scholarly journals The impact of Los Angeles Basin pollution and stratospheric intrusions on the surrounding San Gabriel Mountains as seen by surface measurements, lidar, and numerical models

2021 ◽  
Vol 21 (8) ◽  
pp. 6129-6153
Author(s):  
Fernando Chouza ◽  
Thierry Leblanc ◽  
Mark Brewer ◽  
Patrick Wang ◽  
Sabino Piazzolla ◽  
...  
Keyword(s):  
Los Angeles ◽  
Wind Direction ◽  
Surface Ozone ◽  
Pollution Transport ◽  
Los Angeles Basin ◽  
San Gabriel Mountains ◽  
Lidar Measurements ◽  
The Impact ◽  
Stratospheric Intrusions ◽  
Ozone Levels

Abstract. In this work, the impact of Los Angeles Basin pollution transport and stratospheric intrusions on the surface ozone levels observed in the San Gabriel Mountains is investigated based on a combination of surface and lidar measurements as well as WRF-Chem (Weather Research and Forecasting with Chemistry) and WACCM (Whole Atmosphere Community Climate Model) runs. The number of days with observed surface ozone levels exceeding the National Ambient Air Quality Standards exhibit a clear seasonal pattern, with a maximum during summer, when models suggest a minimum influence of stratospheric intrusions and the largest impact from Los Angeles Basin pollution transport. Additionally, measured and modeled surface ozone and PM10 were analyzed as a function of season, time of the day, and wind direction. Measurements and models are in good qualitative agreement, with maximum surface ozone observed for southwest and west winds. For the prevailing summer wind direction, slightly south of the ozone maximum and corresponding to south-southwest winds, lower ozone levels were observed. Back trajectories suggest that this is associated with transport from the central Los Angeles Basin, where titration limits the amount of surface ozone. A quantitative comparison of the lidar profiles with WRF-Chem and WACCM models revealed good agreement near the surface, with models showing an increasing positive bias as function of altitude, reaching 75 % at 15 km above sea level. Finally, three selected case studies covering the different mechanisms affecting the near-surface ozone concentration over the San Gabriel Mountains, namely stratospheric intrusions and pollution transport, are analyzed based on surface and ozone lidar measurements, as well as co-located ceilometer measurements and models.

scholarly journals The impact of Los Angeles basin pollution and stratospheric intrusions on the surrounding San Gabriel Mountains as seen by surface measurements, lidar, and numerical models

2020 ◽  
Author(s):  
Fernando Chouza ◽  
Thierry Leblanc ◽  
Mark Brewer ◽  
Patrick Wang ◽  
Sabino Piazzolla ◽  
...  
Keyword(s):  
Los Angeles ◽  
Surface Ozone ◽  
Pollution Transport ◽  
Los Angeles Basin ◽  
San Gabriel Mountains ◽  
South West ◽  
Lidar Measurements ◽  
The Impact ◽  
Stratospheric Intrusions ◽  
Ozone Levels

Abstract. In this work, the impact of Los Angeles basin pollution transport and stratospheric intrusions on the surface ozone levels observed in the San Gabriel Mountains is investigated based on a combination of surface and lidar measurements as well as WRF-Chem (Weather Research and Forecasting with Chemistry) and WACCM (Whole Atmosphere Community Climate Model) model runs. The number of days with observed surface ozone levels exceeding the National Ambient Air Quality Standards exhibit a clear seasonal pattern, with a maximum during summer, when models suggest a minimum influence of stratospheric intrusions and the largest impact from Los Angeles basin pollution transport. Additionally, measured and modeled surface ozone and PM10 were analyzed as a function of season, time of the day and wind direction. Measurements and models are in good qualitative agreement, with maximum surface ozone observed for south-west and west winds. For the prevailing summer wind direction, slightly south of the ozone maximum and corresponding to south south-west winds, lower ozone levels were observed. Back-trajectories suggest that this is associated with transport from the central Los Angeles basin, where titration limits the amount of surface ozone. A quantitative comparison of the lidar profiles with WRF-Chem and WACCM models revealed good agreement near the surface, with models showing an increasing positive bias as function of altitude, reaching 75 % at 15 km above sea level. Finally, three selected case studies covering the different mechanisms affecting the near-surface ozone concentration over the San Gabriel mountains, namely stratospheric intrusions and pollution transport, are analyzed based on surface and ozone lidar measurements, as well as co-located ceilometer measurements and models.

scholarly journals Impacts of the 2020 COVID-19 Shutdown Measures on Ozone Production in the Los Angeles Basin

2020 ◽  
Author(s):  
Cesunica Ivey ◽  
Ziqi Gao ◽  
Khanh Do ◽  
Arash Kashfi Yeganeh ◽  
Armistead Russell ◽  
...  
Keyword(s):  
Los Angeles ◽  
Ozone Concentration ◽  
South Coast ◽  
Pollutant Emissions ◽  
Ozone Production ◽  
The South ◽  
Los Angeles Basin ◽  
Time Period ◽  
South Coast Air Basin ◽  
The Impact

In March and April 2020, the South Coast Air Basin of California (USA) experienced noticeable declines in on-road activity and primary traffic-related pollutant emissions. However, secondary ozone concentration trends were not consistent across the basin. This research letter explores the impact of meteorology and emissions during this time period. The study elucidates the potential impacts on ozone nonattainment status for the region.

scholarly journals Impact of forest fires, biogenic emissions and high temperatures on the elevated Eastern Mediterranean ozone levels during the hot summer of 2007

2012 ◽  
Vol 12 (18) ◽  
pp. 8727-8750 ◽  
Author(s):  
Ø. Hodnebrog ◽  
S. Solberg ◽  
F. Stordal ◽  
T. M. Svendby ◽  
D. Simpson ◽  
...  
Keyword(s):  
High Temperatures ◽  
Forest Fire ◽  
Forest Fires ◽  
Dry Deposition ◽  
Heat Waves ◽  
Surface Ozone ◽  
Biogenic Emissions ◽  
Fire Emissions ◽  
The Impact ◽  
Ozone Levels

Abstract. The hot summer of 2007 in southeast Europe has been studied using two regional atmospheric chemistry models; WRF-Chem and EMEP MSC-W. The region was struck by three heat waves and a number of forest fire episodes, greatly affecting air pollution levels. We have focused on ozone and its precursors using state-of-the-art inventories for anthropogenic, biogenic and forest fire emissions. The models have been evaluated against measurement data, and processes leading to ozone formation have been quantified. Heat wave episodes are projected to occur more frequently in a future climate, and therefore this study also makes a contribution to climate change impact research. The plume from the Greek forest fires in August 2007 is clearly seen in satellite observations of CO and NO2 columns, showing extreme levels of CO in and downwind of the fires. Model simulations reflect the location and influence of the fires relatively well, but the modelled magnitude of CO in the plume core is too low. Most likely, this is caused by underestimation of CO in the emission inventories, suggesting that the CO/NOx ratios of fire emissions should be re-assessed. Moreover, higher maximum values are seen in WRF-Chem than in EMEP MSC-W, presumably due to differences in plume rise altitudes as the first model emits a larger fraction of the fire emissions in the lowermost model layer. The model results are also in fairly good agreement with surface ozone measurements. Biogenic VOC emissions reacting with anthropogenic NOx emissions are calculated to contribute significantly to the levels of ozone in the region, but the magnitude and geographical distribution depend strongly on the model and biogenic emission module used. During the July and August heat waves, ozone levels increased substantially due to a combination of forest fire emissions and the effect of high temperatures. We found that the largest temperature impact on ozone was through the temperature dependence of the biogenic emissions, closely followed by the effect of reduced dry deposition caused by closing of the plants' stomata at very high temperatures. The impact of high temperatures on the ozone chemistry was much lower. The results suggest that forest fire emissions, and the temperature effect on biogenic emissions and dry deposition, will potentially lead to substantial ozone increases in a warmer climate.

scholarly journals Emission factor ratios, SOA mass yields, and the impact of vehicular emissions on SOA formation

2014 ◽  
Vol 14 (5) ◽  
pp. 2383-2397 ◽  
Author(s):  
J. J. Ensberg ◽  
P. L. Hayes ◽  
J. L. Jimenez ◽  
J. B. Gilman ◽  
W. C. Kuster ◽  
...  
Keyword(s):  
Los Angeles ◽  
Urban Areas ◽  
Organic Aerosol ◽  
Vehicular Emissions ◽  
Los Angeles Basin ◽  
Relative Contribution ◽  
Chamber Studies ◽  
Using Data ◽  
Factor Ratios ◽  
The Impact

Abstract. The underprediction of ambient secondary organic aerosol (SOA) levels by current atmospheric models in urban areas is well established, yet the cause of this underprediction remains elusive. Likewise, the relative contribution of emissions from gasoline- and diesel-fueled vehicles to the formation of SOA is generally unresolved. We investigate the source of these two discrepancies using data from the 2010 CalNex experiment carried out in the Los Angeles Basin (Ryerson et al., 2013). Specifically, we use gas-phase organic mass (GPOM) and CO emission factors in conjunction with measured enhancements in oxygenated organic aerosol (OOA) relative to CO to quantify the significant lack of closure between expected and observed organic aerosol concentrations attributable to fossil-fuel emissions. Two possible conclusions emerge from the analysis to yield consistency with the ambient data: (1) vehicular emissions are not a dominant source of anthropogenic fossil SOA in the Los Angeles Basin, or (2) the ambient SOA mass yields used to determine the SOA formation potential of vehicular emissions are substantially higher than those derived from laboratory chamber studies.

scholarly journals Emission factor ratios, SOA mass yields, and the impact of vehicular emissions on SOA formation

2013 ◽  
Vol 13 (10) ◽  
pp. 27779-27810 ◽  
Author(s):  
J. J. Ensberg ◽  
P. L. Hayes ◽  
J. L. Jimenez ◽  
J. B. Gilman ◽  
W. C. Kuster ◽  
...  
Keyword(s):  
Los Angeles ◽  
Urban Areas ◽  
Organic Aerosol ◽  
Diesel Emissions ◽  
Vehicular Emissions ◽  
Aerosol Formation ◽  
Los Angeles Basin ◽  
Relative Contribution ◽  
Chamber Studies ◽  
The Impact

Abstract. The underprediction of ambient secondary organic aerosol (SOA) levels by atmospheric models in urban areas is well established, yet the cause of this underprediction remains elusive. Likewise, the relative contribution of emissions from gasoline- and diesel-fueled vehicles to the formation of SOA is generally unresolved. Here we address these two issues using data from the 2010 CalNex experiment carried out in the Los Angeles basin (Ryerson et al., 2013). We use gas-phase organic mass (GPOM) and CO emission factors in conjunction with measured enhancements in oxygenated organic aerosol (OOA) relative to CO to investigate the relative importance of gasoline vs. diesel emissions to organic aerosol formation. Two possible conclusions emerge from the analysis to yield consistency with the ambient data: (1) vehicular emissions are not a dominant source of anthropogenic fossil SOA in the Los Angeles basin, or (2) ambient SOA mass yields are substantially higher than those derived from laboratory chamber studies.

scholarly journals A model study of the Eastern Mediterranean ozone levels during the hot summer of 2007

2012 ◽  
Vol 12 (3) ◽  
pp. 7617-7675 ◽  
Author(s):  
Ø. Hodnebrog ◽  
S. Solberg ◽  
F. Stordal ◽  
T. M. Svendby ◽  
D. Simpson ◽  
...  
Keyword(s):  
High Temperatures ◽  
Forest Fire ◽  
Dry Deposition ◽  
Heat Waves ◽  
Surface Ozone ◽  
Biogenic Emissions ◽  
Climate Change Research ◽  
Fire Emissions ◽  
The Impact ◽  
Ozone Levels

Abstract. The hot summer of 2007 in Southeast Europe has been studied using two regional atmospheric chemistry models; WRF-Chem and EMEP MSC-W. The region was struck by three heat waves and a number of forest fire episodes, greatly affecting air pollution levels. We have focused on ozone and its precursors using state-of-the-art inventories for anthropogenic, biogenic and forest fire emissions. The models have been evaluated against measurement data, and processes leading to ozone formation have been quantified. Heat wave episodes are projected to occur more frequently in a future climate, and therefore this study also makes a contribution to climate change research. The plume from the Greek forest fires in August 2007 is clearly seen in satellite observations of CO and NO2 columns, showing extreme levels of CO in and downwind of the fires. Model simulations reflect the location and influence of the fires relatively well, but the modelled magnitude of CO in the plume core is too low. Most likely, this is caused by underestimation of CO in the emission inventories, suggesting that the CO/NOx ratios of fire emissions should be re-assessed. Moreover, higher maximum values are seen in WRF-Chem than in EMEP MSC-W, presumably due to differences in plume rise altitudes as the first model emits a larger fraction of the fire emissions in the lowermost model layer. The model results are also in fairly good agreement with surface ozone measurements. Biogenic VOC emissions reacting with anthropogenic NOx emissions are calculated to contribute significantly to the levels of ozone in the region, but the magnitude and geographical distribution depend strongly on the model and biogenic emission module used. During the July and August heat waves, ozone levels increased substantially due to a combination of forest fire emissions and the effect of high temperatures. We found that the largest temperature impact on ozone was through the temperature dependence of the biogenic emissions, closely followed by the effect of decreased dry deposition. The impact of high temperatures on the ozone chemistry was much lower. The results suggest that forest fire emissions, and the temperature effect on biogenic emissions and dry deposition, will potentially lead to substantial ozone increases in a warmer climate.

scholarly journals Impacts of the 2020 COVID-19 Shutdown Measures on Ozone Production in the Los Angeles Basin

2020 ◽  
Author(s):  
Cesunica Ivey ◽  
Ziqi Gao ◽  
Khanh Do ◽  
Arash Kashfi Yeganeh ◽  
Armistead Russell ◽  
...  
Keyword(s):  
Los Angeles ◽  
Ozone Concentration ◽  
South Coast ◽  
Pollutant Emissions ◽  
Ozone Production ◽  
The South ◽  
Los Angeles Basin ◽  
Time Period ◽  
South Coast Air Basin ◽  
The Impact

In March and April 2020, the South Coast Air Basin of California (USA) experienced noticeable declines in on-road activity and primary traffic-related pollutant emissions. However, secondary ozone concentration trends were not consistent across the basin. This research letter explores the impact of meteorology and emissions during this time period. The study elucidates the potential impacts on ozone nonattainment status for the region.

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