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Britcher, Colin P., John M. Wells, Benoit Renaud y Thibaut Buvat. "Aerodynamics of Urban Maglev vehicles". Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 226, n.º 6 (20 de marzo de 2012): 561–67. http://dx.doi.org/10.1177/0954409712441740.
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Some aerodynamic issues affecting low-speed Urban Maglev vehicles are studied, focusing primarily on the effect of ambient winds on levitation electromagnet loads. Aerodynamic characteristics of a representative vehicle are estimated by means of wind tunnel tests of a 1/12th scale model. The wind environment influencing the existing Maglev guideway at Old Dominion University are established from historical data. It is shown that ambient winds, particularly crosswinds, can pose significant challenges, including substantial redistribution of levitation forces among vehicle electromagnets. The development of large lateral forces, particularly at the forward electromagnet stations, may also be of concern.
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Romanic, Djordje, Ashkan Rasouli y Horia Hangan. "Urban wind resource assessment in changing climate: Case study". Wind Engineering 41, n.º 1 (1 de agosto de 2016): 3–12. http://dx.doi.org/10.1177/0309524x16653486.
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Urban wind resource assessment in changing climate has not been studied so far. This study presents a methodology for microscale numerical modelling of urban wind resource assessment in changing climate. The methodology is applied for a specific urban development in the city of Toronto, ON, Canada. It is shown that the speed of the southwest winds, that is, the most frequent winds increased for .8 m s−1 in the period from 1948 to 2015. The generated wind energy maps are used to estimate the influences of climate change on the available wind energy. It is shown that the geometry of irregularly spaced and located obstacles in urban environments has to be taken into consideration when performing studies on urban wind resource assessment in changing climate. In the analysed urban environment, peak speeds are more affected by climate change than the mean speeds.
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Kim, Hyungkyoo y Elizabeth Macdonald. "Wind and the city: An evaluation of San Francisco’s planning approach since 1985". Environment and Planning B: Urban Analytics and City Science 44, n.º 1 (28 de julio de 2016): 10–32. http://dx.doi.org/10.1177/0265813515607474.
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In 1985, San Francisco adopted a downtown plan on ground-level wind currents intended to mitigate the negative effects of wind on pedestrians’ perceived comfort in public open spaces. The plan mandates that new buildings in designated parts of the city associated with high density or development potential be designed or adopt measures to not cause wind in excess of accepted comfort levels. This study examines whether and to what degree the plan has successfully shaped an urban form that mitigates wind by comparing the ground-level wind environment in 1985 and 2013. A series of wind tunnel tests found that during San Francisco’s windiest season when the westerly winds are prevalent, the overall mean wind speed ratio measured at 318 locations in four areas of the city dropped by 22%. However, there still exist many excessively windy places that are associated with specific urban form conditions, including streets oriented to have direct exposure to westerly winds, flat façades on high-rise buildings, and horizontal street walls where building façades align. Recommendations based on the findings include incorporating more tangible guidance on the built form conditions, expanding the plan’s reach to cover more parts of the city, and learning from strategies used elsewhere. By evaluating the urban form impacts of a wind mitigation policy that has been in place for 30 years, the research offers insights for other cities that have implemented or plan to adopt similar approach and sheds light on issues related to wind comfort in high-density urban areas.
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Moreira, Davidson Martins y Taciana Toledo de Almeida Albuquerque. "Solution of the Atmospheric Diffusion Equation with Longitudinal Wind Speed Depending on Source Distance". Revista Brasileira de Meteorologia 31, n.º 2 (junio de 2016): 202–10. http://dx.doi.org/10.1590/0102-778631220150028.
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Abstract An integral semi-analytical solution of the atmospheric diffusion equation considering wind speed as a function of both downwind distance from a pollution source and vertical height is presented. The model accounts for transformation and removal mechanisms via both chemical reaction and dry deposition processes. A hypothetical dispersion of contaminants emitted from an urban pollution source in the presence of mesoscale winds in an unstable atmospheric boundary layer is showed. The results demonstrate that the mesoscale winds generated by urban heat islands advect contaminants upward, which increases the intensity of air pollution in urban areas.
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Giyasov, Adham I. y Timur B. Giyasov. "The importance of local winds for the aerationof urban areas having hot and windless climatic conditions". Vestnik MGSU, n.º 10 (octubre de 2020): 1363–71. http://dx.doi.org/10.22227/1997-0935.2020.10.1363-1371.
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Introduction. A city with its high-rise buildings, greenery and landscaping that prevent air motion aggravate windless conditions typical for climates in the cities located in the southern latitudes characterized by heat and lack of wind. Urban built-up areas have stagnant and overheated air that causes sultriness and significant air pollutions caused by anthropogenic sources. These factors require systematization of the local aerodynamics by means of local wind generation using solar energy.
Materials and methods. Methods of theoretical research, large-scale field measurements involving the use of instruments, visual observations by means of smoke screening of the urban area’s structure were applied and laboratory research into thermal and wind processes using physical models of cities were applied to identify the role of insolation in the generation of local thermal winds that improve the local environment on the micro- and macroscale.
Results. The author has found that if built-up urban areas have no general circulation wind fields, urban aeration systems develop local independent air flows due to the temperature difference between heat and cool islands. The temperature difference was applied as the source material for an urban wind model and it also helped to identify the dependence of the local wind velocity on the thermal contrast of urban islands. A classification of aeration models is developed at macro; meso-; micro- and nanoscales.
Conclusions. The practical area of application of the theory of hot and windless processes was identified in respect of urban area planning. The aerodynamics of an urban environment was systematized due to the generation of local thermal winds. The process of local thermal wind generation was studied; the classification of natural aeration models was made for urban areas. Methods of using solar energy were applied to generate local winds, to develop the microclimate and to enhance the environment of urban areas and structures as a prerequisite for targeted urban planning actions, three-dimensional space-planning solutions that apply to urban structures, landscaping, architectural and structural concepts of buildings.
Acknowledgments. The work was performed in accordance with the research schedule of Department of Design of Buildings and Structures, NRU MGSU, focused on “Function, Structure, Environment in the Architecture of Buildings and Towns”.
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Montero, Angel, M. Elias Dueker y Gregory D. O’Mullan. "Culturable bioaerosols along an urban waterfront are primarily associated with coarse particles". PeerJ 4 (22 de diciembre de 2016): e2827. http://dx.doi.org/10.7717/peerj.2827.
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The source, characteristics and transport of viable microbial aerosols in urban centers are topics of significant environmental and public health concern. Recent studies have identified adjacent waterways, and especially polluted waterways, as an important source of microbial aerosols to urban air. The size of these aerosols influences how far they travel, their resistance to environmental stress, and their inhalation potential. In this study, we utilize a cascade impactor and aerosol particle monitor to characterize the size distribution of particles and culturable bacterial and fungal aerosols along the waterfront of a New York City embayment. We seek to address the potential contribution of bacterial aerosols from local sources and to determine how their number, size distribution, and taxonomic identity are affected by wind speed and wind direction (onshore vs. offshore). Total culturable microbial counts were higher under offshore winds (average of 778 CFU/m3± 67), with bacteria comprising the majority of colonies (58.5%), as compared to onshore winds (580 CFU/m3± 110) where fungi were dominant (87.7%). The majority of cultured bacteria and fungi sampled during both offshore winds (88%) and onshore winds (72%) were associated with coarse aerosols (>2.1 µm), indicative of production from local sources. There was a significant correlation (p < 0.05) of wind speed with both total and coarse culturable microbial aerosol concentrations. Taxonomic analysis, based on DNA sequencing, showed that Actinobacteria was the dominant phylum among aerosol isolates. In particular,StreptomycesandBacillus, both spore forming genera that are often soil-associated, were abundant under both offshore and onshore wind conditions. Comparisons of bacterial communities present in the bioaerosol sequence libraries revealed that particle size played an important role in microbial aerosol taxonomy. Onshore and offshore coarse libraries were found to be most similar. This study demonstrates that the majority of culturable bacterial aerosols along a New York City waterfront were associated with coarse aerosol particles, highlighting the importance of local sources, and that the taxonomy of culturable aerosol bacteria differed by size fraction and wind direction.
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Celada-Murillo, Ana-Teresa, Susana Carreón-Sierra, Alejandro Salcido, Telma Castro, Oscar Peralta y Teodoro Georgiadis. "Main Characteristics of Mexico City Local Wind Events during the MILAGRO 2006 Campaign within a Meso-β Scale Lattice Wind Modeling Approach". ISRN Meteorology 2013 (4 de febrero de 2013): 1–14. http://dx.doi.org/10.1155/2013/605210.
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A characterization of local wind events in Mexico City, which occurred during MILAGRO campaign, was carried out within the framework of a lattice wind modeling approach at a meso-β scale. Mexico City was modeled as a 2D lattice domain with a given number of identical cells. Local wind conditions at any cell were described by a state variable defined by the spatial averages of wind attributes such as speed, direction, divergence, and vorticity. Full and partial densities of wind states were discussed under different conditions using two simple lattice wind models. We focus on the results obtained with the 1-cell lattice wind model and provide brief comments about preliminary results obtained with the 4-cell model. The 1-cell model allowed identifying the main patterns of the wind circulation in Mexico City throughout the study period (anabatic and katabatic winds, winds induced by the urban heat island, and winds with high possibilities for exchanging pollutants between Mexico City and the neighboring settlements, among others). The model showed that Mexico City wind divergence and vorticity disclose superposed oscillations whose most important periods were 24 and 12 hours, suggesting strong connections with the diurnal cycle of incoming solar radiation and the urban heat island.
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RAJ, P. ERNEST, P. C. S. DEVARA, R. S. MAHESKUMAR, G. PANDITHURAI y K. K. DANI. "Lidar-derived aerosol concentration and their relationship with horizontal winds over an urban location". MAUSAM 53, n.º 2 (18 de enero de 2022): 145–52. http://dx.doi.org/10.54302/mausam.v53i2.1630.
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Lidar-derived aerosol vertical profiles obtained at Pune, a low latitude tropical station, on about 535 days during a ten-year period (1987 – 96) along with simultaneous pilot-balloon wind (speed and direction) data of India Meteorological Department, Pune have been used in the study to investigate the influence of horizontal winds on the aerosol characteristics in the lower atmosphere. Aerosol column content in the atmospheric boundary layer (surface to 1100 m altitude above ground-level) as well as aerosol number density at the surface level (at 50 m) showed relatively higher values over the lidar site whenever the winds were blowing from the main urban and industrial regions of the city of Pune. This effect was found to be more pronounced during the winter season. Wind speeds also correlate well with increased aerosol loading, but only during selected high wind speed episodes. Thus the study shows that the short- and long-term increases in aerosol concentration/loading over the observation site are, to a large extent, influenced by horizontal winds in the surface layers and this in turn, can be attributed to the increasing human/urban activity around the lidar site over the years.
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Li, Gang, Juan Cui, Tingshan Liu, Yongqiu Zheng, Congcong Hao, Xiaojian Hao y Chenyang Xue. "Triboelectric-Electromagnetic Hybrid Wind-Energy Harvester with a Low Startup Wind Speed in Urban Self-Powered Sensing". Micromachines 14, n.º 2 (23 de enero de 2023): 298. http://dx.doi.org/10.3390/mi14020298.
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Wind energy as a renewable energy source is easily available and widely distributed in cities. However, current wind-energy harvesters are inadequate at capturing energy from low-speed winds in urban areas, thereby limiting their application in distributed self-powered sensor networks. A triboelectric–electromagnetic hybrid harvester with a low startup wind speed (LSWS-TEH) is proposed that also provides output power within a wide range of wind speeds. An engineering-implementable propeller design method is developed to reduce the startup wind speed of the harvester. A mechanical analysis of the aerodynamics of the rotating propeller is performed, and optimal propeller parameter settings are found that greatly improved its aerodynamic torque. By combining the high-voltage output of the triboelectric nanogenerator under low-speed winds with the high-power output of the electromagnetic generator under high-speed winds, the harvester can maintain direct current output over a wide wind-speed range after rectification. Experiments show that the harvester activates at wind speeds as low as 1.2 m/s, powers a sensor with multiple integrated components in 1.7 m/s wind speeds, and drives a Bluetooth temperature and humidity sensor in 2.7 m/s wind speeds. The proposed small, effective, inexpensive hybrid energy harvester provides a promising way for self-powered requirements in smart city settings.
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Moroni, Monica y Antonio Cenedese. "Laboratory Simulations of Local Winds in the Atmospheric Boundary Layer via Image Analysis". Advances in Meteorology 2015 (2015): 1–34. http://dx.doi.org/10.1155/2015/618903.
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In the atmospheric boundary layer, under high pressure conditions and negligible geostrophic winds, problems associated with pollution are the most critical. In this situation local winds play a major role in the evaluation of the atmospheric dynamics at small scales and in dispersion processes. These winds originate as a result of nonuniform heating of the soil, either when it is homogeneous or in discontinuous terrain in the presence of sea and/or slopes. Depending on the source of the thermal gradient, local winds are classified into convective boundary layer, sea and land breezes, urban heat islands, and slope currents. Local winds have been analyzed by (i) simple analytical models; (ii) numerical models; (iii) field measurements; (iv) laboratory measurements through which it is impossible to completely create the necessary similarities, but the parameters that determine the phenomenon can be controlled and each single wind can be separately analyzed. The present paper presents a summary of laboratory simulations of local winds neglecting synoptic winds and the effects of Coriolis force. Image analysis techniques appear suitable to fully describe both the individual phenomenon and the superposition of more than one local wind. Results do agree with other laboratory studies and numerical experiments.
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Zhang, Da-Lin, Menglin S. Jin, Yixuan Shou y Chunqing Dong. "The Influences of Urban Building Complexes on the Ambient Flows over the Washington–Reston Region". Journal of Applied Meteorology and Climatology 58, n.º 6 (junio de 2019): 1325–36. http://dx.doi.org/10.1175/jamc-d-19-0037.1.
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AbstractThis paper examines the collective impacts of urban building complexes on the planetary boundary layer (PBL) winds using both observations and a mesoscale model. Horizontal winds measured on the rooftops of federal buildings over the regions of Washington, D.C., and a small city nearby (i.e., Reston, Virginia) show the blocking effects of urban building complexes on the downstream winds during the daytime of 9 July 2007. A modeling study of the case using a coupled version of the Weather Research and Forecasting (WRF)–multilayer urban canopy model in which the observed building height and density information is implemented to advance the calculations of momentum and heat, reproduces the rooftop-observed wind patterns and the related urban heat island effects, especially the wake flows on the downstream sides of the above-mentioned two cities. Results show that under daytime conditions the building complexes can collectively form a mesoscale wake on the downwind side of each city, about 2–10 km away, horizontally from the edge of the building complexes. The wake flow may extend to much higher levels than the building tops, depending on the incoming flow strength, the static stability in the PBL, the height of the building complexes, and the time of the day because of the strength of surface insolation.
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Jung, J., Y. Miyazaki y K. Kawamura. "Different characteristics of new particle formation between urban and deciduous forest sites in Northern Japan during the summers of 2010–2011". Atmospheric Chemistry and Physics Discussions 12, n.º 6 (6 de junio de 2012): 14043–87. http://dx.doi.org/10.5194/acpd-12-14043-2012.
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Abstract. To investigate new particle formation (NPF) events in urban and forest environments, number size distributions of ultrafine particles were measured at an urban site and a deciduous forest site in Sapporo, Northern Japan, during the summers of 2011 and 2010, respectively. The burst of nucleation mode particles at the urban site typically started in the morning (7:00–11:30 local time, LT) with simultaneous increases in SO2 and O3 concentrations and the UV index under clear (sunny) weather conditions. The growth rates of nucleated particles at the urban site ranged from 5.0 to 7.8 nm h−1 with an average of 6.3 ± 1.1 nm h−1. NPF events at the urban site were separated into events with or without subsequent particle growth after the burst of nucleation mode particles. This division was related to prevailing wind direction as the subsequent growth of freshly nucleated particles typically occurred when wind direction shifted to northwesterly (from residential and public park areas), whereas it did not occur under southeasterly winds (from the downtown area). During the periods with NPF events, elevated concentrations of non-methane hydrocarbons (NMHC) were obtained under conditions of northwesterly winds when compared to southeasterly winds, whereas no difference in SO2 levels was recorded. These results suggest that variations in NMHC concentration may play an important role in the growth of freshly nucleated particles at the urban site. The burst of nucleation mode particles at the forest site typically started around noon (10:30–14:30 LT), which was 3–4 h later than that at the urban site. Interestingly, at the forest site the burst of nucleation mode particles usually started when air masses originating from urban Sapporo arrived at the forest site. The present study indicates that the inflow of these urban air masses acted as a trigger for the initiation of the burst of nucleation mode particles in the deciduous forest.
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Jung, J., Y. Miyazaki y K. Kawamura. "Different characteristics of new particle formation between urban and deciduous forest sites in Northern Japan during the summers of 2010–2011". Atmospheric Chemistry and Physics 13, n.º 1 (4 de enero de 2013): 51–68. http://dx.doi.org/10.5194/acp-13-51-2013.
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Abstract. To investigate new particle formation (NPF) events in urban and forest environments, number size distributions of ultrafine particles were measured at an urban site and a deciduous forest site in Sapporo, Northern Japan, during the summers of 2011 and 2010, respectively. The burst of nucleation mode particles at the urban site typically started in the morning (07:00–11:30 local time, LT) with simultaneous increases in SO2 and O3 concentrations and the UV index under clear (sunny) weather conditions. The growth rates of nucleated particles at the urban site ranged from 5.0 to 7.8 nm h−1 with an average of 6.3 ± 1.1 nm h−1. NPF events at the urban site were separated into events with or without subsequent particle growth after the burst of nucleation mode particles. This division was found to relate to prevailing wind direction because the subsequent growth of freshly nucleated particles typically occurred when wind direction shifted to northwesterly (from residential and public park areas), whereas it did not occur under southeasterly winds (from the downtown area). During the periods with NPF events, elevated concentrations of non-methane hydrocarbons (NMHC) were obtained under conditions of northwesterly winds when compared to southeasterly winds, whereas no difference in SO2 levels was recorded. These results suggest that variations in NMHC concentration may play an important role in the growth of freshly nucleated particles at the urban site. The burst of nucleation mode particles at the forest site typically started around noon (10:30–14:30 LT), which was 3–4 h later than that at the urban site. Interestingly, at the forest site the burst of nucleation mode particles usually started when air masses originating from urban Sapporo arrived at the forest site. The present study indicates that the inflow of these urban air masses acted as a trigger for the initiation of the burst of nucleation mode particles in the deciduous forest.
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Klein, Petra y James V. Clark. "Flow Variability in a North American Downtown Street Canyon". Journal of Applied Meteorology and Climatology 46, n.º 6 (1 de junio de 2007): 851–77. http://dx.doi.org/10.1175/jam2494.1.
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Abstract Previous field and laboratory studies have indicated that flow and turbulence inside urban areas and, in particular, in street canyons, is very complex and is associated with wakes and vortices developing near buildings. However, a number of open questions still exist, primarily with regard to which parameters determine the structure of street-canyon flow. The paper presents results from high-resolution wind measurements in a downtown urban street canyon in Oklahoma City, Oklahoma, that were conducted during the Joint Urban 2003 tracer experiment. Data collected with sonic anemometers on two towers installed on opposite sites of the street canyon, each with five different measurement levels, have been analyzed, and the variation of in-canyon flow and turbulence parameters with wind direction and atmospheric stability is discussed. It was found that the street-canyon flow is strongly channeled and its direction is determined by the along-canyon component of the above-roof-level winds. As a consequence, the direction of the street-level winds changes abruptly, and small variations of the upwind direction can significantly alter the in-canyon flow properties. Contrary to results from studies with idealized street canyons, the along-canyon flow components remained significant even for conditions with winds approaching the street at almost perpendicular angles. For such wind directions, a tendency toward development of street-canyon vortices with pronounced vertical motions have been found. However, the complex building geometries at the chosen measurement site enhance the complexity of the flow patterns, and situations with a classic street-canyon vortex rotating in the street could not be identified. In addition, the comprehensive dataset from the Joint Urban 2003 field campaign allowed detailed study of the influence of boundary layer stability on flow in the urban canopy layer. It has become clear that very different conclusions can be drawn with regard to these effects depending on the choice of reference values used in the analysis of the street-canyon data. Using winds from higher elevations in the atmospheric boundary layer (250 m) as reference data, one would conclude that atmospheric stability strongly influences in-canyon flow and, in particular, turbulence. However, only minor stability effects are still seen after normalization with wind speed values at average roof-level height (80 m). This choice allows one to conclude that the in-canyon flow is primarily driven by the boundary layer wind field at average roof level.
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Aquino-Martínez, Lourdes P., Arturo I. Quintanar, Carlos A. Ochoa-Moya, Erika Danaé López-Espinoza, David K. Adams y Aron Jazcilevich-Diamant. "Urban-Induced Changes on Local Circulation in Complex Terrain: Central Mexico Basin". Atmosphere 12, n.º 7 (14 de julio de 2021): 904. http://dx.doi.org/10.3390/atmos12070904.
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Land use land cover (LULC) significantly impacts local circulation in the Mexico Basin, particularly wind field circulations such as gap winds, convergence lines, and thermally induced upslope/downslope wind. A case study with a high-pressure system over the Mexico Basin isolates the influence of large-scale synoptic forcing. Numerical simulations reveal a wind system composed of meridional circulation and a zonal component. Thermal pressure gradients between the Mexico basin and its colder surroundings create near-surface convergence lines as part of the meridional circulation. Experiments show that the intensity and organization of meridional circulations and downslope winds increase when LULC changes from natural and cultivated land to urban. Zonal circulation exhibits a typical circulation pattern with the upslope flow and descending motion in the middle of the basin. Large values of moist static energy are near the surface where air parcels pick up energy from the surface either as fluxes of enthalpy or latent heat. Surface heat fluxes and stored energy in the ground are drivers of local circulation, which is more evident in zonal circulation patterns.
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Hendricks, Eric A. y Jason C. Knievel. "Evaluation of Urban Canopy Models against Near-Surface Measurements in Houston during a Strong Frontal Passage". Atmosphere 13, n.º 10 (22 de septiembre de 2022): 1548. http://dx.doi.org/10.3390/atmos13101548.
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Urban canopy models (UCMs) in mesoscale numerical weather prediction models need evaluation to understand biases in urban environments under a range of conditions. The authors evaluate a new drag formula in the Weather Research and Forecasting (WRF) model’s multilayer UCM, the Building Effect Parameterization combined with the Building Energy Model (BEP+BEM), against both in-situ measurements in the urban environment as well as simulations with a simple bulk scheme and BEP+BEM using the old drag formula. The new drag formula varies with building packing density, while the old drag formula is constant. The case study is a strong cold frontal passage that occurred in Houston during the winter of 2017, causing high winds. It is found that both BEP+BEM simulations have lower peak wind speeds, consistent with near-surface measurements, while the bulk simulation has winds that are too strong. The constant-drag BEP+BEM simulation has a near-zero wind speed bias, while the new-drag simulation has a negative bias. Although the focus is on the impact of drag on the urban wind speeds, both BEP+BEM simulations have larger negative biases in the near-surface temperature than the bulk-scheme simulation. Reasons for the different performances are discussed.
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James, Ken R. y Craig Hallam. "Stability of urban trees in high winds". Arboricultural Journal 35, n.º 1 (marzo de 2013): 28–35. http://dx.doi.org/10.1080/03071375.2013.783157.
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Coceal, O. y S. E. Belcher. "Mean Winds Through an Inhomogeneous Urban Canopy". Boundary-Layer Meteorology 115, n.º 1 (abril de 2005): 47–68. http://dx.doi.org/10.1007/s10546-004-1591-4.
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Finn, Dennis, Kirk L. Clawson, Roger G. Carter, Jason D. Rich y K. Jerry Allwine. "Plume Dispersion Anomalies in a Nocturnal Urban Boundary Layer in Complex Terrain". Journal of Applied Meteorology and Climatology 47, n.º 11 (1 de noviembre de 2008): 2857–78. http://dx.doi.org/10.1175/2008jamc1864.1.
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Abstract The URBAN 2000 experiments were conducted in the complex urban and topographical terrain in Salt Lake City, Utah, in stable nighttime conditions. Unexpected plume dispersion often arose because of the interaction of complex terrain and mountain–valley flow dynamics, drainage flows, synoptic influences, and urban canopy effects, all within a nocturnal boundary layer. It was found that plume dispersion was strongly influenced by topography, that dispersion can be significantly different than what might be expected based upon the available wind data, and that it is problematic to rely on any one urban-area wind measurement to predict or anticipate dispersion. Small-scale flows can be very important in dispersion, and their interaction with the larger-scale flow field needs to be carefully considered. Some of the anomalies observed include extremely slow dispersion, complicated recirculation dispersion patterns in which plume transport was in directions opposed to the measured winds, and flow decoupling. Some of the plume dispersion anomalies could only be attributed to small-scale winds that were not resolved by the existing meteorological monitoring network. The results shown will make clear the difficulties in modeling or planning for emergency response to toxic releases in a nocturnal urban boundary layer within complex terrain.
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Tapajós, Raphael Pablo, Rodrigo Da Silva, Wilderclay Barreto Machado, Raoni Silva de Santana, Roseilson Do Vale y Miércio Jorge Ferreira-Junior. "ANÁLISE DAS CARACTERÍSTICAS DO VENTO SOBRE A FLORESTA NACIONAL DO TAPAJÓS, PARÁ, BRASIL". Ciência e Natura 38 (20 de julio de 2016): 204. http://dx.doi.org/10.5902/2179460x20171.
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The atmospheric circulation of the Tapajós River region has unique characteristics due to influences of forests, agricultural fields, rivers and urban areas. The study with regard to the wind field in two different points in National Forest Tapajós (FNT) shows that there are significant differences in wind direction at those points. Identifying and quantify of the North and South canalization, and westerly winds, give important indications for studying the influence of different areas on the FNT. The results show that the occurrences of drains and west winds are more present during the rainy season and occur more during the day. Furthermore, in Jamaraquá station nearest to the River, the influence of channeling and west winds are greater, which can be due not only proximity of river but also the topographical features.
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Lundquist, Julie K. y Stevens T. Chan. "Consequences of Urban Stability Conditions for Computational Fluid Dynamics Simulations of Urban Dispersion". Journal of Applied Meteorology and Climatology 46, n.º 7 (1 de julio de 2007): 1080–97. http://dx.doi.org/10.1175/jam2514.1.
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Abstract The validity of omitting stability considerations when simulating transport and dispersion in the urban environment is explored using observations from the Joint Urban 2003 field experiment and computational fluid dynamics simulations of that experiment. Four releases of sulfur hexafluoride, during two daytime and two nighttime intensive observing periods (IOPs), are simulated using the building-resolving computational fluid dynamics model called the Finite Element Model in 3-Dimensions and Massively Parallelized (FEM3MP) to solve the Reynolds-averaged Navier–Stokes equations with two options of turbulence parameterizations. One option omits stability effects but has a superior turbulence parameterization using a nonlinear eddy viscosity (NEV) approach, and the other considers buoyancy effects with a simple linear eddy viscosity approach for turbulence parameterization. Model performance metrics are calculated by comparison with observed winds and tracer data in the downtown area and with observed winds and turbulence kinetic energy (TKE) profiles at a location immediately downwind of the central business district in the area labeled as the urban shadow. Model predictions of winds, concentrations, profiles of wind speed, wind direction, and friction velocity are generally consistent with and compare reasonably well to the field observations. Simulations using the NEV turbulence parameterization generally exhibit better agreement with observations. To explore further the assumption of a neutrally stable atmosphere within the urban area, TKE budget profiles slightly downwind of the urban wake region in the urban shadow are examined. Dissipation and shear production are the largest terms that may be calculated directly. The advection of TKE is calculated as a residual; as would be expected downwind of an urban area, the advection of TKE produced within the urban area is a very large term. Buoyancy effects may be neglected in favor of advection, shear production, and dissipation. For three of the IOPs, buoyancy production may be neglected entirely; for one IOP, buoyancy production contributes approximately 25% of the total TKE at this location. For both nighttime releases, the contribution of buoyancy to the total TKE budget is always negligible though positive. Results from the simulations provide estimates of the average TKE values in the upwind, downtown, downtown shadow, and urban wake zones of the computational domain. These values suggest that building-induced turbulence can cause the average turbulence intensity in the urban area to increase by as much as 7 times average upwind values, explaining the minimal role of buoyant forcing in the downtown region. The downtown shadow exhibits an exponential decay in average TKE, whereas the distant downwind wake region approaches the average upwind values. For long-duration releases in downtown and downtown shadow areas, the assumption of neutral stability is valid because building-induced turbulence dominates the budget. However, farther downwind in the urban wake region, which is found to be approximately 1500 m beyond the perimeter of downtown Oklahoma City, Oklahoma, the levels of building-induced turbulence greatly subside, and therefore the assumption of neutral stability is less valid.
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Cole, Jason, David J. Nowak y Eric J. Greenfield. "Potential Hurricane Wind Risk to US Rural and Urban Forests". Journal of Forestry 119, n.º 4 (30 de abril de 2021): 393–406. http://dx.doi.org/10.1093/jofore/fvab018.
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Abstract Hurricanes cause billions of dollars in damage annually in the United States and are projected to increase in intensity in the coming years. By exploring historical patterns of hurricanes and exposure of these hurricane-force winds across the landscape, areas of potentially high threat to future hurricane winds can be revealed. Combining potential threats from hurricane winds with forest data reveal the areas with the greatest potential threats to this important resource. Not surprisingly, most of the threats to forests occur in the Southeast, but the greatest threats to urban forests overall occur along the Northeast coast and in metropolitan centers in the Southeast. Overall, 4.6% of the nation’s rural forest basal area is within zones of the highest risk from hurricane winds. Information on regional and local scale variations in hurricane risk can be used to aid policies and local forest management to improve forest health and sustainability.
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Liu, Xueling, Arthur P. Mizzi, Jeffrey L. Anderson, Inez Fung y Ronald C. Cohen. "The potential for geostationary remote sensing of NO<sub>2</sub> to improve weather prediction". Atmospheric Chemistry and Physics 21, n.º 12 (24 de junio de 2021): 9573–83. http://dx.doi.org/10.5194/acp-21-9573-2021.
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Abstract. Observations of winds in the planetary boundary layer remain sparse making it challenging to simulate and predict atmospheric conditions that are most important for describing and predicting urban air quality. Short-lived chemicals are observed as plumes whose location is affected by boundary layer winds and whose lifetime is affected by boundary layer height and mixing. Here we investigate the application of data assimilation of NO2 columns as will be observed from geostationary orbit to improve predictions and retrospective analysis of wind fields in the boundary layer.
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Rendón, Angela M., Juan F. Salazar, Carlos A. Palacio, Volkmar Wirth y Björn Brötz. "Effects of Urbanization on the Temperature Inversion Breakup in a Mountain Valley with Implications for Air Quality". Journal of Applied Meteorology and Climatology 53, n.º 4 (abril de 2014): 840–58. http://dx.doi.org/10.1175/jamc-d-13-0165.1.
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AbstractMany cities located in valleys with limited ventilation experience serious air pollution problems. The ventilation of an urban valley can be limited not only by orographic barriers, but also by urban heat island–induced circulations and/or the capping effect of temperature inversions. Furthermore, land-use/-cover changes caused by urbanization alter the dynamics of temperature inversions and urban heat islands, thereby affecting air quality in an urban valley. By means of idealized numerical simulations, it is shown that in a mountain valley subject to temperature inversions urbanization can have an important influence on air quality through effects on the inversion breakup. Depending on the urban area fraction in the simulations, the breakup time changes, the cross-valley wind system can evolve from a confined to an open system during the daytime, the slope winds can be reversed by the interplay between the urban heat island and the temperature inversion, and the breakup pattern can migrate from one dominated by the growth of the convective boundary layer to one also involving the removal of mass from the valley floor by the upslope winds. The analysis suggests that the influence of urbanization on the air quality of an urban valley may lead to contrasting and possibly counterintuitive effects when considering temperature inversions. More urban land does not necessarily imply worse air quality, even when considering that the amount of pollutants emitted grows with increased urbanization.
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Shin, Youngkyu, Sangnam Park, Hyerngdu Yun y Myungsuk Yu. "Urban Wind Field Mapping Technique for Municipal Environmental Planning: A Case Study of Cheongju-Si, Korea". Atmosphere 13, n.º 11 (31 de octubre de 2022): 1805. http://dx.doi.org/10.3390/atmos13111805.
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The integrated management of land and environmental plans (EPs) has been a key direction of sustainable policy in Korea. Although local EPs should be established based on spatial data, much of the pertinent environmental information has not been mapped. Accordingly, we develop a wind field mapping technique for establishing local EPs. This method was developed via a numerical weather prediction model (Weather Research and Forecast—WRF), and a diagnostic meteorological model (California Meteorological model—CALMET), based on weather observation data, as well as terrain and land cover data. The developed method was applied to a case study in Cheongju-si, Korea, for verifying its effectiveness. The created wind field maps of Cheongju-si provided an intuitive visual representation of the spatial distribution of seasonal and daytime/nighttime wind patterns. Such data helped understand the directionality and patterns of winds blowing into a city, or identify stagnant areas of wind circulation. Overlaying the wind field map with maps of air pollutant emissions revealed that pollutants from industrial areas could flow along the prevailing winds into residential areas downtown. These maps also implied that open spaces, such as parks and grasslands, were recommendable for stagnant areas, instead of creating industrial complexes or residential areas.
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Duryea, Mary, George Blakeslee, William Hubbard y Ricardo Vasquez. "Wind and Trees: A Survey of Homeowners After Hurricane Andrew". Arboriculture & Urban Forestry 22, n.º 1 (1 de enero de 1996): 44–50. http://dx.doi.org/10.48044/jauf.1996.006.
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The destructive winds of Hurricane Andrew dramatically changed the urban forest in Dade County, Florida on August 24,1992. Overnight, the tree canopy was replaced by a landscape of broken, uprooted, defoliated and severely damaged trees. To assist communities in reforestation efforts, scientists at the University of Florida conducted a homeowner survey to determine how different tree species responded to strong winds. Native tree species, such as box leaf stopper, sabal palm gumbo limbo, and live oak were the best survivors of the winds. Other palms such as areca, cabada, and Alexander were also highly wind resistant. In general, fruit trees such as navel orange, mango, avocado and grapefruit were severely damaged. Black olive, live oak, and gumbo limbo trees that were pruned survived the hurricane better than unpruned trees. Only 18% of all the trees that fell caused property damage. Hurricane-susceptible communities should consider wind resistance as one of their criteria in tree species selection.
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Baik, Jong-Jin, Seung-Bu Park y Jae-Jin Kim. "Urban Flow and Dispersion Simulation Using a CFD Model Coupled to a Mesoscale Model". Journal of Applied Meteorology and Climatology 48, n.º 8 (1 de agosto de 2009): 1667–81. http://dx.doi.org/10.1175/2009jamc2066.1.
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Abstract Flow and pollutant dispersion in a densely built-up area of Seoul, Korea, are numerically examined using a computational fluid dynamics (CFD) model coupled to a mesoscale model [fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)]. The CFD model used is a Reynolds-averaged Navier–Stokes equations model with the renormalization group k − ɛ turbulence model. A one-way nesting method is employed in this study. MM5-simulated data are linearly interpolated in time and space to provide time-dependent boundary conditions for the CFD model integration. In the MM5 simulation, four one-way nested computational domains are considered, and the innermost domain with a horizontal grid size of 1 km covers the Seoul metropolitan area and its adjacent areas, including a part of the Yellow Sea. The NCEP final analysis data are used as initial and boundary conditions for MM5. MM5 is integrated for 48 h starting from 0300 LST 1 June 2004 and the coupled CFD–MM5 model is integrated for 24 h starting from 0300 LST 2 June 2004. During the two-day period, a high-pressure system was dominant over the Korean peninsula, with clear conditions and weak synoptic winds. MM5 simulates local circulations characterized by sea breezes and mountain/valley winds. MM5-simulated synoptic weather and near-surface temperatures and winds are well matched with the observed ones. Results from the coupled CFD–MM5 model simulation show that the flow in the presence of real building clusters can change significantly as the ambient wind speed and direction change. Diurnally varying local circulations mainly cause changes in ambient wind speed and direction in the present simulation. Some characteristic flows—such as the double-eddy circulation, channeling flow, and vertical recirculation vortex—are simulated. Pollutant dispersion pattern and the degree of lateral pollutant dispersion are shown to be complicated in the presence of real building clusters and under varying ambient wind speed and direction. This study suggests that because of the sensitive dependency of urban flow and pollutant dispersion on variations in ambient wind, time-dependent boundary conditions should be used to better simulate or predict them when the ambient wind varies over the period of CFD model simulation.
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Lopes, António, Elis Alves, Maria João Alcoforado y Raquel Machete. "Lisbon Urban Heat Island Updated: New Highlights about the Relationships between Thermal Patterns and Wind Regimes". Advances in Meteorology 2013 (2013): 1–11. http://dx.doi.org/10.1155/2013/487695.
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Urban growth implies significant modifications in the urban climate. To understand the influence of the city of Lisbon on the urban boundary layer, a mesoscale meteorological network was installed in 2004. The main goals of the present study are to update the results of the research published in 2007 and to bring more precise information about the relationship between the Urban Heat Island (UHI) and the regional and local wind systems. The highest frequencies of the UHI were found in the city centre (Restauradores). In the green park of Monsanto, the highest frequency occurred between −2 and 0°C. During the summer, the effect of the breezes was observed in Belém, lowering the temperature. The “strong” UHI (intensity >4°C) occurred more often during the summer, with median values of 2°C by night and 1.8°C by day. The highest frequencies of UHI occurred for winds between 2 and 6 m/s and were not associated with atmospheric calm, as pointed out in the literature. Winds above 8 m/s inhibit the occurrence of strong UHI in Lisbon. Summer nighttime strong UHI should be further investigated, due to the heat stress consequences on the population and probable increase of energy consumption.
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Sokolskaya, Oksana N. y Vlada V. Karanova. "Climate-based city zoning with regard for the wind conditions of the city of Novorossiysk". Stroitel'stvo: nauka i obrazovanie [Construction: Science and Education] 12, n.º 4 (30 de diciembre de 2022): 33–45. http://dx.doi.org/10.22227/2305-5502.2022.4.3.
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Introduction. Local nature, the climate, the sea, and the mountainous terrain influence the development of the built-up environment in Novorossiysk. These factors make a large contribution to the microclimate index of the urban atmosphere, and they must be taken account in the course of urban planning and architectural designing. Materials and methods. Advanced weather models, used in applied meteorology, such as ICON, GFS and GEM, which take into account the climatic features of the Black Sea coast, and unique whole-year wind patterns, typical for the area, were used in this scientific research. Results. The authors suggested introducing climate-based city zoning into the urban planning practice of Novorossiysk. In particular, the residential area on the west coast of the Tsemesskaya Bay along the Black Sea coast can be divided into the two main parts: the development area, whose mission is to protect urban spaces from strong winds, reaching high velocities in the winter season, and the development zone that triggers moderate breezes in the warm season. Principal urban planning and architectural design recommendations were developed for both territories. Conclusions. Climate-based city zoning, if introduced into practical urban planning, will substantially improve the microclimate indices of development areas in the summer time by facilitating favourable breezes and limiting access for extremely cold winds, blowing from the north-east in winter, if the architectural, structural and space planning recommendations are implemented.
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Ishida, Yasuyuki, Akihito Yoshida, Shuhei Kamata, Yuta Yamane y Akashi Mochida. "Wind Tunnel Experiments on Interference Effects of a High-Rise Building on the Surrounding Low-Rise Buildings in an Urban Block". Wind 3, n.º 1 (21 de febrero de 2023): 97–114. http://dx.doi.org/10.3390/wind3010007.
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High-rise buildings cause accelerated winds around them. However, the interference effects of high-rise buildings on the surrounding low-rise buildings in urban blocks have not been evaluated. This study investigated the wind pressure coefficients on the roofs and walls of low-rise buildings surrounding a high-rise building through wind tunnel experiments. Seventy-two wind directions were considered from 0° to 355° in 5° increments, and the influence of the wind direction on the wind pressure coefficients of surrounding buildings was evaluated. At a 30° wind direction angle, the positive and negative peak wind pressure coefficients occurred in a low-rise building at the leeward side of the high-rise building. The positive peak pressure, approximately 1.4 times that without a nearby high-rise building, occurred at the windward corner on the front wall of a low-rise building. The negative peak value, approximately three times that without a nearby high-rise building, was observed at the windward edge on the roof of a low-rise building. Thus, accelerated winds caused by high-rise buildings may result in unexpected damage to the surrounding low-rise buildings.
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dos Santos, Vânia Raposo de Moura y Gustavo Melo. "Influence of microclimatic elements on sound propagation in Amazonian cities: The case of urban noise in Belem." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, n.º 1 (1 de agosto de 2021): 5708–19. http://dx.doi.org/10.3397/in-2021-3232.
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Many studies have shown that microclimatic elements influence the sound propagation in cities, and can contribute to increasing or decreasing the urban noise. This paper aims to discuss the relationship between main microclimatic elements - air temperature, air humidity, atmospheric pressure and winds - and the noise caused by road traffic in an Amazonian urban environment, in order to emphasize the importance of urban planning instruments be adapted to the specific microclimatic conditions, promoting the improvement of the urban environment from more efficient building strategies for controlling the sound pollution. For this, it's used as basis a theoretical framework on the topic, meteorological data from Brazil's National Institute of Meteorology and illustrative maps of the city of Belem. It was found that the temperature, humidity and atmospheric pressure, for this microclimate, do not collaborate for reducing road traffic noise, leaving this responsibility to the winds (air ventilation) and the way they behave within the built urban mass. KEYS Urban noise - Urban Microclimate - Amazonian environment
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Vita, Giulio, Zhenru Shu, Michael Jesson, Andrew Quinn, Hassan Hemida, Mark Sterling y Chris Baker. "On the assessment of pedestrian distress in urban winds". Journal of Wind Engineering and Industrial Aerodynamics 203 (agosto de 2020): 104200. http://dx.doi.org/10.1016/j.jweia.2020.104200.
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Coceal, O. y S. E. Belcher. "A canopy model of mean winds through urban areas". Quarterly Journal of the Royal Meteorological Society 130, n.º 599 (abril de 2004): 1349–72. http://dx.doi.org/10.1256/qj.03.40.
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Hamel, David, Matthew Chwastek, Saturnino Garcia, Bakhtier Farouk, Moshe Kam y Kapil R. Dandekar. "Sensor Placement for Urban Homeland Security Applications". International Journal of Distributed Sensor Networks 6, n.º 1 (1 de enero de 2010): 859263. http://dx.doi.org/10.1155/2010/859263.
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We simulated a sensor network that detects and tracks the release of harmful airborne contaminants in an urban environment. The simulation determines sensor placement in that environment. The effort required integration of models from computational fluid dynamics (CFDs), combinatorial optimization, and population mobility dynamics. These CFD models, coupled with population mobility models, facilitate estimation of the effect of released contaminant on civilian populations. We studied the effects of a contaminant, chlorine gas, as a function of urban environment, prevailing winds, and likely attack locations. The models predictions optimized sensor node locations, providing mitigation of contaminant effects on human population. Results show that higher fidelity dispersal predictions increase sensor placement effectiveness. Incorporation of civilian evacuation models helps to minimize the overall impact of an attack when compared to a static population. Moreover, results show the benefits of using seasonal sensor configurations to maximize detection capabilities, taking into account prevailing seasonal wind conditions.
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Siddharth Jena y Ajay Gairola. "Numerical Method to Generate and Evaluate Environmental Wind Over Hills: Comparison of Pedestrian Winds Over Hills and Plains". CFD Letters 14, n.º 10 (28 de octubre de 2022): 56–67. http://dx.doi.org/10.37934/cfdl.14.10.5667.
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It is well known that the wind profile at altitudes below 10m from mean sea level (MSL) depends on the geometry of terrain, due to the boundary layer phenomenon. Hence, the profile of wind changes for hilly terrains and mountainous regions when compared with the plain regions. This phenomenon has become important to study due to the large-scale urbanisation taking place over hilly regions. The changing wind profile presents a challenge to evaluate the pedestrian winds, as depending on the aspect of the terrain an additional vertical velocity component is experienced due to the upwind climb of the winds. This creates a wind profile that is twisted in form. While wind tunnel studies have attempted to recreate this twisted wind profile (TWP), due to the inherent deficiency of wind tunnels to simultaneously map velocity and flow conditions, a lack of three-dimensional flow profile hinders pedestrian comfort evaluation. In the wind tunnel studies, it was also observed that small vertical eddies and wakes behind the interfering building were not identified which are an important factor to determine the pollution load dispersion. The authors have developed a numerical model to generate the twisted wind profile. The specialty of the numerical model lies in it’s unique boundary conditions that enable the visualization and quantification of the complete 3D wind profile, when the wind over a hilly terrain interacts with urban infrastructures. The developed model was validated with the wind tunnel experiments done previously by Tse and colleagues. The specialty of the model is that it ensures horizontal homogeneity while creating vertical heterogeneity. From the 3D flow profile hence generated the authors were able to deduce that the impact of twisted wind profile depends on the yaw angle of wind interacting with the structure and not on the wind attack angle. Also, the more the twist of the wind, more is the clockwise shifting of the far wakes behind the building. It was also seen that there are more low velocity zones in the pedestrian winds over a hill in comparison to that over the plains. The vertical eddies that aid in convective removal of pollutants were also missing in case of pedestrian winds over hilly terrains, which raises the risk of pollutant accumulation. The same was also observed in Hong-Kong during COVID 19, where due to the twisted nature of wind flow, the virus load increased and natural ventilation was inadequate in the removal of the viral load in the air near urban areas.
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Miller, Colton, Susan O’Neill, Miriam Rorig y Ernesto Alvarado. "Air-Quality Challenges of Prescribed Fire in the Complex Terrain and Wildland Urban Interface Surrounding Bend, Oregon". Atmosphere 10, n.º 9 (3 de septiembre de 2019): 515. http://dx.doi.org/10.3390/atmos10090515.
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Prescribed fires in forest ecosystems can negatively impact human health and safety by transporting smoke downwind into nearby communities. Smoke transport to communities is known to occur around Bend, Oregon, United States of America (USA), where burning at the wildland–urban interface in the Deschutes National Forest resulted in smoke intrusions into populated areas. The number of suitable days for prescribed fires is limited due to the necessity for moderate weather conditions, as well as wind directions that do not carry smoke into Bend. To better understand the conditions leading to these intrusions and to assess predictions of smoke dispersion from prescribed fires, we collected data from an array of weather and particulate monitors over the autumn of 2014 and spring of 2015 and historical weather data from nearby remote automated weather stations (RAWS). We characterized the observed winds to compare with meteorological and smoke dispersion models using the BlueSky smoke modeling framework. The results from this study indicated that 1–6 days per month in the spring and 2–4 days per month in the fall met the general meteorological prescription parameters for conducting prescribed fires in the National Forest. Of those, 13% of days in the spring and 5% of days in the fall had “ideal” wind patterns, when north winds occurred during the day and south winds did not occur at night. The analysis of smoke intrusions demonstrated that dispersion modeling can be useful for anticipating the timing and location of smoke impacts, but substantial errors in wind speed and direction of the meteorological models can lead to mischaracterizations of intrusion events. Additionally, for the intrusion event modeled using a higher-resolution 1-km meteorological and dispersion model, we found improved predictions of both the timing and location of smoke delivery to Bend compared with the 4-km meteorological model. The 1-km-resolution model prediction fell within 1 h of the observed event, although with underpredicted concentrations, and demonstrated promise for high-resolution modeling in areas of complex terrain.
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Wang, Fan, Gregory R. Carmichael, Jing Wang, Bin Chen, Bo Huang, Yuguo Li, Yuanjian Yang y Meng Gao. "Circulation-regulated impacts of aerosol pollution on urban heat island in Beijing". Atmospheric Chemistry and Physics 22, n.º 20 (18 de octubre de 2022): 13341–53. http://dx.doi.org/10.5194/acp-22-13341-2022.
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Abstract. Unprecedented urbanization in China has led to serious urban heat island (UHI) issues, exerting intense heat stress on urban residents. Based on the observed temperature and PM2.5 concentrations in Beijing over 2016–2020, we find diverse influences of aerosol pollution on urban heat island intensity (UHII) under different circulations. When northerly winds are prevalent in urban Beijing, UHII tends to be much higher in both daytime and nighttime and it is less affected by aerosol concentrations. However, when southerly and westerly winds are dominant in rural Beijing, UHII is significantly reduced by aerosol pollution. Using coupled aerosol-radiation weather simulations, we demonstrate the underlying physical mechanism which is associated with local circulation and resulting spatial distribution of aerosols. Our results also highlight the role of black carbon in aggravating UHI, especially during nighttime. It could thus be targeted for cooperative management of heat islands and aerosol pollution.
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You, Jangyoul y Changhee Lee. "Experimental Study on the Effects of Aspect Ratio on the Wind Pressure Coefficient of Piloti Buildings". Sustainability 13, n.º 9 (6 de mayo de 2021): 5206. http://dx.doi.org/10.3390/su13095206.
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Owing to strong winds during the typhoon season, damage to pilotis in the form of dropout of the exterior materials occurs frequently. Pilotis placed at the end exhibit a large peak wind pressure coefficient of the ceiling. In this study, the experimental wind direction angle of wind pressure tests was conducted in seven directions, with wind test angles varying from 0° to 90° at intervals of 15°, centered on the piloti position, which was accomplished using the wind tunnel experimental system. Regardless of the height of the building, the maximum peak wind pressure coefficient was observed at the center of the piloti, whereas the minimum peak wind pressure coefficient was noted at the corners, which corresponds with the wind direction inside the piloti. The distribution of the peak wind pressure coefficient was similar for both suburban and urban environments. However, in urban areas, the maximum peak wind pressure coefficient was approximately 1.4–1.7 times greater than that in suburban areas. The maximum peak wind pressure coefficient of the piloti ceiling was observed at the inside corner, whereas the minimum peak wind pressure coefficient was noted at the outer edge of the ceiling. As the height of the building increased, the maximum peak wind pressure coefficient decreased. Suburban and urban areas exhibited similar peak wind pressure distributions; however, the maximum peak wind pressure coefficient in urban areas was approximately 1.2–1.5 times larger than that in suburban areas.
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Zarei, Mohammad, Seyyed Ashkezari y Mehrdad Yari. "The investigation of the function of the central courtyard in moderating the harsh environmental conditions of a hot and dry climate (Case study: City of Yazd, Iran)". Spatium, n.º 38 (2017): 1–9. http://dx.doi.org/10.2298/spat1738001z.
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As one of the arid areas of Iran, Yazd is always exposed to extreme winds with dust and shifting sands. Therefore, the architectural principles in the residential architecture of the city need be adapted to such environmental conditions in order to minimize the influence of the severe winds on the interior spaces. This study investigates the influence of storms on the interior space of the central courtyards in Yazd, constructed during the Muzaffarid, Safavid and Qajar periods using CFD simulation. Three-dimensional models were prepared via Gambit software and studied in Fluent software. The wind speed entering the computing field was equal to 26.4m/s and the Dutch wind nuisance standard NEN 8100 was applied as the comfort criterion. The results showed a relationship between the extent of the central courtyard and the impact of severe storms on it, since an increase in the area of the courtyard provides enough space for the wind flow and move around it. This feature reaches its climax if the length to height proportion increases, as the wind brings the shifting sands into large courtyards, therefore, the architects tried to provide better conditions by creating microclimates.
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Dou, Jingjing, Yingchun Wang, Robert Bornstein y Shiguang Miao. "Observed Spatial Characteristics of Beijing Urban Climate Impacts on Summer Thunderstorms". Journal of Applied Meteorology and Climatology 54, n.º 1 (enero de 2015): 94–105. http://dx.doi.org/10.1175/jamc-d-13-0355.1.
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AbstractThis study investigates interactive effects from the Beijing urban area on temperature, humidity, wind speed and direction, and precipitation by use of hourly automatic weather station data from June to August 2008–12. Results show the Beijing summer urban heat island (UHI) as a multicenter distribution (corresponding to underlying land-use features), with stronger nighttime than daytime values (averages of 1.7° vs 0.8°C, respectively). Specific humidity was lower in urban Beijing than in surrounding nonurban areas, and this urban dry island is stronger during day than night (maximum of −2.4 vs −1.9 g kg−1). Wind direction is affected by both a mountain–valley-breeze circulation and by urbanization. Morning low-level flows converged into the strong UHI, but afternoon and evening southerly winds were bifurcated by an urban building-barrier-induced divergence. Summer thunderstorms also thus bifurcated and bypassed the urban center because of the building-barrier effect during both daytime and nighttime weak-UHI (<1.25°C) periods. This produced a regional-normalized rainfall (NR) minimum in the urban center and directly downwind of the urban area (of up to −35%), with maximum values along its downwind lateral edges (of >15%). Strong UHIs (>1.25°C), however, induced or enhanced thunderstorm formation (again day and night), which produced an NR maximum in the most urbanized area of up to 75%.
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He, Jianming y Charles C. S. Song. "Evaluation of pedestrian winds in urban area by numerical approach". Journal of Wind Engineering and Industrial Aerodynamics 81, n.º 1-3 (mayo de 1999): 295–309. http://dx.doi.org/10.1016/s0167-6105(99)00025-2.
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Ratti, C., S. Di Sabatino y R. Britter. "Urban texture analysis with image processing techniques: winds and dispersion". Theoretical and Applied Climatology 84, n.º 1-3 (7 de octubre de 2005): 77–90. http://dx.doi.org/10.1007/s00704-005-0146-z.
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de Foy, B., A. Clappier, L. T. Molina y M. J. Molina. "Distinct wind convergence patterns in the Mexico City basin due to the interaction of the gap winds with the synoptic flow". Atmospheric Chemistry and Physics 6, n.º 5 (24 de abril de 2006): 1249–65. http://dx.doi.org/10.5194/acp-6-1249-2006.
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Abstract. Mexico City lies in a high altitude basin where air quality and pollutant fate is strongly influenced by local winds. The combination of high terrain with weak synoptic forcing leads to weak and variable winds with complex circulation patterns. A gap wind entering the basin in the afternoon leads to very different wind convergence lines over the city depending on the meteorological conditions. Surface and upper-air meteorological observations are analysed during the MCMA-2003 field campaign to establish the meteorological conditions and obtain an index of the strength and timing of the gap wind. A mesoscale meteorological model (MM5) is used in combination with high-resolution satellite data for the land surface parameters and soil moisture maps derived from diurnal ground temperature range. A simple method to map the lines of wind convergence both in the basin and on the regional scale is used to show the different convergence patterns according to episode types. The gap wind is found to occur on most days of the campaign and is the result of a temperature gradient across the southern basin rim which is very similar from day to day. Momentum mixing from winds aloft into the surface layer is much more variable and can determine both the strength of the flow and the pattern of the convergence zones. Northerly flows aloft lead to a weak jet with an east-west convergence line that progresses northwards in the late afternoon and early evening. Westerlies aloft lead to both stronger gap flows due to channelling and winds over the southern and western basin rim. This results in a north-south convergence line through the middle of the basin starting in the early afternoon. Improved understanding of basin meteorology will lead to better air quality forecasts for the city and better understanding of the chemical regimes in the urban atmosphere.
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Wang, Huanhuan, Eden Furtak-Cole y Keith Ngan. "Estimating Mean Wind Profiles Inside Realistic Urban Canopies". Atmosphere 14, n.º 1 (27 de diciembre de 2022): 50. http://dx.doi.org/10.3390/atmos14010050.
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Mean wind profiles within a unit-aspect-ratio street canyon have been estimated by solving the three-dimensional Poisson equation for a set of discrete vortex sheets. The validity of this approach, which assumes inviscid vortex dynamics away from boundaries and a small nonlinear contribution to the growth of turbulent fluctuations, is tested for a series of idealised and realistic flows. In this paper, the effects of urban geometry on accuracy are examined with neutral flow over shallow, deep, asymmetric and realistic canyons, while thermal effects are investigated for a single street canyon and both bottom cooling and heating. The estimated mean profiles of the streamwise and spanwise velocity components show good agreement with reference profiles obtained from the large-eddy simulation: the canyon-averaged errors (e.g., normalised absolute errors around 1%) are of the same order of magnitude as those for the unit-aspect-ratio street canyon. It is argued that the approach generalises to more realistic flows because strong spatial localisation of the vorticity field is preserved. This work may be applied to high-resolution modelling of winds and pollutants, for which mean wind profiles are required, and fast statistical modelling, for which physically-based estimates can serve as initial guesses or substitutes for analytical models.
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Reames, Larissa J. y David J. Stensrud. "Sensitivity of Simulated Urban–Atmosphere Interactions in Oklahoma City to Urban Parameterization". Journal of Applied Meteorology and Climatology 56, n.º 5 (mayo de 2017): 1405–30. http://dx.doi.org/10.1175/jamc-d-16-0223.1.
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AbstractThe world’s population is increasingly concentrated in large urban areas. Many observational and modeling studies have explored how these large, population-dense cities modify local and mesoscale atmospheric phenomena. These modeling studies often use an urban canopy model to parameterize urban surfaces. However, it is unclear whether this approach is appropriate for more suburban cities, such as those found in the Great Plains. Thus, the Weather Research and Forecasting Model was run for a week over Oklahoma City, Oklahoma, and results were compared with observations. Overall, four configurations were examined. Two simulations used the Noah LSM, one with all urban areas removed (CTRL), and the other with urban areas parameterized by a modified Noah land surface model with three urban categories (LSMMOD). Additional simulations utilized a single-layer urban canopy model (SLUCM) either with default urban fraction values (SLUCM1) or with urban fractions taken from the National Land Cover Database (SLUCM2). Results from the three urban runs compared favorably to high-density temperature observations of the urban heat island. The SLUCM1 run was the most realistic, although the urban fractions applied were the least representative of Oklahoma City. All urban runs also produced a drier and deeper planetary boundary layer over the city. The prediction of near-surface winds was most problematic, with the two SLUCM runs unable to correctly reproduce reduced wind speeds over the city. The modified Noah LSM provided best overall agreement with observations and represents a reasonable option for simulating the urban effects of more-suburban cities.
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Garuma, Gemechu Fanta. "How the Interaction of Heatwaves and Urban Heat Islands Amplify Urban Warming". Advances in Environmental and Engineering Research 3, n.º 2 (29 de marzo de 2022): 1. http://dx.doi.org/10.21926/aeer.2202022.
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An increase in global temperature will likely result in more intense and frequent heatwaves that would last longer. Simultaneously, the growth of urban population requires more areas of land incorporated into urbanization, because most people are expected to live in cities, which will increase the intensity and duration of urban heat islands. However, the extent of the link between global warming induced heatwaves and urbanization caused heat islands is barely understood. Understanding the link would give a new information about catastrophic heat mitigation strategies. This paper, therefore, quantifies, at the sub-continental scale of Eastern North America, the effects of background perturbations by the synergies between heatwaves and urban heat islands using simulations from the Weather Research and Forecasting (WRF) model, and focusing on the responses of urban energy balances, boundary layer height and vertical profiles of heat, momentum and moisture. Results showed that urban heat islands exacerbate heatwaves by deepening the turbulent boundary layer height, modifying the urban surface energy and regional winds. The fractional energy shift from latent to sensible heat fluxes and the consequent changes to the urban planetary boundary layer tends to amplify the intensity, extent and duration of extensive heatwaves. The response of ground heat fluxes to urban surfaces lags, while urban canopy humidity dissipates earlier because at the onset of the heatwave the surface water evaporates quickly to the point where there is less water left for evaporation leaving the urbanized regions vulnerable to more heating. During the heatwave event, the mean wind speed dropped by 2.5 m/s, hence less cool air is available for ventilation. The planetary boundary layer deepens by a maximum of 90-m over urban compared to rural and this may prolong urban surface heating. Based on the results, it can be concluded that the best heat-stress management strategies from the perspectives of urban energy balance and planetary boundary layer height is an integral approach that would lower sensible heat fluxes and increase surface albedo, latent heat fluxes and wind flows towards urban centers.
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Garuma, Gemechu Fanta. "How the Interaction of Heatwaves and Urban Heat Islands Amplify Urban Warming". Advances in Environmental and Engineering Research 3, n.º 2 (29 de marzo de 2022): 1. http://dx.doi.org/10.21926/aeer.2202022.
Texto completoResumen
An increase in global temperature will likely result in more intense and frequent heatwaves that would last longer. Simultaneously, the growth of urban population requires more areas of land incorporated into urbanization, because most people are expected to live in cities, which will increase the intensity and duration of urban heat islands. However, the extent of the link between global warming induced heatwaves and urbanization caused heat islands is barely understood. Understanding the link would give a new information about catastrophic heat mitigation strategies. This paper, therefore, quantifies, at the sub-continental scale of Eastern North America, the effects of background perturbations by the synergies between heatwaves and urban heat islands using simulations from the Weather Research and Forecasting (WRF) model, and focusing on the responses of urban energy balances, boundary layer height and vertical profiles of heat, momentum and moisture. Results showed that urban heat islands exacerbate heatwaves by deepening the turbulent boundary layer height, modifying the urban surface energy and regional winds. The fractional energy shift from latent to sensible heat fluxes and the consequent changes to the urban planetary boundary layer tends to amplify the intensity, extent and duration of extensive heatwaves. The response of ground heat fluxes to urban surfaces lags, while urban canopy humidity dissipates earlier because at the onset of the heatwave the surface water evaporates quickly to the point where there is less water left for evaporation leaving the urbanized regions vulnerable to more heating. During the heatwave event, the mean wind speed dropped by 2.5 m/s, hence less cool air is available for ventilation. The planetary boundary layer deepens by a maximum of 90-m over urban compared to rural and this may prolong urban surface heating. Based on the results, it can be concluded that the best heat-stress management strategies from the perspectives of urban energy balance and planetary boundary layer height is an integral approach that would lower sensible heat fluxes and increase surface albedo, latent heat fluxes and wind flows towards urban centers.
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Ryu, Young-Hee, Jong-Jin Baik y Sang-Hyun Lee. "A New Single-Layer Urban Canopy Model for Use in Mesoscale Atmospheric Models". Journal of Applied Meteorology and Climatology 50, n.º 9 (septiembre de 2011): 1773–94. http://dx.doi.org/10.1175/2011jamc2665.1.
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AbstractA new single-layer urban canopy model for use in mesoscale atmospheric models is developed and validated. The urban canopy model represents a built-up area as a street canyon, two facing buildings, and a road. In this model, the two facing walls are divided into sunlit and shaded walls on the basis of solar azimuth angle and canyon orientation, and individual surface temperature and energy budget are calculated for each wall. In addition, for better estimation of turbulent energy exchange within the canyon, a computational fluid dynamics model is employed to incorporate the effects of canyon aspect ratio (height-to-width ratio) and reference wind direction on canyon wind speed. The model contains the essential physical processes occurring in an urban canopy: absorption and reflection of shortwave and longwave radiation, exchanges of turbulent energy and water between surfaces (roof, two facing walls, and road) and adjacent air, and heat transfer by conduction through substrates. The developed urban canopy model is validated using datasets obtained at two urban sites: Marseille, France, and Basel, Switzerland. The model satisfactorily reproduces canyon air temperatures, surface temperatures, net radiation, sensible heat fluxes, latent heat fluxes, and storage heat fluxes for both sites. Extensive experiments are conducted to examine the sensitivities of the urban surface energy balance to meteorological factors and urban surface parameters. The reference wind speed is found to be a more crucial meteorological factor than the reference air temperature in altering urban surface energy balance, especially for weak winds. The urban surface energy balance is most sensitive to the roof albedo among urban surface parameters. The roof fraction, canyon aspect ratio, and ratio of roughness length for momentum to that for heat for the roof play important roles in altering urban surface energy balance.
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Huang, Tzu-Ling, Chien-Yuan Kuo, Chun-Ta Tzeng y Chi-Ming Lai. "The Influence of High-Rise Buildings on Pedestrian-Level Wind in Surrounding Street Canyons in an Urban Renewal Project". Energies 13, n.º 11 (30 de mayo de 2020): 2745. http://dx.doi.org/10.3390/en13112745.
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The pedestrian wind environment in a street canyon is affected by a multitude of factors, including the height and geometric shape of the surrounding buildings, the street width, the wind direction, and speed. Wind-tunnel tests were performed to determine the effects of constructing high buildings in an urban renewal project in New Taipei City, Taiwan on the pedestrian wind environments in the surrounding street canyons. The results show that replacing the original low-rise buildings with high-rise buildings could decrease the wind speed and natural ventilation potential in certain surrounding street canyons. The flow fields generated by approaching winds in various street canyons are highly complex in this practical case study. Thus, the pedestrian wind patterns in the street canyons cannot be interpreted in terms of channeling and shielding effects alone, as is typically reported in the literature.
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Burrows, Donald A., Eric A. Hendricks, Steve R. Diehl y Robert Keith. "Modeling Turbulent Flow in an Urban Central Business District". Journal of Applied Meteorology and Climatology 46, n.º 12 (1 de diciembre de 2007): 2147–64. http://dx.doi.org/10.1175/2006jamc1282.1.
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Abstract The Realistic Urban Spread and Transport of Intrusive Contaminants (RUSTIC) model has been developed as a simplified computational fluid dynamics model with a k–ω turbulence model to be used to provide moderately fast simulations of turbulent airflow in an urban environment. RUSTIC simulations were compared with wind tunnel measurements to refine and “calibrate” the parameters for the k–ω model. RUSTIC simulations were then run and compared with data from five different periods during the Joint Urban 2003 experiment. Predictions from RUSTIC were compared with data from 33 near-surface sonic anemometers as well as 8 sonic anemometers on a 90-m tower and a sodar wind profiler located in the Oklahoma City, Oklahoma, central business district. The data were subdivided into daytime and nighttime datasets and then the daytime data were further subdivided into exposed and sheltered sonic anemometers. While there was little difference between day and night for wind speed and direction comparisons, there was considerable difference for the turbulence kinetic energy (TKE) comparisons. In the nighttime cases, RUSTIC overpredicted the TKE but without any correlation between model and observations. On the other hand, for the daytime cases, RUSTIC underpredicted the TKE values and correlated well with the observations. RUSTIC predicted both winds and TKE much better for the exposed sonic anemometers than for the sheltered ones. For the 90-m tower location downwind of the central business district, RUSTIC predicted the vertical profile of wind speed and direction very closely but underestimated the TKE.