies. There is currently limited guidance on how to embed social innovations in their cities’ action plans with the aim of reaching climate neutrality, and on how to assess the progress and impacts of such people-centred projects in cities. The book addresses this gap and is thus relevant for scholars in the field of policy-making and design, as well as cities’ transition teams, policymakers and consultants. Based on the work developed within the EU-funded project NetZeroCities, intervention logics are provided for each of the ten categories of action, with related indicators clustered by category and evaluation criteria (effectiveness, efficiency, relevance, replicability, and scalability). Guidelines to implement the framework support city administrators in defining steps they need to follow to apply the indicators to their local case, making social innovation a crucial lever for accelerating systemic transformation.
The Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is one of the regions with the fastest urbanization process in China in the past 4 decades. The urbanization process of the GBA is still ongoing ...and the meteorological observation resource in the region is rich, making the GBA an ideal testbed for the study of urban climate. In the past decades, the studies on the urban climate in the GBA has been quite active. The topics of these studies can be categorized into 3 topics: (1) urban climate characteristics and variations in the GBA, including significant increase in average temperature, decrease in relative humidity and average wind speed, and more frequent extreme precipitation; (2) challenges brought by urban climate change to GBA, such as the meteorological conditions affecting the atmospheric environment have become more complex, the health risk of urban residents has increased, the risk of urban flash flood and waterlogging has increased, and the demand for urban energy consumption has also increased significantly; (3) technologies and strategies to mitigate and adapt to urban climate change in GBA, including the optimization of urban wind environment, the regulation of urban thermal environment and the response technology of urban flood disaster.
•Urbanization made Guangdong-Hong Kong-Macau Greater Bay Area (GBA) hotter, drier and increased the intensity of rainstorms.•Challenges induced by climate change in GBA are in environment, health, public safety and energy.•Urban climate researches help GBA to adapt to climate change.
If we are to achieve climate change targets, transport systems need to transform. This article is concerned with the prospects of challenging the regime of automobility in urban areas. It employs a ...governmentality framework, alongside theories of automobility, in order to analyse mobility governmentalities in Gothenburg, Sweden. Gothenburg is an interesting case in the context of reducing car use given its identity as a ‘car city.’ Despite this, Gothenburg has high ambitions in terms of reducing car traffic. Reaching these goals are however associated with challenges: prognoses predict a continued increase in car traffic, and political acceptance is viewed as an obstacle. The article’s findings are based on semi-structured interviews with public officials and stakeholders, zooming in on (1) conflicting spatialities and temporalities (2) competing logics of circulation and pace and (3) mobility imaginaries of the (im)possible. We argue that while there are new logics entering urban mobility governmentalities as an effect of the climate transition, their possibilities to affect material change are confined because the movement and circulation of ‘people and things,’ ultimately represented by the private car, are closely tied to the way that freedom is exercised, understood and manifested in contemporary liberal societies.
Urban trees ameliorate heat stress for urban dwellers. However, it is difficult to quantitatively assess the integrated impacts of tree planting and street layouts on visual and thermal comfort in ...simulations and urban field experiments. We conducted scaled outdoor experiments in Guangzhou to investigate the influence of tree plantings on pedestrian visual and thermal comfort in street canyons with various aspect ratios (H/W = 1, 2, 3; H = 1.2 m). We considered the effects of tree crown covers (big and small crown) and tree planting densities (ρ = 1, 0.5) on pedestrian illuminance level and two thermal comfort indices (Physiological Equivalent Temperature: PET and Index of Thermal Stress: ITS).
When ρ = 1, trees in most cases reduce pedestrian illuminance (maximum 140.0klux) and improve visual comfort. Decreasing ρ from 1 to 0.5 increases the illuminance (maximum 179.5klux) in the streets with big crown trees (H/W = 1, 2) and in the street with small crown trees (H/W = 2). When ρ = 1 (H/W = 1, 2), big crown trees decrease the peak daytime PET (by about 4.0 °C) and ITS (by about 285 W). Small crown trees (ρ = 1, H/W = 1, 2) produce a warming effect on peak daytime PET (2.0-3.0 °C), but a reduction in ITS is observed when H/W = 2, 3. After reducing ρ from 1 to 0.5, big crown trees increase peak daytime thermal stress according to both indices when H/W = 1, 2. Small crown trees exhibit a similar PET cycle between ρ = 0.5 and ρ = 1 across various H/W, but their daytime reduction of ITS is less effective when ρ = 0.5 (H/W = 2). The discrepancies between PET and ITS are attributed to their different approaches to modelling radiation fluxes. The narrower the street, the lower the illuminance, PET, and ITS, while their increases caused by reduced ρ are limited in narrow streets. Our study informs some potential urban tree planting strategies and produces high-quality validation data for numerical simulations and theoretical models.
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•Scaled outdoor experiments are tested for tree impacts in streets (H/W = 1–3, H = 1.2 m).•Tree plantings reduce pedestrian illuminance by up to 140 klux.•Big crown trees reduce daytime PET (4.0 °C) and ITS (285 W) to improve thermal comfort.•Big crown trees increase PET and ITS as planting density reduces (ρ = 1 to ρ = 0.5).•During daytime, small crown trees reduce ITS but increase PET.
Paucity of information on Urban Canopy Parameters (UCPs) is considered as one of the major reason behind limited urban climate research and modelling in developing region of Asia, Africa, and Latin ...America. UCPs define those characteristics of urban built form which have direct or indirect influence on urban climate. Most of the studies in developed world have utilized 3-Dimension (3D) Geographic Information System (GIS) database either developed from ground survey or Remotely Sensed (RS) data such as Aerial Photographs, Airborne Light Detection and Ranging (LiDAR) and high-resolution Interferometric Synthetic Aperture Radar (InSAR) data for retrieval of UCPs. However, non-existence of 3D GIS database and limited availability of above RS datasets in developing region necessitates to employ widely available low-cost alternative datasets for retrieval of UCPs. Hence, this study focuses on retrieval of UCPs by employing Very High Resolution Satellite (VHRS) optical stereo data, which has repeat availability, low cost and extensive coverage, in a highly dense and complex urban environment with a challenging composite climate like Delhi, India. A novel methodology for extraction of gridded UCPs from VHRS optical stereo data has been developed in this study to overcome the limitation of extraction of individual building footprint in dense and compact urban built-up. The validation of key UCPs such as building height (Mean error, Root Mean Square Error (RMSE) and Mean Absolute Error <1 m in all height groups), Building Surface Area (Accuracy 84.27%) and Sky View Factor (RMSE = 0.046 and correlation = 0.94) with ground measurements has displayed reasonable accuracies. Hence, the study demonstrates successfully the use of VHRS optical satellite stereo data for generation of gridded UCPs in a highly heterogeneous and dense urban built-up environment. The developed approach is globally replicable in any city of any country.
