scholarly journals Street-in-Grid modeling of gas-phase pollutants in Paris city

2019 ◽  
Author(s):  
Lya Lugon ◽  
Karine Sartelet ◽  
Youngseob Kim ◽  
Jérémy Vigneron ◽  
Olivier Chrétien
Keyword(s):  
Transport Model ◽  
Regional Scale ◽  
Chemical Transport ◽  
Scale Model ◽  
Background Concentrations ◽  
Chemical Transport Model ◽  
Time Step ◽  
Multi Scale ◽  
Pollutant Concentrations ◽  
Stationary Approach

Abstract. Regional-scale chemistry-transport models have coarse spatial resolution, and thus can only simulate background concentrations. They fail to simulate the high concentrations observed close to roads and in streets, i.e. where a large part of the urban population lives. Local-scale models may be used to simulate concentrations in streets. They often assume that background concentrations are constant and/or use simplified chemistry. Recently developed, the multi-scale model Street-in-Grid (SinG) estimates gaseous pollutant concentrations simultaneously at local and regional scales, coupling them dynamically. This coupling combines the regional-scale chemistry-transport model Polair3D and the street network model MUNICH (Model of Urban Network of Intersecting Canyons and Highway). MUNICH models explicitly street canyons and intersections, and it is coupled to the first vertical level of the chemical-transport model, enabling the transfer of pollutant mass between the street canyon roof and the atmosphere. The original versions of SinG and MUNICH adopt a stationary hypothesis to estimate pollutant concentrations in streets. Although the computation of NOx concentration is numerically stable with the stationary approach, the partitioning between NO and NO2 is highly dependent on the time step of coupling between transport and chemistry processes. In this study, a new non-stationary approach is presented with a fine coupling between transport and chemistry, leading to numerically stable partitioning between NO and NO2. Simulations of NO, NO2 and NOx concentrations over Paris city with SinG, MUNICH and Polair3D are compared to observations at traffic and urban stations to estimate the added value of multi-scale modeling with a dynamical coupling between the regional and local scales. As expected, the regional chemical-transport model underestimates NO and NO2 concentrations in the streets. However, there is a good agreement between the measurements and the concentrations simulated with MUNICH and SinG. The dynamic coupling between the local and regional scales tends to be important for streets with an intermediate aspect ratio and with high traffic emissions.

scholarly journals Nonstationary modeling of NO<sub>2</sub>, NO and NO<sub><i>x</i></sub> in Paris using the Street-in-Grid model: coupling local and regional scales with a two-way dynamic approach

2020 ◽  
Vol 20 (13) ◽  
pp. 7717-7740
Author(s):  
Lya Lugon ◽  
Karine Sartelet ◽  
Youngseob Kim ◽  
Jérémy Vigneron ◽  
Olivier Chrétien
Keyword(s):  
Transport Model ◽  
Regional Scale ◽  
Chemical Transport ◽  
Added Value ◽  
Scale Model ◽  
Background Concentrations ◽  
Chemical Transport Model ◽  
Time Step ◽  
Multi Scale ◽  
Pollutant Concentrations

Abstract. Regional-scale chemistry-transport models have coarse spatial resolution (coarser than 1 km ×1 km) and can thus only simulate background concentrations. They fail to simulate the high concentrations observed close to roads and in streets, where a large part of the urban population lives. Local-scale models may be used to simulate concentrations in streets. They often assume that background concentrations are constant and/or use simplified chemistry. Recently developed, the multi-scale model Street-in-Grid (SinG) estimates gaseous pollutant concentrations simultaneously at local and regional scales by coupling them dynamically. This coupling combines the regional-scale chemistry-transport model Polair3D and a street-network model, the Model of Urban Network of Intersecting Canyons and Highway (MUNICH), with a two-way feedback. MUNICH explicitly models street canyons and intersections, and it is coupled to the first vertical level of the chemical-transport model, enabling the transfer of pollutant mass between the street-canyon roof and the atmosphere. The original versions of SinG and MUNICH adopt a stationary hypothesis to estimate pollutant concentrations in streets. Although the computation of the NOx concentration is numerically stable with the stationary approach, the partitioning between NO and NO2 is highly dependent on the time step of coupling between transport and chemistry processes. In this study, a new nonstationary approach is presented with a fine coupling between transport and chemistry, leading to numerically stable partitioning between NO and NO2. Simulations of NO, NO2 and NOx concentrations over Paris with SinG, MUNICH and Polair3D are compared to observations at traffic and urban stations to estimate the added value of multi-scale modeling with a two-way dynamical coupling between the regional and local scales. As expected, the regional chemical-transport model underestimates NO and NO2 concentrations in the streets. However, there is good agreement between the measurements and the concentrations simulated with MUNICH and SinG. The two-way dynamic coupling between the local and regional scales tends to be important for streets with an intermediate aspect ratio and with high traffic emissions.

scholarly journals The chemical transport model Oslo CTM3

2012 ◽  
Vol 5 (2) ◽  
pp. 1561-1626 ◽  
Author(s):  
O. A. Søvde ◽  
M. J. Prather ◽  
I. S. A. Isaksen ◽  
T. K. Berntsen ◽  
F. Stordal ◽  
...  
Keyword(s):  
Large Scale ◽  
Transport Model ◽  
Chemical Transport ◽  
Horizontal Distribution ◽  
Chemical Transport Model ◽  
Polar Cap ◽  
Time Step ◽  
Transport Time ◽  
Photolysis Rates ◽  
Vertical Distributions

Abstract. We present here the global chemical transport model Oslo CTM3, an update of the Oslo CTM2. The update comprises a faster transport scheme, an improved wet scavenging scheme for large scale rain, updated photolysis rates and a new lightning parameterization. Oslo CTM3 is better parallelized and allows for stable, large time steps for advection, enabling more complex or high resolution simulations. Thorough comparisons between the Oslo CTM3, Oslo CTM2 and measurements are performed, and in general the Oslo CTM3 is found to reproduce measurements well. Inclusion of tropospheric sulfur chemistry and nitrate aerosols in CTM3 is shown to be important to reproduce tropospheric O3, OH and the CH4 lifetime well. Using the same meteorology to drive the two models, shows that some features related to transport are better resolved by the CTM3, such as polar cap transport, while features like transport close to the vortex edge are resolved better in the Oslo CTM2 due to its required shorter transport time step. The longer transport time steps in CTM3 result in larger errors e.g. near the jets, and when necessary, this can be remedied by using a shorter time step. An additional, more accurate and time consuming, treatment of polar cap transport is presented, however, both perform acceptably. A new treatment of the horizontal distribution of lightning is presented and found to compare well with measurements. Vertical distributions of lighting are updated, and tested against the old vertical distribution. The new profiles are found to produce more NOx in the tropical middle troposphere, and less at the surface and at high altitudes.

scholarly journals Atmospheric ethanol in London and the potential impacts of future fuel formulations

2016 ◽  
Vol 189 ◽  
pp. 105-120 ◽  
Author(s):  
Rachel E. Dunmore ◽  
Lisa K. Whalley ◽  
Tomás Sherwen ◽  
Mathew J. Evans ◽  
Dwayne E. Heard ◽  
...  
Keyword(s):  
Transport Model ◽  
Regional Scale ◽  
Road Transport ◽  
Emission Source ◽  
Chemical Mechanism ◽  
Scale Model ◽  
Chemical Transport Model ◽  
Regional Modelling ◽  
Primary Emissions ◽  
The Impact

There is growing global consumption of non-fossil fuels such as ethanol made from renewable biomass. Previous studies have shown that one of the main air quality disadvantages of using ethanol blended fuels is a significant increase in the production of acetaldehyde, an unregulated and toxic pollutant. Most studies on the impacts of ethanol blended gasoline have been carried out in the US and Brazil, with much less focus on the UK and Europe. We report time resolved measurements of ethanol in London during the winter and summer of 2012. In both seasons the mean mixing ratio of ethanol was around 5 ppb, with maximum values over 30 ppb, making ethanol currently the most abundant VOC in London air. We identify a road transport related source, with ‘rush-hour’ peaks observed. Ethanol is strongly correlated with other road transport-related emissions, such as small aromatics and light alkanes, and has no relationship to summer biogenic emissions. To determine the impact of road transport-related ethanol emission on secondary species (i.e. acetaldehyde and ozone), we use both a chemically detailed box model (incorporating the Master Chemical Mechanism, MCM) and a global and nested regional scale chemical transport model (GEOS-Chem), on various processing time scales. Using the MCM model, only 16% of the modelled acetaldehyde was formed from ethanol oxidation. However, the model significantly underpredicts the total levels of acetaldehyde, indicating a missing primary emission source, that appears to be traffic-related. Further support for a primary emission source comes from the regional scale model simulations, where the observed concentrations of ethanol and acetaldehyde can only be reconciled with the inclusion of large primary emissions. Although only constrained by one set of observations, the regional modelling suggests a European ethanol source similar in magnitude to that of ethane (∼60 Gg per year) and greater than that of acetaldehyde (∼10 Gg per year). The increased concentrations of ethanol and acetaldehyde from primary emissions impacts both radical and NOx cycling over Europe, resulting in significant regional impacts on NOy speciation and O3 concentrations, with potential changes to human exposure to air pollutants.

scholarly journals Development of an aerosol chemical transport model RAQM2 and predictions of Northeast Asian aerosol mass, size, chemistry, and mixing type

2012 ◽  
Vol 12 (5) ◽  
pp. 13405-13456 ◽  
Author(s):  
M. Kajino ◽  
Y. Inomata ◽  
K. Sato ◽  
H. Ueda ◽  
Z. Han ◽  
...  
Keyword(s):  
Air Quality ◽  
Transport Model ◽  
Regional Scale ◽  
Chemical Transport ◽  
Sea Salt ◽  
Chemical Components ◽  
Air Quality Model ◽  
Chemical Transport Model ◽  
Wide Range ◽  
Northeast Asian

Abstract. A new aerosol chemical transport model, Regional Air Quality Model 2 (RAQM2), was developed to simulate Asian air quality. We implemented a simple version of a modal-moment aerosol dynamics model (MADMS) and achieved a completely dynamic (non-equilibrium) solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super μm. To consider a variety of atmospheric aerosol properties, a category approach was utilized, in which the aerosols were distributed into 4 categories: Aitken mode (ATK), soot-free accumulation mode (ACM), soot aggregates (AGR), and coarse mode (COR). Condensation, evaporation, and Brownian coagulations for each category were solved dynamically. A regional-scale simulation (Δ x = 60 km) was performed for the entire year of 2006 covering the Northeast Asian region. Statistical analyses showed that the model reproduced the regional-scale transport and transformation of the major inorganic anthropogenic and natural air constituents within factors of 2 to 5. The modeled PM1/bulk ratios of the chemical components were consistent with the observations, indicating that the simulations of aerosol mixing types were successful. Non-sea salt SO42- mixed with ATK + ACM was the largest at Hedo in summer, whereas it mixed with AGR was substantial in cold seasons. Ninety-eight percent of the modeled NO3- was mixed with sea salt at Hedo, whereas 53.7% of the NO3- was mixed with sea salt at Gosan, located upwind toward the Asian continent. The condensation of HNO3 onto sea salt particles during transport over the ocean makes the difference in the NO3- mixing type at the two sites. Because the aerosol mixing type alters optical properties and cloud condensation nuclei activity, its accurate prediction and evaluation are indispensable for aerosol-cloud-radiation interaction studies.

scholarly journals Development of the RAQM2 aerosol chemical transport model and predictions of the Northeast Asian aerosol mass, size, chemistry, and mixing type

2012 ◽  
Vol 12 (24) ◽  
pp. 11833-11856 ◽  
Author(s):  
M. Kajino ◽  
Y. Inomata ◽  
K. Sato ◽  
H. Ueda ◽  
Z. Han ◽  
...  
Keyword(s):  
Air Quality ◽  
Transport Model ◽  
Regional Scale ◽  
Chemical Transport ◽  
Sea Salt ◽  
Aerosol Size Distribution ◽  
Chemical Components ◽  
Chemical Transport Model ◽  
Wide Range ◽  
Northeast Asian

Abstract. A new aerosol chemical transport model, the Regional Air Quality Model 2 (RAQM2), was developed to simulate the Asian air quality. We implemented a simple version of a triple-moment modal aerosol dynamics model (MADMS) and achieved a completely dynamic (non-equilibrium) solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super-μm. To consider a variety of atmospheric aerosol properties, a category approach was utilized in which the aerosols were distributed into four categories: particles in the Aitken mode (ATK), soot-free particles in the accumulation mode (ACM), soot aggregates (AGR), and particles in the coarse mode (COR). The aerosol size distribution in each category is characterized by a single mode. The condensation, evaporation, and Brownian coagulations for each mode were solved dynamically. A regional-scale simulation (Δx = 60 km) was performed for the entire year of 2006 covering the Northeast Asian region. The modeled PM1/bulk ratios of the chemical components were consistent with observations, indicating that the simulated aerosol mixing types were consistent with those in nature. The non–sea-salt SO42− mixed with ATK + ACM was the largest at Hedo in summer, whereas the SOSO42− was substantially mixed with AGR in the cold seasons. Ninety-eight percent of the modeled NO3− was mixed with sea salt at Hedo, whereas 53.7% of the NO3− was mixed with sea salt at Gosan, which is located upwind toward the Asian continent. The condensation of HNO3 onto sea salt particles during transport over the ocean accounts for the difference in the NO3− mixing type at the two sites. Because the aerosol mixing type alters the optical properties and cloud condensation nuclei activity, its accurate prediction and evaluation are indispensable for aerosol-cloud-radiation interaction studies.

scholarly journals Modeling wet deposition and concentration of inorganics over Northeast Asia with MRI-PM/c

2012 ◽  
Vol 5 (6) ◽  
pp. 1363-1375 ◽  
Author(s):  
M. Kajino ◽  
M. Deushi ◽  
T. Maki ◽  
N. Oshima ◽  
Y. Inomata ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Wet Deposition ◽  
Climate Model ◽  
Transport Model ◽  
Regional Scale ◽  
Northeast Asia ◽  
Tropospheric Chemistry ◽  
Scale Model ◽  
Chemical Transport Model ◽  
Gaseous Species

Abstract. We conducted a regional-scale simulation over Northeast Asia for the year 2006 using an aerosol chemical transport model, with time-varying lateral and upper boundary concentrations of gaseous species predicted by a global stratospheric and tropospheric chemistry-climate model. The present one-way nested global-through-regional-scale model is named the Meteorological Research Institute–Passive-tracers Model system for atmospheric Chemistry (MRI-PM/c). We evaluated the model's performance with respect to the major anthropogenic and natural inorganic components, SO42−, NH4+, NO3−, Na+ and Ca2+ in the air, rain and snow measured at the Acid Deposition Monitoring Network in East Asia (EANET) stations. Statistical analysis showed that approximately 40–50 % and 70–80 % of simulated concentration and wet deposition of SO42−, NH4+, NO3−and Ca2+ are within factors of 2 and 5 of the observations, respectively. The prediction of the sea-salt originated component Na+ was not successful at near-coastal stations (where the distance from the coast ranged from 150 to 700 m), because the model grid resolution (Δx=60 km) is too coarse to resolve it. The simulated Na+ in precipitation was significantly underestimated by up to a factor of 30.

scholarly journals The chemical transport model Oslo CTM3

2012 ◽  
Vol 5 (6) ◽  
pp. 1441-1469 ◽  
Author(s):  
O. A. Søvde ◽  
M. J. Prather ◽  
I. S. A. Isaksen ◽  
T. K. Berntsen ◽  
F. Stordal ◽  
...  
Keyword(s):  
Large Scale ◽  
Transport Model ◽  
Chemical Transport ◽  
Horizontal Distribution ◽  
Small Scale ◽  
Chemical Transport Model ◽  
Polar Cap ◽  
Time Step ◽  
Transport Time ◽  
Fractional Cloud

Abstract. We present here the global chemical transport model Oslo CTM3, an update of the Oslo CTM2. The update comprises a faster transport scheme, an improved wet scavenging scheme for large scale rain, updated photolysis rates and a new lightning parameterization. Oslo CTM3 is better parallelized and allows for stable, large time steps for advection, enabling more complex or high spatial resolution simulations. A new treatment of the horizontal distribution of lightning is presented and found to compare well with measurements. The vertical distribution of lightning is updated and found to be a large contributor to CTM2–CTM3 differences, producing more NOx in the tropical middle troposphere, and less at the surface and at high altitudes. Compared with Oslo CTM2, Oslo CTM3 is faster, more capable and has better conceptual models for scavenging, vertical transport and fractional cloud cover. CTM3 captures stratospheric O3 better than CTM2, but shows minor improvements in terms of matching atmospheric observations in the troposphere. Use of the same meteorology to drive the two models shows that some features related to transport are better resolved by the CTM3, such as polar cap transport, while features like transport close to the vortex edge are resolved better in the Oslo CTM2 due to its required shorter transport time step. The longer transport time steps in CTM3 result in larger errors, e.g., near the jets, and when necessary the errors can be reduced by using a shorter time step. Using a time step of 30 min, the new transport scheme captures both large-scale and small-scale variability in atmospheric circulation and transport, with no loss of computational efficiency. We present a version of the new transport scheme which has been specifically tailored for polar studies, resulting in more accurate polar cap transport than the standard CTM3 transport, confirmed by comparison to satellite observations. Inclusion of tropospheric sulfur chemistry and nitrate aerosols in CTM3 is shown to be important to reproduce tropospheric O3, OH and the CH4 lifetime well.

scholarly journals Regional scale ozone data assimilation using an ensemble Kalman filter and the CHIMERE chemical transport model

2014 ◽  
Vol 7 (1) ◽  
pp. 283-302 ◽  
Author(s):  
B. Gaubert ◽  
A. Coman ◽  
G. Foret ◽  
F. Meleux ◽  
A. Ung ◽  
...  
Keyword(s):  
Kalman Filter ◽  
Data Assimilation ◽  
Ensemble Kalman Filter ◽  
Transport Model ◽  
Regional Scale ◽  
Chemical Transport ◽  
Quality Analysis ◽  
Observation Error ◽  
Chemical Transport Model ◽  
Sensitivity Tests

Abstract. An ensemble Kalman filter (EnKF) has been coupled to the CHIMERE chemical transport model in order to assimilate ozone ground-based measurements on a regional scale. The number of ensembles is reduced to 20, which allows for future operational use of the system for air quality analysis and forecast. Observation sites of the European ozone monitoring network have been classified using criteria on ozone temporal variability, based on previous work by Flemming et al. (2005). This leads to the choice of specific subsets of suburban, rural and remote sites for data assimilation and for evaluation of the reference run and the assimilation system. For a 10-day experiment during an ozone pollution event over Western Europe, data assimilation allows for a significant improvement in ozone fields: the RMSE is reduced by about a third with respect to the reference run, and the hourly correlation coefficient is increased from 0.75 to 0.87. Several sensitivity tests focus on an a posteriori diagnostic estimation of errors associated with the background estimate and with the spatial representativeness of observations. A strong diurnal cycle of both these errors with an amplitude up to a factor of 2 is made evident. Therefore, the hourly ozone background error and the observation error variances are corrected online in separate assimilation experiments. These adjusted background and observational error variances provide a better uncertainty estimate, as verified by using statistics based on the reduced centered random variable. Over the studied 10-day period the overall EnKF performance over evaluation stations is found relatively unaffected by different formulations of observation and simulation errors, probably due to the large density of observation sites. From these sensitivity tests, an optimal configuration was chosen for an assimilation experiment extended over a three-month summer period. It shows a similarly good performance as the 10-day experiment.

scholarly journals Urban Air Quality in a Coastal City: Wollongong during the MUMBA Campaign

Atmosphere ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 500 ◽  
Author(s):  
Clare Paton-Walsh ◽  
Élise-Andrée Guérette ◽  
Kathryn Emmerson ◽  
Martin Cope ◽  
Dagmar Kubistin ◽  
...  
Keyword(s):  
Air Quality ◽  
Transport Model ◽  
Regional Scale ◽  
Extreme Temperature ◽  
Performance Standards ◽  
Chemical Transport ◽  
Urban Air ◽  
Chemical Transport Model ◽  
Coastal City ◽  
The Impact

We present findings from the Measurements of Urban, Marine and Biogenic Air (MUMBA) campaign, which took place in the coastal city of Wollongong in New South Wales, Australia. We focus on a few key air quality indicators, along with a comparison to regional scale chemical transport model predictions at a spatial resolution of 1 km by 1 km. We find that the CSIRO chemical transport model provides accurate simulations of ozone concentrations at most times, but underestimates the ozone enhancements that occur during extreme temperature events. The model also meets previously published performance standards for fine particulate matter less than 2.5 microns in diameter (PM2.5), and the larger aerosol fraction (PM10). We explore the observed composition of the atmosphere within this urban air-shed during the MUMBA campaign and discuss the different influences on air quality in the city. Our findings suggest that further improvements to our ability to simulate air quality in this coastal city can be made through more accurate anthropogenic and biogenic emissions inventories and better understanding of the impact of extreme temperatures on air quality. The challenges in modelling air quality within the urban air-shed of Wollongong, including difficulties in accurate simulation of the local meteorology, are likely to be replicated in many other coastal cities in the Southern Hemisphere.

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