Numerical simulation of urban thermal plume merging

<p>Densely packed urban buildings trap outgoing long-wave radiation, leading to reduced surface cooling and increased building surface temperature. In calm conditions, poor natural ventilation causes both thermal comfort and air quality issue. The buoyancy flow generated by heated urban surfaces is the main driving of the urban flow and pollutant dispersion. A 3D numerical modelling is conducted to investigate the thermal plumes merging and buoyancy-driven airflow in urban areas. The performances of four different turbulence models, i.e., two URANS (Unsteady Reynolds-averaged Navier&#8211;Stokes equations) models and two LES (Large-Eddy Simulation) models are evaluated by comparing the velocity field with previous water tank measurements. Validation results show that all four turbulence models can capture the bending of thermal plumes toward the centre, and LES models provide a better prediction on the vertical velocity profiles, while both URANS models show underestimation. The plume merging mechanism is analysed with the high accuracy LES results. Both pressure difference and swaying motion caused by mean flow and turbulence are important for plume merging. The turbulence coherent structure of plume merging is analysed by a quadrant analysis, which shows ejection and sweep events could significantly change with the building density. A case study with complex urban geometry is conducted to show the impact of thermal plumes merging in the real high-density urban areas. The convergence airflow at the pedestrian level is estimated to 2 m/s under a surface-air temperature difference of 5 &#176;C, which is comparable to wind-driven ventilation and beneficial to thermal comfort and air quality.</p>

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Modelling the impact of megacities on local, regional and global tropospheric ozone and the deposition of nitrogen species

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-12215-2013 ◽

2013 ◽

Vol 13 (24) ◽

pp. 12215-12231 ◽

Cited By ~ 14

Author(s):

Z. S. Stock ◽

M. R. Russo ◽

T. M. Butler ◽

A. T. Archibald ◽

M. G. Lawrence ◽

...

Keyword(s):

Air Quality ◽

Urban Areas ◽

Climate Model ◽

Surface Ozone ◽

Global Scale ◽

Chemical Environment ◽

Ozone Production ◽

The Uk ◽

The Impact ◽

Local Emissions

Abstract. We examine the effects of ozone precursor emissions from megacities on present-day air quality using the global chemistry–climate model UM-UKCA (UK Met Office Unified Model coupled to the UK Chemistry and Aerosols model). The sensitivity of megacity and regional ozone to local emissions, both from within the megacity and from surrounding regions, is important for determining air quality across many scales, which in turn is key for reducing human exposure to high levels of pollutants. We use two methods, perturbation and tagging, to quantify the impact of megacity emissions on global ozone. We also completely redistribute the anthropogenic emissions from megacities, to compare changes in local air quality going from centralised, densely populated megacities to decentralised, lower density urban areas. Focus is placed not only on how changes to megacity emissions affect regional and global NOx and O3, but also on changes to NOy deposition and to local chemical environments which are perturbed by the emission changes. The perturbation and tagging methods show broadly similar megacity impacts on total ozone, with the perturbation method underestimating the contribution partially because it perturbs the background chemical environment. The total redistribution of megacity emissions locally shifts the chemical environment towards more NOx-limited conditions in the megacities, which is more conducive to ozone production, and monthly mean surface ozone is found to increase up to 30% in megacities, depending on latitude and season. However, the displacement of emissions has little effect on the global annual ozone burden (0.12% change). Globally, megacity emissions are shown to contribute ~3% of total NOy deposition. The changes in O3, NOx and NOy deposition described here are useful for quantifying megacity impacts and for understanding the sensitivity of megacity regions to local emissions. The small global effects of the 100% redistribution carried out in this study suggest that the distribution of emissions on the local scale is unlikely to have large implications for chemistry–climate processes on the global scale.

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Emission of fine particles (PM2.5) from residential biomass combustion in Croatia and how to reduce it

Environmental engineering ◽

10.37023/ee.7.2.6 ◽

2020 ◽

Vol 7 (2) ◽

pp. 84-94

Author(s):

Mirela Poljanac

Keyword(s):

Air Quality ◽

Human Health ◽

Urban Areas ◽

Fine Particles ◽

Biomass Combustion ◽

Rural And Urban Areas ◽

Wood Burning ◽

Rural And Urban ◽

The Impact ◽

Pm2.5 Emissions

Wood burning in residential appliances is very represented in the Republic of Croatia. It is a main or an additional form of heating for many households in rural and urban areas and is therefore an important source of air pollution. The choice of energy and the combustion appliance used in home have a significant impact on PM2.5 emissions. The paper informs the reader about PM2.5 emissions, their main sources and impacts on human health, environment, climate, air quality, and the reason why PM2.5 emissions from residential wood burning are harmful. Paper also gives an overview of spatial PM2.5 emission distribution in Croatia, their five air quality zones and four agglomerations. The paper analyses the sources and their contribution to PM2.5 emissions with the relevance of PM2.5 emissions from residential plants, the use of fuels in residential plants and their contribution to PM2.5 emissions and PM2.5 emissions by fuel combustion technologies in residential sector. Appropriate strategies, policies, and actions to reduce the impact of residential biomass (wood) burning on the environment, air quality and human health are considered.

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Impacts of Current and Projected Oil Palm Plantation Expansion on Air Quality Over Southeast Asia

10.5194/acp-2016-158 ◽

2016 ◽

Author(s):

Sam J. Silva ◽

Colette L. Heald ◽

Jeffrey A. Geddes ◽

Kemen G. Austin ◽

Prasad S. Kasibhatla ◽

...

Keyword(s):

Air Quality ◽

Southeast Asia ◽

Oil Palm ◽

Urban Areas ◽

Transport Model ◽

Chemical Transport Model ◽

Oil Palm Plantation ◽

Deposition Velocities ◽

Current Constellation ◽

The Impact

Abstract. Over recent decades oil palm plantations have rapidly expanded across Southeast Asia (SEA). According to the United Nations, oil palm production in SEA increased by a factor of 3 from 1995 to 2010. We investigate the impacts of current (2010) and future (2020) oil palm expansion in SEA on surface-atmosphere exchange and the resulting air quality in the region. For this purpose, we use satellite data, high-resolution land maps, and the chemical transport model GEOS-Chem. Relative to a no oil palm plantation scenario (~ 1990), overall simulated isoprene emissions in the region increase by 13 % due to oil palm plantations in 2010 and a further 11 % by 2020. In addition, the expansion of palm plantations leads to local increases in ozone deposition velocities of up to 20 %. The net result of these changes is that oil palm expansion in SEA increases surface O3 by up to 3.5 ppbv over dense urban regions, and could rise more than 4.5 ppbv above baseline levels by 2020. Biogenic secondary organic aerosol loadings also increase by up to 1 μg m−3 due to oil palm expansion, and could increase a further 2.5 μg m−3 by 2020. Our analysis indicates that while the impact of recent oil palm expansion on air quality in the region has been significant, the retrieval error and sensitivity of the current constellation of satellite measurements limit our ability to observe these impacts from space. Oil palm expansion is likely to continue to degrade air quality in the region in the coming decade and hinder efforts to achieve air quality regulations in major urban areas such as Kuala Lumpur and Singapore.

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Urban Trees and Their Impact on Local Ozone Concentration—A Microclimate Modeling Study

Atmosphere ◽

10.3390/atmos10030154 ◽

2019 ◽

Vol 10 (3) ◽

pp. 154 ◽

Cited By ~ 7

Author(s):

Helge Simon ◽

Joachim Fallmann ◽

Tim Kropp ◽

Holger Tost ◽

Michael Bruse

Keyword(s):

Air Quality ◽

Urban Planning ◽

Ozone Concentration ◽

Green Infrastructure ◽

Urban Areas ◽

Urban Trees ◽

Box Model ◽

Dominant Factor ◽

Isoprene Emission ◽

The Impact

Climate sensitive urban planning involves the implementation of green infrastructure as one measure to mitigate excessive heat in urban areas. Depending on thermal conditions, certain trees tend to emit more biogenic volatile organic compounds, which act as precursors for ozone formation, thus hampering air quality. Combining a theoretical approach from a box model analysis and microscale modeling from the microclimate model ENVI-met, we analyze this relationship for a selected region in Germany and provide the link to air quality prediction and climate sensitive urban planning. A box model study was conducted, indicating higher ozone levels with higher isoprene concentration, especially in NO-saturated atmospheres. ENVI-met sensitivity studies showed that different urban layouts strongly determine local isoprene emissions of vegetation, with leaf temperature, rather than photosynthetic active radiation, being the dominant factor. The impact of isoprene emission on the ozone in complex urban environments was simulated for an urban area for a hot summer day with and without isoprene. A large isoprene-induced relative ozone increase was found over the whole model area. On selected hot spots we find a clear relationship between urban layout, proximity to NOx emitters, tree-species-dependent isoprene emission capacity, and increases in ozone concentration, rising up to 500% locally.

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Changes in regional meteorology induced by anthropogenic heat and their impacts on air quality in South China

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-15011-2016 ◽

2016 ◽

Vol 16 (23) ◽

pp. 15011-15031 ◽

Cited By ~ 20

Author(s):

Min Xie ◽

Kuanguang Zhu ◽

Tijian Wang ◽

Wen Feng ◽

Da Gao ◽

...

Keyword(s):

Air Quality ◽

Wind Speed ◽

South China ◽

Urban Areas ◽

Air Pollutants ◽

Surface Wind ◽

Vertical Movement ◽

Anthropogenic Heat ◽

Big Cities ◽

The Impact

Abstract. Anthropogenic heat (AH) emissions from human activities can change the urban circulation and thereby affect the air pollution in and around cities. Based on statistic data, the spatial distribution of AH flux in South China is estimated. With the aid of the Weather Research and Forecasting model coupled with Chemistry (WRF/Chem), in which the AH parameterization is developed to incorporate the gridded AH emissions with temporal variation, simulations for January and July in 2014 are performed over South China. By analyzing the differences between the simulations with and without adding AH, the impact of AH on regional meteorology and air quality is quantified. The results show that the regional annual mean AH fluxes over South China are only 0.87 W m−2, but the values for the urban areas of the Pearl River Delta (PRD) region can be close to 60 W m−2. These AH emissions can significantly change the urban heat island and urban-breeze circulations in big cities. In the PRD city cluster, 2 m air temperature rises by 1.1° in January and over 0.5° in July, the planetary boundary layer height (PBLH) increases by 120 m in January and 90 m in July, 10 m wind speed is intensified to over 0.35 m s−1 in January and 0.3 m s−1 in July, and accumulative precipitation is enhanced by 20–40 % in July. These changes in meteorological conditions can significantly impact the spatial and vertical distributions of air pollutants. Due to the increases in PBLH, surface wind speed and upward vertical movement, the concentrations of primary air pollutants decrease near the surface and increase in the upper levels. But the vertical changes in O3 concentrations show the different patterns in different seasons. The surface O3 concentrations in big cities increase with maximum values of over 2.5 ppb in January, while O3 is reduced at the lower layers and increases at the upper layers above some megacities in July. This phenomenon can be attributed to the fact that chemical effects can play a significant role in O3 changes over South China in winter, while the vertical movement can be the dominant effect in some big cities in summer. Adding the gridded AH emissions can better describe the heterogeneous impacts of AH on regional meteorology and air quality, suggesting that more studies on AH should be carried out in climate and air quality assessments.

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The impact of ship emissions on air quality and human health in the Gothenburg area – Part II: Scenarios for 2040

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-10667-2020 ◽

2020 ◽

Vol 20 (17) ◽

pp. 10667-10686

Author(s):

Martin O. P. Ramacher ◽

Lin Tang ◽

Jana Moldanová ◽

Volker Matthias ◽

Matthias Karl ◽

...

Keyword(s):

Air Quality ◽

Health Effects ◽

Urban Areas ◽

Large Scale ◽

Health Effect ◽

Population Exposure ◽

Future Scenarios ◽

Port Area ◽

The Future ◽

The Impact

Abstract. Shipping is an important source of air pollutants, from the global to the local scale. Ships emit substantial amounts of sulfur dioxides, nitrogen dioxides, and particulate matter in the vicinity of coasts, threatening the health of the coastal population, especially in harbour cities. Reductions in emissions due to shipping have been targeted by several regulations. Nevertheless, effects of these regulations come into force with temporal delays, global ship traffic is expected to grow in the future, and other land-based anthropogenic emissions might decrease. Thus, it is necessary to investigate combined impacts to identify the impact of shipping activities on air quality, population exposure, and health effects in the future. We investigated the future effect of shipping emissions on air quality and related health effects considering different scenarios of the development of shipping under current regional trends of economic growth and already decided regulations in the Gothenburg urban area in 2040. Additionally, we investigated the impact of a large-scale implementation of shore electricity in the Port of Gothenburg. For this purpose, we established a one-way nested chemistry transport modelling (CTM) system from the global to the urban scale, to calculate pollutant concentrations, population-weighted concentrations, and health effects related to NO2, PM2.5, and O3. The simulated concentrations of NO2 and PM2.5 in future scenarios for the year 2040 are in general very low with up to 4 ppb for NO2 and up to 3.5 µg m−3 PM2.5 in the urban areas which are not close to the port area. From 2012 the simulated overall exposure to PM2.5 decreased by approximately 30 % in simulated future scenarios; for NO2 the decrease was over 60 %. The simulated concentrations of O3 increased from the year 2012 to 2040 by about 20 %. In general, the contributions of local shipping emissions in 2040 focus on the harbour area but to some extent also influence the rest of the city domain. The simulated impact of onshore electricity implementation for shipping in 2040 shows reductions for NO2 in the port of up to 30 %, while increasing O3 of up to 3 %. Implementation of onshore electricity for ships at berth leads to additional local reduction potentials of up to 3 % for PM2.5 and 12 % for SO2 in the port area. All future scenarios show substantial decreases in population-weighted exposure and health-effect impacts.

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The impact of ship emissions on air quality and human health in the Gothenburg area – Part II: Scenarios for 2040

10.5194/acp-2020-319 ◽

2020 ◽

Cited By ~ 1

Author(s):

Martin O. P. Ramacher ◽

Lin Tang ◽

Jana Moldanová ◽

Volker Matthias ◽

Matthias Karl ◽

...

Keyword(s):

Air Quality ◽

Health Effects ◽

Urban Areas ◽

Large Scale ◽

Health Effect ◽

Population Exposure ◽

Future Scenarios ◽

Port Area ◽

The Future ◽

The Impact

Abstract. Shipping is an important source of air pollutants, from the global to the local scale. Ships are emitting substantial amounts of sulphur dioxides, nitrogen dioxides and particulate matter in the vicinity of coasts, threatening the health of the coastal population, especially in harbour cities. Reductions of emissions due to shipping have been targeted by several regulations. Nevertheless, effects of these regulations come into force with temporal delays, global ship traffic is expected to grow in the future, and other land-based anthropogenic emissions might decrease. Thus, it is necessary to investigate combined impacts to identify the impact of shipping activities on air quality, population exposure and health-effects in the future. We investigated the future effect of shipping emissions on air quality and related health effects considering different scenarios of the development of shipping under current regional trends of economic growth and already decided regulations in the Gothenburg urban area in 2040. Additionally, we investigated the impact of a large-scale implementation of shore electricity in the port of Gothenburg. For this purpose, we established a one-way nested chemistry transport modelling (CTM) system from the global to the urban scale, to calculate pollutant concentrations, population weighted concentrations and health-effects related to NO2, PM2.5 and O3. The simulated concentrations of NO2 and PM2.5 in future scenarios for the year 2040 are in general very low with up to 4 ppb for NO2 and up to 3.5 µg/m3 PM2.5 in the urban areas which are not close to the port area. From 2012 the simulated overall exposure to PM2.5 decreased by approximately 30 % in simulated future scenarios, for NO2 the decrease was over 60 %. The simulated concentrations of O3 increased from year 2012 to 2040 by about 20 %. In general, the contributions of local shipping emissions in 2040 focus on the harbour area but to some extent also influence the rest of the city domain. The simulated impact of wide use of shore-site electricity for shipping in 2040 shows reductions for NO2 in the port with up to 30 %, while increasing O3 of up to 3 %. Implementation of on-shore electricity for ships at berth leads to additional local reduction potentials of up to 3 % for PM2.5 and 12 % for SO2 in the port area. All future scenarios show substantial decreases in population weighted exposure and health-effect impacts.

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Air Enthalpy as an IAQ Indicator in Hot and Humid Environment—Experimental Evaluation

Energies ◽

10.3390/en13061481 ◽

2020 ◽

Vol 13 (6) ◽

pp. 1481 ◽

Cited By ~ 1

Author(s):

Michał Piasecki ◽

Krystyna Kostyrko ◽

Małgorzata Fedorczak-Cisak ◽

Katarzyna Nowak

Keyword(s):

Air Quality ◽

Thermal Comfort ◽

Indoor Air Quality ◽

Indoor Air ◽

Test Chamber ◽

Indoor Environmental Quality ◽

Zero Energy Building ◽

Experimental Function ◽

Experimental Values ◽

The Impact

The authors studied the impact of indoor air humidity in the range of 60% to 90% on building user perception in the temperature range of 26 to 28 °C. The research thesis was put forward that the impact of humidity on indoor air quality dissatisfaction of building users in a warm and humid indoor environment is greater than that indicated in thermal comfort models. The presented experiment examined the indoor air quality perception of n = 28 subjects in the test chamber of a nearly zero energy building under ten environmental conditions, together with a thermal comfort assessment. The authors developed an experimental relation for predicting building users’ satisfaction based on the Weber–Fechner law, where the predicted percentage of dissatisfied users (PD) is determined by means of air enthalpy (h), PD = f(h). The obtained results confirmed the sated thesis. Additionally, the intersection points of the experimental function and isotherms resulting from the Fanger model are presented, where the thermal comfort assessment starts to indicate lower user dissatisfaction results than experimental values. The authors recommend the experimental equation for humid air enthalpies in the range of 50 to 90 kJ/kg. The indoor air quality assessment based on the enthalpy value is simple and can be used to determine the overall Indoor Environmental Quality index of a building (IEQindex).

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Air Quality Planning and the Minimization of Negative Externalities

Resources ◽

10.3390/resources8010015 ◽

2019 ◽

Vol 8 (1) ◽

pp. 15 ◽

Cited By ~ 2

Author(s):

Marco Ravina ◽

Deborah Panepinto ◽

Mariachiara Zanetti

Keyword(s):

Air Quality ◽

Urban Areas ◽

District Heating ◽

Heating System ◽

Negative Externalities ◽

District Heating System ◽

Quality Planning ◽

Air Quality Planning ◽

The Impact

The minimization of negative externalities is a key aspect in the development of a circular and sustainable economic model. At the local scale, especially in urban areas, externalities are generated by the adverse impacts of air pollution on human health. Local air quality policies and plans often lack of considerations and instruments for the quantification and evaluation of external health costs. Support for decision-makers is needed, in particular during the implementation stage of air quality plans. Modelling tools based on the impact pathway approach can provide such support. In this paper, the implementation of health impacts and externalities analysis in air quality planning is evaluated. The state of the art in European member states is reported, considering whether and how health effects have been included in the planning schemes. The air quality plan of the Piemonte region in Italy is then considered. A case study is analyzed to evaluate a plan action, i.e., the development of the district heating system in the city of Turin. The DIATI (Dipartimento di Ingegneria dell’Ambiente, del Territorio e delle Infrastrutture) Dispersion and Externalities Model (DIDEM model) is applied to detect the scenario with the highest external cost reduction. This methodology results are extensible and adaptable to other actions and measures, as well as other local policies in Europe. The use of health externalities should be encouraged and integrated into the present methodology supporting air quality planning. Efforts should be addressed to quantify and minimize the overall uncertainty of the process.

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Development, validation, and demonstration of the VTUF-3D v1.0 urban micro-climate model to support assessments of urban vegetation influences on human thermal comfort

10.31237/osf.io/d769f ◽

2018 ◽

Cited By ~ 1

Author(s):

Kerry Nice

Keyword(s):

Thermal Comfort ◽

Urban Environment ◽

Urban Areas ◽

Climate Model ◽

Canopy Cover ◽

Individual Tree ◽

New Model ◽

Human Thermal Comfort ◽

Physiological Processes ◽

The Impact

With urban areas facing future longer duration heat-waves and temperature extremes from climate change and growing urban development, adaptation strategies are needed. Examining the role that increased tree cover and water availability can have on human thermal comfort (HTC) in urban areas as part of these strategies has been done using observations, but further work requires a modelling tool suited for this task. Sufficient model resolution is needed to resolve variables used to calculate HTC, as well as the ability to model the physiological processes of vegetation and their interaction with water and with the rest of the urban environment. The lack of such a model has been identified as a research gap in the urban climate area and has impaired the ability to fully examine the use of urban greenery and water for improved human thermal comfort. A new model, VTUF-3D (Vegetated Temperatures Of Urban Facets), addresses this gap by embedding the functionality of the MAESPA tree process model (Duursma & Medlyn 2012), that can model individual trees, vegetation, and soil components, within the TUF-3D (Krayenhoff & Voogt 2007) urban micro-climate model. An innovative tiling approach, allows the new model to account for important vegetative physiological processes and shading effects using configurable templates to allow representation of any type of vegetation or water sensitive design feature. The high resolution of VTUF-3D is sufficient to examine the processes that drive human thermal comfort (HTC). This allows detailed calculations of surface temperatures, mean radiant temperature (Tmrt), and a HTC index, the universal thermal climate index (UTCI), across an urban canyon. An extensive validation process, using three different observation data sets to validate a number of different and key aspects of the VTUF-3D model, has shown it performs well and is suitable for use to examine critical questions relating to the role of vegetation and water in the urban environment. A demonstration of the model using modelling scenarios of varying canopy cover shows that average peak daytime HTC improvements of 1◦C UTCI (and 2.3◦C UTCI) are possible in doubling (and quadrupling) existing street cover canopies, with localised effects under canopy cover approaching 5◦C UTCI. These scenarios also show the value of the existing canopy cover, as reductions and elimination of existing cover can create reductions in HTC of 2◦C UTCI. In addition, reductions in average air temperature (Ta) across urban canyons can differ by 1◦C between streets with differing canopy cover. After the development, validation, and demonstration of this new model, it is now possible to conduct further analysis to quantify the impact each individual tree can have on temperatures in urban canyons. Further, the model can help inform the optimal arrangement and quantity of trees to maximise temperature moderation effects and be used to generate best practices guidelines for urban greening.

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