Use of a new generation urban scale dispersion model to estimate the concentration of oxides of nitrogen and sulphur dioxide in a large urban area

1999 ◽  
Vol 235 (1-3) ◽  
pp. 277-291 ◽  
Author(s):  
B Owen ◽  
H.A Edmunds ◽  
D.J Carruthers ◽  
D.W Raper
Keyword(s):  
Urban Area ◽  
Sulphur Dioxide ◽  
Dispersion Model ◽  
Oxides Of Nitrogen ◽  
Large Urban Area ◽  
New Generation

scholarly journals Development of the city-scale chemistry transport model CityChem-EPISODE and its application to the city of Hamburg

2018 ◽  
Author(s):  
Matthias Karl
Keyword(s):  
Air Quality ◽  
Urban Area ◽  
Transport Model ◽  
Dispersion Model ◽  
Temporal Correlation ◽  
Urban Atmosphere ◽  
Aerosol Formation ◽  
Urban Background ◽  
New Model ◽  
The City

Abstract. This paper describes the City-scale Chemistry (CityChem) extension of the urban dispersion model EPISODE with the aim to enable chemistry/transport simulations of multiple reactive pollutants on urban scales. The new model is called CityChem-EPISODE. The primary focus is on the simulation of urban ozone concentrations. Ozone is produced in photochemical reaction cycles involving nitrogen oxides (NOx) and volatile organic compounds (VOC) emitted by various anthropogenic activities in the urban area. The performance of the new model was evaluated with a series of synthetic tests and with a first application to the air quality situation in the city of Hamburg, Germany. The model performs fairly well for ozone in terms of temporal correlation and bias at the air quality monitoring stations in Hamburg. In summer afternoons, when photochemical activity is highest, modelled median ozone at an inner-city urban background station was about 30 % lower than the observed median ozone. Inaccuracy of the computed photolysis frequency of nitrogen dioxide (NO2) is the most probable explanation for this. CityChem-EPISODE reproduces the spatial variation of annual mean NO2 concentrations between urban background, traffic and industrial stations. However, the temporal correlation between modelled and observed hourly NO2 concentrations is weak for some of the stations. For daily mean PM10, the performance of CityChem-EPISODE is moderate due to low temporal correlation. The low correlation is linked to uncertainties in the seasonal cycle of the anthropogenic particulate matter (PM) emissions within the urban area. Missing emissions from domestic heating might be an explanation for the too low modelled PM10 in winter months. Four areas of need for improvement have been identified: (1) dry and wet deposition fluxes; (2) treatment of photochemistry in the urban atmosphere; (3) formation of secondary inorganic aerosol (SIA); and (4) formation of biogenic and anthropogenic secondary organic aerosol (SOA). The inclusion of secondary aerosol formation will allow for a better sectorial attribution of observed PM levels. Envisaged applications of the CityChem-EPISODE model are urban air quality studies, environmental impact assessment, sensitivity analysis of sector-specific emission and the assessment of local and regional emission abatement policy options.

Enhanced Methodologies to Enumerate Persons Experiencing Homelessness in a Large Urban Area

2015 ◽  
Vol 39 (5) ◽  
pp. 480-500 ◽  
Author(s):  
Catherine L. Troisi ◽  
Ritalinda D’Andrea ◽  
Gary Grier ◽  
Stephen Williams
Keyword(s):  
Urban Area ◽  
Large Urban Area

Variability in Atmospheric Chlorofluorocarbons (CCl3F and CCl2F2) near a Large Urban Area:  Implications for Groundwater Dating

1998 ◽  
Vol 32 (16) ◽  
pp. 2377-2382 ◽  
Author(s):  
David T. Ho ◽  
Peter Schlosser ◽  
William M. Smethie ◽  
H. James Simpson
Keyword(s):  
Urban Area ◽  
Large Urban Area ◽  
Groundwater Dating

scholarly journals Numerical Tools Dedicated to Wind Engineering in Large Urban Area

2016 ◽  
Vol 04 (03) ◽  
pp. 22-29
Author(s):  
Li Wang ◽  
Sophie Puygrenier ◽  
Guillaume Caniot ◽  
Stéphane Sanquer ◽  
Didier Delaunay
Keyword(s):  
Urban Area ◽  
Wind Engineering ◽  
Large Urban Area ◽  
Numerical Tools

scholarly journals Attitudes of graduating Canadian urology residents on the job market: Is it getting better or are we just spinning our wheels?

2017 ◽  
Vol 12 (4) ◽  
pp. 104-9 ◽  
Author(s):  
Gregory W. Hosier ◽  
Naji J. Touma
Keyword(s):  
Urban Area ◽  
Response Rate ◽  
Large Urban Area ◽  
Job Market ◽  
Employment Opportunities ◽  
The Past ◽  
Agreement Score ◽  
Strongly Agree ◽  
Ideal Practice ◽  
The Ideal

Introduction: There has been increasing awareness of employment difficulties for physicians, especially surgeons, in Canada over the past few years. Our objective was to elucidate the attitudes and experiences of graduating Canadian urology residents in obtaining employment.Methods: We surveyed four separate cohorts of graduating urology residents in 2010, 2011, 2016, and 2017. Responses from the 2010 and 2011 cohorts were combined and compared to the combined results of the 2016 and 2017 cohorts. Mean Likert responses were compared using unpaired t-tests. An agreement score was created for those responding with “strongly agree” and “agree” on the Likert scale.Results: A total of 126 surveys were administered with a 100% response rate. The job market was rated as poor or very poor by 64.9% and 58.4% of graduates in 2010/2011 and 2016/2017, respectively (p=0.67). Lack of resources was identified as the biggest barrier to improved employment in both cohorts. Networking at meetings and staff urologists at their institution were the most important factors aiding employment identified by both cohorts. The ideal practice was academic or academically associated community practices in a large urban area, with 5‒10 partners for both cohorts.Conclusions: The majority of graduating urology residents viewed the job market as poor or very poor and this did not change over a six-year period. It is unclear how much personal preference for location and practice type drove the somewhat negative outlook of employment opportunities, as the majority of residents were seeking large urban, academic, or academically associated community practices in competitive locations.

scholarly journals High-resolution mapping of vehicle emissions of atmospheric pollutants based on large-scale, real-world traffic datasets

2019 ◽  
Author(s):  
Daoyuan Yang ◽  
Shaojun Zhang ◽  
Tianlin Niu ◽  
Yunjie Wang ◽  
Honglei Xu ◽  
...  
Keyword(s):  
Urban Area ◽  
Real World ◽  
Vehicle Emissions ◽  
Large Scale ◽  
Emission Inventory ◽  
Road Traffic ◽  
Dispersion Model ◽  
Traffic Monitoring ◽  
Atmospheric Pollutants ◽  
Link Model

Abstract. On-road vehicle emissions are a major contributor to elevated air pollution levels in populous metropolitan areas. We developed a link-level emissions inventory of vehicular pollutants, called EMBEV-Link, based on multiple datasets extracted from the extensive road traffic monitoring network that covers the entire municipality of Beijing, China (16 400 km2). We employed the EMBEV-Link model under various traffic scenarios to capture the significant variability in vehicle emissions, temporally and spatially, due to the real-world traffic dynamics and the traffic restrictions implemented by the local government. The results revealed high carbon monoxide (CO) and total hydrocarbon (THC) emissions in the urban area (i.e., within the Fifth Ring Road) and during rush hours, both associated with the passenger vehicle traffic. By contrast, considerable fractions of nitrogen oxides (NOX), fine particulate matter (PM2.5) and black carbon (BC) emissions were present beyond the urban area, as heavy-duty trucks (HDTs) were not allowed to drive through the urban area during daytime. The EMBEV-Link model indicates that non-local HDTs could for 29 % and 38 % of estimated total on-road emissions of NOX and PM2.5, which were ignored in previous conventional emission inventories. We further combined the EMBEV-Link emission inventory and a computationally efficient dispersion model, RapidAir®, to simulate vehicular NOX concentrations at fine resolutions (10 m × 10 m in the entire municipality and 1 m × 1 m in the hotspots). The simulated results indicated a close agreement with ground observations and captured sharp concentration gradients from line sources to ambient areas. During the nighttime when the HDT traffic restrictions are lifted, HDTs could be responsible for approximately 10 μg m−3 of NOX in the urban area. The uncertainties of conventional top-down allocation methods, which were widely used to enhance the spatial resolution of vehicle emissions, are also discussed by comparison with the EMBEV-Link emission inventory.

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