scholarly journals Impact of Bay-Breeze Circulations on Surface Air Quality and Boundary Layer Export

2014 ◽  
Vol 53 (7) ◽  
pp. 1697-1713 ◽  
Author(s):  
Christopher P. Loughner ◽  
Maria Tzortziou ◽  
Melanie Follette-Cook ◽  
Kenneth E. Pickering ◽  
Daniel Goldberg ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Chesapeake Bay ◽  
Surface Ozone ◽  
Early Morning ◽  
Pollution Transport ◽  
Air Quality Model ◽  
Quality Model ◽  
Early Afternoon ◽  
Bay Breeze

AbstractMeteorological and air-quality model simulations are analyzed alongside observations to investigate the role of the Chesapeake Bay breeze on surface air quality, pollutant transport, and boundary layer venting. A case study was conducted to understand why a particular day was the only one during an 11-day ship-based field campaign on which surface ozone was not elevated in concentration over the Chesapeake Bay relative to the closest upwind site and why high ozone concentrations were observed aloft by in situ aircraft observations. Results show that southerly winds during the overnight and early-morning hours prevented the advection of air pollutants from the Washington, D.C., and Baltimore, Maryland, metropolitan areas over the surface waters of the bay. A strong and prolonged bay breeze developed during the late morning and early afternoon along the western coastline of the bay. The strength and duration of the bay breeze allowed pollutants to converge, resulting in high concentrations locally near the bay-breeze front within the Baltimore metropolitan area, where they were then lofted to the top of the planetary boundary layer (PBL). Near the top of the PBL, these pollutants were horizontally advected to a region with lower PBL heights, resulting in pollution transport out of the boundary layer and into the free troposphere. This elevated layer of air pollution aloft was transported downwind into New England by early the following morning where it likely mixed down to the surface, affecting air quality as the boundary layer grew.

scholarly journals Transport analysis of ozone enhancement in Southern Ontario during BAQS-Met

2011 ◽  
Vol 11 (6) ◽  
pp. 2569-2583 ◽  
Author(s):  
H. He ◽  
D. W. Tarasick ◽  
W. K. Hocking ◽  
T. K. Carey-Smith ◽  
Y. Rochon ◽  
...  
Keyword(s):  
Air Quality ◽  
Numerical Models ◽  
Stratospheric Ozone ◽  
Weather Prediction ◽  
Surface Ozone ◽  
Air Quality Model ◽  
Quality Model ◽  
Stratospheric Intrusion ◽  
Continuous Surface ◽  
Consistent Picture

Abstract. Twice-daily ozonesondes were launched from Harrow, in southwestern Ontario, Canada, during the BAQS-Met (Border Air Quality and Meteorology Study) field campaign in June and July of 2007. A co-located radar windprofiler measured tropopause height continuously. These data, in combination with continuous surface ozone measurements and geo-statistical interpolation of satellite ozone observations, present a consistent picture and indicate that a number of significant ozone enhancements in the troposphere were observed that were the result of stratospheric intrusion events. The combined observations have also been compared with results from two Environment Canada numerical models, the operational weather prediction model GEM (as input to FLEXPART), and a new version of the regional air quality model AURAMS, in order to examine the ability of these models to accurately represent sporadic cross-tropopause ozone transport events. The models appear to reproduce intrusion events with some skill, implying that GEM dynamics (which also drive AURAMS) are able to represent such events well. There are important differences in the quantitative comparison, however; in particular, the poor vertical resolution of AURAMS around the tropopause causes it to bring down too much ozone in individual intrusions. These campaign results imply that stratospheric intrusions are important to the ozone budget of the mid-latitude troposphere, and appear to be responsible for much of the variability of ozone in the free troposphere. GEM-FLEXPART calculations indicate that stratospheric ozone intrusions contributed significantly to surface ozone on several occasions during the BAQS-Met campaign, and made a moderate but significant contribution to the overall tropospheric ozone budget.

scholarly journals Solar “brightening” impact on summer surface ozone between 1990 and 2010 in Europe – a model sensitivity study of the influence of the aerosol–radiation interactions

2018 ◽  
Vol 18 (13) ◽  
pp. 9741-9765 ◽  
Author(s):  
Emmanouil Oikonomakis ◽  
Sebnem Aksoyoglu ◽  
Martin Wild ◽  
Giancarlo Ciarelli ◽  
Urs Baltensperger ◽  
...  
Keyword(s):  
Air Quality ◽  
Surface Ozone ◽  
Biogenic Emissions ◽  
Base Case ◽  
Air Quality Model ◽  
Quality Model ◽  
Ozone Concentrations ◽  
Photolysis Rates ◽  
Ozone Trends ◽  
The Impact

Abstract. Surface solar radiation (SSR) observations have indicated an increasing trend in Europe since the mid-1980s, referred to as solar “brightening”. In this study, we used the regional air quality model, CAMx (Comprehensive Air Quality Model with Extensions) to simulate and quantify, with various sensitivity runs (where the year 2010 served as the base case), the effects of increased radiation between 1990 and 2010 on photolysis rates (with the PHOT1, PHOT2 and PHOT3 scenarios, which represented the radiation in 1990) and biogenic volatile organic compound (BVOC) emissions (with the BIO scenario, which represented the biogenic emissions in 1990), and their consequent impacts on summer surface ozone concentrations over Europe between 1990 and 2010. The PHOT1 and PHOT2 scenarios examined the effect of doubling and tripling the anthropogenic PM2.5 concentrations, respectively, while the PHOT3 investigated the impact of an increase in just the sulfate concentrations by a factor of 3.4 (as in 1990), applied only to the calculation of photolysis rates. In the BIO scenario, we reduced the 2010 SSR by 3 % (keeping plant cover and temperature the same), recalculated the biogenic emissions and repeated the base case simulations with the new biogenic emissions. The impact on photolysis rates for all three scenarios was an increase (in 2010 compared to 1990) of 3–6 % which resulted in daytime (10:00–18:00 Local Mean Time – LMT) mean surface ozone differences of 0.2–0.7 ppb (0.5–1.5 %), with the largest hourly difference rising as high as 4–8 ppb (10–16 %). The effect of changes in BVOC emissions on daytime mean surface ozone was much smaller (up to 0.08 ppb, ∼ 0.2 %), as isoprene and terpene (monoterpene and sesquiterpene) emissions increased only by 2.5–3 and 0.7 %, respectively. Overall, the impact of the SSR changes on surface ozone was greater via the effects on photolysis rates compared to the effects on BVOC emissions, and the sensitivity test of their combined impact (the combination of PHOT3 and BIO is denoted as the COMBO scenario) showed nearly additive effects. In addition, all the sensitivity runs were repeated on a second base case with increased NOx emissions to account for any potential underestimation of modeled ozone production; the results did not change significantly in magnitude, but the spatial coverage of the effects was profoundly extended. Finally, the role of the aerosol–radiation interaction (ARI) changes in the European summer surface ozone trends was suggested to be more important when comparing to the order of magnitude of the ozone trends instead of the total ozone concentrations, indicating a potential partial damping of the effects of ozone precursor emissions' reduction.

scholarly journals Error apportionment for atmospheric chemistry-transport models: a new approach to model evaluation

2016 ◽  
Author(s):  
E. Solazzo ◽  
S. Galmarini
Keyword(s):  
Air Quality ◽  
Correlation Coefficient ◽  
Atmospheric Chemistry ◽  
Model Evaluation ◽  
Surface Ozone ◽  
Model Complexity ◽  
Air Quality Model ◽  
Quality Model ◽  
Causes Of Errors ◽  
Bias Variance

Abstract. In this study, methods are proposed to diagnose the causes of errors in air quality (AQ) modelling systems. We investigate the deviation between modelled and observed time series of surface ozone through a revised formulation for breaking down the mean square error (MSE) into bias, variance, and the minimum achievable MSE (mMSE). The bias measures the accuracy and implies the existence of systematic errors and poor representation of data complexity, the variance measures the precision and provides an estimate of the variability of the modelling results in relation to the observed data, and the mMSE reflects unsystematic errors and provides a measure of the associativity between the modelled and the observed fields through the correlation coefficient. Each of the error components is analysed independently and apportioned to resolved process based on the corresponding timescale (long scale, synoptic, diurnal, and intra-day) and as a function of model complexity. The apportionment of the error is applied to the AQMEII (Air Quality Model Evaluation International Initiative) group of models, which embrace the majority of regional AQ modelling systems currently used in Europe and North America. The proposed technique has proven to be a compact estimator of the operational metrics commonly used for model evaluation (bias, variance, and correlation coefficient), and has the further benefit of apportioning the error to the originating timescale, thus allowing for a clearer diagnosis of the process that caused the error.

scholarly journals Low modeled ozone production suggests underestimation of precursor emissions (especially NO<sub><i>x</i></sub>) in Europe

2018 ◽  
Vol 18 (3) ◽  
pp. 2175-2198 ◽  
Author(s):  
Emmanouil Oikonomakis ◽  
Sebnem Aksoyoglu ◽  
Giancarlo Ciarelli ◽  
Urs Baltensperger ◽  
André Stephan Henry Prévôt
Keyword(s):  
Air Quality ◽  
Surface Ozone ◽  
Model Performance ◽  
Ozone Production ◽  
Nox Emissions ◽  
Air Quality Model ◽  
Quality Model ◽  
Voc Emissions ◽  
Mixing Ratios ◽  
The Impact

Abstract. High surface ozone concentrations, which usually occur when photochemical ozone production takes place, pose a great risk to human health and vegetation. Air quality models are often used by policy makers as tools for the development of ozone mitigation strategies. However, the modeled ozone production is often not or not enough evaluated in many ozone modeling studies. The focus of this work is to evaluate the modeled ozone production in Europe indirectly, with the use of the ozone–temperature correlation for the summer of 2010 and to analyze its sensitivity to precursor emissions and meteorology by using the regional air quality model, the Comprehensive Air Quality Model with Extensions (CAMx). The results show that the model significantly underestimates the observed high afternoon surface ozone mixing ratios (≥ 60 ppb) by 10–20 ppb and overestimates the lower ones (< 40 ppb) by 5–15 ppb, resulting in a misleading good agreement with the observations for average ozone. The model also underestimates the ozone–temperature regression slope by about a factor of 2 for most of the measurement stations. To investigate the impact of emissions, four scenarios were tested: (i) increased volatile organic compound (VOC) emissions by a factor of 1.5 and 2 for the anthropogenic and biogenic VOC emissions, respectively, (ii) increased nitrogen oxide (NOx) emissions by a factor of 2, (iii) a combination of the first two scenarios and (iv) increased traffic-only NOx emissions by a factor of 4. For southern, eastern, and central (except the Benelux area) Europe, doubling NOx emissions seems to be the most efficient scenario to reduce the underestimation of the observed high ozone mixing ratios without significant degradation of the model performance for the lower ozone mixing ratios. The model performance for ozone–temperature correlation is also better when NOx emissions are doubled. In the Benelux area, however, the third scenario (where both NOx and VOC emissions are increased) leads to a better model performance. Although increasing only the traffic NOx emissions by a factor of 4 gave very similar results to the doubling of all NOx emissions, the first scenario is more consistent with the uncertainties reported by other studies than the latter, suggesting that high uncertainties in NOx emissions might originate mainly from the road-transport sector rather than from other sectors. The impact of meteorology was examined with three sensitivity tests: (i) increased surface temperature by 4 ∘C, (ii) reduced wind speed by 50 % and (iii) doubled wind speed. The first two scenarios led to a consistent increase in all surface ozone mixing ratios, thus improving the model performance for the high ozone values but significantly degrading it for the low ozone values, while the third scenario had exactly the opposite effects. Overall, the modeled ozone is predicted to be more sensitive to its precursor emissions (especially traffic NOx) and therefore their uncertainties, which seem to be responsible for the model underestimation of the observed high ozone mixing ratios and ozone production.

scholarly journals Unraveling the complex local-scale flows influencing ozone patterns in the southern Great Lakes of North America

2010 ◽  
Vol 10 (22) ◽  
pp. 10895-10915 ◽  
Author(s):  
I. Levy ◽  
P. A. Makar ◽  
D. Sills ◽  
J. Zhang ◽  
K. L. Hayden ◽  
...  
Keyword(s):  
Air Quality ◽  
North America ◽  
Great Lakes ◽  
Lake Erie ◽  
Surface Ozone ◽  
Inversion Layer ◽  
Air Quality Model ◽  
Quality Model ◽  
Mixing Ratios ◽  
Ozone Levels

Abstract. This study examines the complexity of various processes influencing summertime ozone levels in the southern Great Lakes region of North America. Results from the Border Air Quality and Meteorology (BAQS-Met) field campaign in the summer of 2007 are examined with respect to land-lake differences and local meteorology using a large array of ground-based measurements, aircraft data, and simulation results from a high resolution (2.5 km) regional air-quality model, AURAMS. Analyses of average ozone mixing ratio from the entire BAQS-Met intensive campaign period support previous findings that ozone levels are higher over the southern Great Lakes than over the adjacent land. However, there is great heterogeneity in the spatial distribution of surface ozone over the lakes, particularly over Lake Erie during the day, with higher levels located over the southwestern end of the lake. Model results suggest that some of these increased ozone levels are due to local emission sources in large nearby urban centers. While an ozone reservoir layer is predicted by the AURAMS model over Lake Erie at night, the land-lake differences in ozone mixing ratios are most pronounced during the night in a shallow inversion layer of about 200 m above the surface. After sunrise, these differences have a limited effect on the total mass of ozone over the lakes and land during the day, though they do cause elevated ozone levels in the lake-breeze air in some locations. The model also predicts a mean vertical circulation during the day with an updraft over Detroit-Windsor and downdraft over Lake St. Clair, which transports ozone up to 1500 m above ground and results in high ozone over the lake. Oscillations in ground-level ozone mixing ratios were observed on several nights and at several ground monitoring sites, with amplitudes of up to 40 ppbv and time periods of 15–40 min. Several possible mechanisms for these oscillations are discussed, but a complete understanding of their causes is not possible given current data and knowledge.

scholarly journals Comparison of tropospheric NO<sub>2</sub> columns from MAX-DOAS retrievals and regional air quality model simulations

2017 ◽  
Author(s):  
Anne-Marlene Blechschmidt ◽  
Joaquim Arteta ◽  
Adriana Coman ◽  
Lyana Curier ◽  
Henk Eskes ◽  
...  
Keyword(s):  
Air Quality ◽  
Global Scale ◽  
Regional Model ◽  
Tropospheric Chemistry ◽  
Pollution Transport ◽  
Model Ensemble ◽  
Air Quality Model ◽  
Quality Model ◽  
Tropospheric No2 ◽  
Regional Air Quality

Abstract. Tropospheric NO2 is hazardous to human health and can lead to tropospheric ozone formation, eutrophication of ecosystems and acid rain production. It is therefore important to establish accurate data based on models and observations to understand and monitor tropospheric NO2 concentrations on a regional and global scale. In the present study, MAX-DOAS tropospheric NO2 column retrievals from four European measurement stations are compared to regional model ensemble simulations. The latter are based on regional air quality models which contribute to the European regional ensemble forecasts and reanalyses of the operational Copernicus Atmosphere Monitoring Service (CAMS). Compared to other observational data usually applied for regional model validation, MAX-DOAS data is closer to the regional model data in terms of horizontal and vertical resolution and measurements are available during daylight. In general, there is a good agreement between simulated and retrieved NO2 column values for individual MAX-DOAS measurements with correlations between 45 and 75 % for tropospheric NO2 VCDs, indicating that the model ensemble represents the emission and tropospheric chemistry of NOx (NO + NO2) well. Pollution transport towards the stations is on average well represented by the models. However, large differences are found for individual pollution plumes. Seasonal cycles are overestimated, weekly cycles are reproduced well and diurnal cycles poorly represented by the model ensemble. In particular, simulated morning rush hour peaks are not confirmed by MAX-DOAS retrievals. Our results demonstrate that a large number of validation points are available from MAX-DOAS measurements, which should therefore be used more extensively in future regional air quality modelling studies.

scholarly journals Impact of Urbanization on the Predictions of Urban Meteorology and Air Pollutants over Four Major North American Cities

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 969 ◽  
Author(s):  
Shuzhan Ren ◽  
Craig Stroud ◽  
Stephane Belair ◽  
Sylvie Leroyer ◽  
Rodrigo Munoz-Alpizar ◽  
...  
Keyword(s):  
Air Quality ◽  
North American ◽  
Air Pollutants ◽  
Model Simulation ◽  
Ground Level ◽  
Early Morning ◽  
Heat Fluxes ◽  
Air Quality Model ◽  
Quality Model ◽  
American Cities

The sensitivities of meteorological and chemical predictions to urban effects over four major North American cities are investigated using the high-resolution (2.5-km) Environment and Climate Change Canada’s air quality model with the Town Energy Balance (TEB) scheme. Comparisons between the model simulation results with and without the TEB effect show that urbanization has great impacts on surface heat fluxes, vertical diffusivity, air temperature, humidity, atmospheric boundary layer height, land-lake circulation, air pollutants concentrations and Air Quality Health Index. The impacts have strong diurnal variabilities, and are very different in summer and winter. While the diurnal variations of the impacts share some similarities over each city, the magnitudes can be very different. The underlying mechanisms of the impacts are investigated. The TEB impacts on the predictions of meteorological and air pollutants over Toronto are evaluated against ground-based observations. The results show that the TEB scheme leads to a great improvement in biases and root-mean-square deviations in temperature and humidity predictions in downtown, uptown and suburban areas in the early morning and nighttime. The scheme also leads to a big improvement of predictions of NOx, PM2.5 and ground-level ozone in the downtown, uptown and industrial areas in the early morning and nighttime.

scholarly journals Low modeled ozone production suggests underestimation of precursor emissions (especially NO<sub>x</sub>) in Europe

2017 ◽  
Author(s):  
Emmanouil Oikonomakis ◽  
Sebnem Aksoyoglu ◽  
Giancarlo Ciarelli ◽  
Urs Baltensperger ◽  
André S. H. Prévôt
Keyword(s):  
Air Quality ◽  
Surface Ozone ◽  
High Surface ◽  
Mitigation Strategies ◽  
Ozone Production ◽  
Air Quality Model ◽  
Quality Model ◽  
Mixing Ratios ◽  
Modelling Studies ◽  
Regional Air Quality

Abstract. High surface ozone concentrations, which usually occur when photochemical ozone production takes place, pose a great risk to human health and vegetation. Air quality models are often used by policy makers as tools for the development of ozone mitigation strategies. However, the modeled ozone production is often not or not enough evaluated in many ozone modelling studies. The focus of this work is to evaluate the modeled ozone production in Europe indirectly, with the use of the ozone–temperature correlation for the summer of 2010 and to analyze its sensitivity to precursor emissions and meteorology by using the regional air quality model, CAMx. The results show that the model significantly underestimates the observed high afternoon surface ozone mixing ratios (≥ 60 ppb) by 10–20 ppb and overestimates the lower ones (

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