scholarly journals Spatio-Temporal Characteristics of Tropospheric Ozone and Its Precursors in Guangxi, South China

Atmosphere ◽  
2018 ◽  
Vol 9 (9) ◽  
pp. 355 ◽  
Author(s):  
Yapeng Wang ◽  
Chao Yu ◽  
Jinhua Tao ◽  
Zifeng Wang ◽  
Yidan Si ◽  
...  
Keyword(s):  
South China ◽  
Tropospheric Ozone ◽  
Monsoon Season ◽  
Seasonal Pattern ◽  
Surface Ozone ◽  
Monitoring Network ◽  
Back Trajectory ◽  
Vertical Profiles ◽  
Ozone Monitoring Instrument ◽  
Uv Index

The temporal and spatial distributions of tropospheric ozone and its precursors (NO2, CO, HCHO) are analyzed over Guangxi (GX) in South China. We used tropospheric column ozone (TCO) from the Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) onboard the Aura satellite (OMI/MLS), NO2 and HCHO from OMI and CO from the Measurements of Pollution in the Troposphere (MOPITT) instrument in the period 2005–2016. The TCO shows strong seasonality, with the highest value in spring and the lowest value observed in the monsoon season. The seasonal variation of HCHO is similar to that of TCO, while NO2 and CO show slightly different patterns with higher values in spring and winter compared to lower values in autumn and summer. The surface ozone, NO2 and CO observed by national air quality monitoring network sites are also compared with satellite-observed TCO, NO2 and CO, showing good agreement for NO2 and CO but a different seasonal pattern for ozone. Unlike TCO, surface ozone has the highest value in autumn and the lowest value in winter. To reveal the difference, the vertical profiles of ozone and CO from the measurement of ozone and water vapor by airbus in-service aircraft (MOZAIC) observations over South China are also examined. The seasonal averaged vertical profiles of ozone and CO show obvious enhancements at 2–6 km altitudes in spring. Furthermore, we investigate the dependence of TCO and surface ozone on meteorology and transport in detail along with the ECMWF reanalysis data, Tropical Rainfall Measuring Mission (TRMM) 3BV42 dataset, OMI ultraviolet index (UV index) dataset, MODIS Fire Radiative Power (FRP) and back trajectory. Our results show that the wind pattern at 800 hPa plays a significant role in determining the seasonality of TCO over GX, especially for the highest value in spring. Trajectory analysis, combined with MODIS FRP suggests that the air masses that passed through the biomass burning (BB) region of Southeast Asia (SEA) induced the enhancement of TCO and CO in the upper-middle troposphere in spring. However, the seasonal cycle of surface ozone is associated with wind patterns at 950 hPa, and the contribution of the photochemical effect is offset by the strong summer monsoon, which results in the maximum surface ozone concentration in post-monsoon September. The variations in the meteorological conditions at different levels and the influence of transport from SEA can account for the vertical distribution of ozone and CO. We conclude that the seasonal distribution of TCO results from the combined impact of meteorology and long-term transport.

scholarly journals The influence of weather-driven processes on tropospheric ozone

2021 ◽  
Author(s):  
Tamara Emmerichs ◽  
Bruno Franco ◽  
Catherine Wespes ◽  
Vinod Kumar ◽  
Andrea Pozzer ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Dry Deposition ◽  
Tropospheric Ozone ◽  
Surface Ozone ◽  
Air Pollutant ◽  
Chemical Production ◽  
Ozone Monitoring Instrument ◽  
Near Surface ◽  
The Impact

Abstract. Near-surface ozone is an harmful air pollutant, which is determined to a considerable extent by weather-controlled processes, and may be significantly impacted by water vapour forming complexes with peroxy radicals. The role of water in the reaction of HO2 radical with nitrogen oxides is known from the literature, and in current models the water complex is considered by assuming a linear dependence on water concentrations. In fact, recent experimental evidence has been published, showing the significant role of water on the kinetics of one of the most important reaction for ozone chemistry, namely NO2 + OH. Here, the available kinetic data for the HOx + NOx reactions have been included in the atmospheric chemistry model ECHAM5/MESSy (EMAC) to test its global significance. Among the modified kinetics, the newly added HNO3 channel from HO2 + NO, dominates, significantly reducing NO2. A major removal process of near-surface ozone is dry deposition accounting for 20 % of the total tropospheric ozone loss mostly occurring over vegetation. However, parameterizations for modelling dry deposition represent a major source of uncertainty for tropospheric ozone simulations. This potentially belongs to the reasons why global models, such as EMAC used here, overestimate ozone with respect to observations. In fact, the employed parameterization is hardly sensitive to local meteorological conditions (e.g., humidity) and lacks non-stomatal deposition. In this study, a dry deposition scheme including these features have been used in EMAC, affecting not only the deposition of ozone but of its precursors, resulting in lower chemical production of ozone. Additionally, we improved the emissions of isoprene and nitrous acid (HONO). Namely, for isoprene emissions we have accounted for the impact of drought stress which confers a higher model sensitivity to meteorology leading to reduced annual emissions down to 32 %. For HONO, we have implemented soil emissions, which depend on soil moisture and thus on precipitation. We estimate for the first time a global source strength of 7 Tg(N) a−1. Furthermore, the usage of a parameterization for the production of lightning NOx that depends on cloud top height contributes to a more realistic representation of NO2 columns over remote oceans with respect to the satellite measurements of the Ozone Monitoring Instrument (OMI). The combination of all the model modifications reduces the simulated global ozone burden by ≈ 20 % to 337 Tg, which is in better agreement with recent estimates. By comparing simulation results with measurements from the Infrared Atmospheric Sounding Interferometer (IASI) and the Tropospheric Ozone Assessment Report (TOAR) databases (of 2009) we demonstrate an overall reduction of the ozone bias by a factor of 2.

scholarly journals An evaluation of the ability of the Ozone Monitoring Instrument (OMI) to observe boundary layer ozone pollution across China: application to 2005–2017 ozone trends

2019 ◽  
Vol 19 (9) ◽  
pp. 6551-6560 ◽  
Author(s):  
Lu Shen ◽  
Daniel J. Jacob ◽  
Xiong Liu ◽  
Guanyu Huang ◽  
Ke Li ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Tropospheric Ozone ◽  
Southern China ◽  
Surface Ozone ◽  
Eastern China ◽  
Ozone Pollution ◽  
Ozone Monitoring Instrument ◽  
Monitoring Instrument ◽  
Ozone Monitoring ◽  
Boundary Layer Ozone

Abstract. Nadir-viewing satellite observations of tropospheric ozone in the UV have been shown to have some sensitivity to boundary layer ozone pollution episodes, but so far they have not yet been compared to surface ozone observations collected by large-scale monitoring networks. Here we use 2013–2017 surface ozone data from China's new Ministry of Ecology and Environment (MEE) network of ∼ 1000 sites, together with vertical profiles from ozonesondes and aircraft, to quantify the ability of tropospheric ozone retrievals from the Ozone Monitoring Instrument (OMI) and to detect boundary layer ozone pollution in China. We focus on summer when ozone pollution in China is most severe and when OMI has the strongest sensitivity. After subtracting the Pacific background, we find that the 2013–2017 mean OMI ozone enhancements over eastern China have strong spatial correlation with the corresponding multiyear means in the surface afternoon observations (R=0.73), and that OMI can estimate these multiyear means in summer afternoon surface ozone with a precision of 8 ppb. The OMI data show significantly higher values on observed surface ozone episode days (>82 ppb) than on non-episode days. Day-to-day correlations with surface ozone are much weaker due to OMI noise and are stronger for sites in southern China (<34∘ N; R=0.3–0.6) than in northern China (R=0.1–0.3) because of weaker retrieval sensitivity and larger upper tropospheric variability in the north. Ozonesonde data show that much of the variability of OMI ozone over southern China in summer is driven by the boundary layer. Comparison of 2005–2009 and 2013–2017 OMI data indicates that mean summer afternoon surface ozone in southern China (including urban and rural regions) has increased by 3.5±3.0 ppb over the 8-year period and that the number of episode days per summer has increased by 2.2±0.4 (as diagnosed by an extreme value model), generally consistent with the few long-term surface records. Ozone increases have been particularly large in the Yangtze River Delta and in the Hubei, Guangxi and Hainan provinces.

scholarly journals Evaluation of ozone profile and tropospheric ozone retrievals from GEMS and OMI spectra

2013 ◽  
Vol 6 (2) ◽  
pp. 239-249 ◽  
Author(s):  
J. Bak ◽  
J. H. Kim ◽  
X. Liu ◽  
K. Chance ◽  
J. Kim
Keyword(s):  
Spectral Resolution ◽  
Tropospheric Ozone ◽  
Stratospheric Ozone ◽  
A Priori ◽  
Ozone Monitoring Instrument ◽  
Satellite Platform ◽  
Ozone Profile ◽  
Retrieval Errors ◽  
Standard Deviations ◽  
Column Ozone

Abstract. South Korea is planning to launch the GEMS (Geostationary Environment Monitoring Spectrometer) instrument into the GeoKOMPSAT (Geostationary Korea Multi-Purpose SATellite) platform in 2018 to monitor tropospheric air pollutants on an hourly basis over East Asia. GEMS will measure backscattered UV radiances covering the 300–500 nm wavelength range with a spectral resolution of 0.6 nm. The main objective of this study is to evaluate ozone profiles and stratospheric column ozone amounts retrieved from simulated GEMS measurements. Ozone Monitoring Instrument (OMI) Level 1B radiances, which have the spectral range 270–500 nm at spectral resolution of 0.42–0.63 nm, are used to simulate the GEMS radiances. An optimal estimation-based ozone profile algorithm is used to retrieve ozone profiles from simulated GEMS radiances. Firstly, we compare the retrieval characteristics (including averaging kernels, degrees of freedom for signal, and retrieval error) derived from the 270–330 nm (OMI) and 300–330 nm (GEMS) wavelength ranges. This comparison shows that the effect of not using measurements below 300 nm on retrieval characteristics in the troposphere is insignificant. However, the stratospheric ozone information in terms of DFS decreases greatly from OMI to GEMS, by a factor of ∼2. The number of the independent pieces of information available from GEMS measurements is estimated to 3 on average in the stratosphere, with associated retrieval errors of ~1% in stratospheric column ozone. The difference between OMI and GEMS retrieval characteristics is apparent for retrieving ozone layers above ~20 km, with a reduction in the sensitivity and an increase in the retrieval errors for GEMS. We further investigate whether GEMS can resolve the stratospheric ozone variation observed from high vertical resolution Earth Observing System (EOS) Microwave Limb Sounder (MLS). The differences in stratospheric ozone profiles between GEMS and MLS are comparable to those between OMI and MLS below ~3 hPa (~40 km), except with slightly larger biases and larger standard deviations by up to 5%. At pressure altitudes above ~3 hPa, GEMS retrievals show strong influence of a priori and large differences with MLS, which, however, can be sufficiently improved by using better a priori information. The GEMS-MLS differences show negative biases of less than 4% for stratospheric column ozone, with standard deviations of 1–3%, while OMI retrievals show similar agreements with MLS except for 1% smaller biases at middle and high latitudes. Based on the comparisons, we conclude that GEMS will measure tropospheric ozone and stratospheric ozone columns with accuracy comparable to that of OMI and ozone profiles with slightly worse performance than that of OMI below ~3 hPa.

scholarly journals Variations in O<sub>3</sub>, CO, and CH<sub>4</sub> over the Bay of Bengal during the summer monsoon season: Ship-borne measurements and model simulations

2016 ◽  
Author(s):  
Imran A. Girach ◽  
Narendra Ojha ◽  
Prabha R. Nair ◽  
Andrea Pozzer ◽  
Yogesh K. Tiwari ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Surface Ozone ◽  
Ozone Production ◽  
Spatial And Temporal Variability ◽  
Summer Monsoon Season ◽  
Rainfall Events ◽  
Model Simulations ◽  
Mixing Ratios

Abstract. We present ship-borne measurements of surface ozone, carbon monoxide and methane over the Bay of Bengal (BoB), the first time such measurements have been taken during the summer monsoon season, as a part of the Continental Tropical Convergence Zone (CTCZ) experiment during 2009. O3, CO, and CH4 mixing ratios exhibited significant spatial and temporal variability in the ranges of 8–54 nmol mol−1, 50–200 nmol mol−1, and 1.57–2.15 µmol mol−1, with means of 29.7 ± 6.8 nmol mol−1, 96 ± 25 nmol mol−1, and 1.83 ± 0.14 µmol mol−1, respectively. The average mixing ratios of trace gases over northern BoB (O3: 30 ± 7 nmol mol−1, CO: 95 ± 25 nmol mol−1, CH4: 1.86 ± 0.12 µmol mol−1), in airmasses from northern or central India, did not differ much from those over central BoB (O3: 27 ± 5 nmol mol−1, CO: 101 ± 27 nmol mol−1, CH4: 1.72 ± 0.14 µmol mol−1), in airmasses from southern India. Spatial variability is observed to be most significant for CH4. The ship-based observations, in conjunction with backward air trajectories and ground-based measurements over the Indian region, are analyzed to estimate a net ozone production of 1.5–4 nmol mol−1 day−1 in the outflow. Ozone mixing ratios over the BoB showed large reductions (by ~ 20 nmol mol−1) during four rainfall events. Temporal changes in the meteorological parameters, in conjunction with ozone vertical profiles, indicate that these low ozone events are associated with downdrafts of free-tropospheric ozone-poor airmasses. While the observed variations in O3 and CO are successfully reproduced using the Weather Research and Forecasting model with Chemistry (WRF-Chem), this model overestimates mean concentrations by about 20 %, generally overestimating O3 mixing ratios during the rainfall events. Analysis of the chemical tendencies from model simulations for a low-O3 event on August 10, 2009, captured successfully by the model, shows the key role of horizontal advection in rapidly transporting ozone-rich airmasses across the BoB. Our study fills a gap in the availability of trace gas measurements over the BoB, and when combined with data from previous campaigns, reveals large seasonal amplitude (~ 39 and ~ 207 nmol mol−1 for O3 and CO, respectively) over the northern BoB.

scholarly journals Impact of uncertainties in inorganic chemical rate constants on tropospheric composition and ozone radiative forcing

2017 ◽  
Author(s):  
Ben Newsome ◽  
Mat Evans
Keyword(s):  
Rate Constant ◽  
Atmospheric Chemistry ◽  
Rate Constants ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Transport Model ◽  
Surface Ozone ◽  
Photolysis Rates ◽  
The Impact ◽  
Chemical Rate

Abstract. Chemical rate constants determine the composition of the atmosphere and how this composition has changed over time. They are central to our understanding of climate change and air quality degradation. Atmospheric chemistry models, whether online or offline, box, regional or global use these rate constants. Expert panels synthesise laboratory measurements, making recommendations for the rate constants that should be used. This results in very similar or identical rate constants being used by all models. The inherent uncertainties in these recommendations are, in general, therefore ignored. We explore the impact of these uncertainties on the composition of the troposphere using the GEOS-Chem chemistry transport model. Based on the JPL and IUPAC evaluations we assess 50 mainly inorganic rate constants and 10 photolysis rates, through simulations where we increase the rate of the reactions to the 1σ upper value recommended by the expert panels. We assess the impact on 4 standard metrics: annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime. Uncertainty in the rate constants for NO2 + OH    M →  HNO3, OH + CH4 → CH3O2 + H2O and O3 + NO → NO2 + O2 are the three largest source of uncertainty in these metrics. We investigate two methods of assessing these uncertainties, addition in quadrature and a Monte Carlo approach, and conclude they give similar outcomes. Combining the uncertainties across the 60 reactions, gives overall uncertainties on the annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime of 11, 12, 17 and 17 % respectively. These are larger than the spread between models in recent model inter-comparisons. Remote regions such as the tropics, poles, and upper troposphere are most uncertain. This chemical uncertainty is sufficiently large to suggest that rate constant uncertainty should be considered when model results disagree with measurement. Calculations for the pre-industrial allow a tropospheric ozone radiative forcing to be calculated of 0.412 ± 0.062 Wm−2. This uncertainty (15 %) is comparable to the inter-model spread in ozone radiative forcing found in previous model-model inter-comparison studies where the rate constants used in the models are all identical or very similar. Thus the uncertainty of tropospheric ozone radiative forcing should expanded to include this additional source of uncertainty. These rate constant uncertainties are significant and suggest that refinement of supposedly well known chemical rate constants should be considered alongside other improvements to enhance our understanding of atmospheric processes.

scholarly journals Increasing surface ozone concentrations in the background atmosphere of Southern China, 1994–2007

2009 ◽  
Vol 9 (16) ◽  
pp. 6217-6227 ◽  
Author(s):  
T. Wang ◽  
X. L. Wei ◽  
A. J. Ding ◽  
C. N. Poon ◽  
K. S. Lam ◽  
...  
Keyword(s):  
Hong Kong ◽  
South China ◽  
Surface Ozone ◽  
Eastern China ◽  
Rate Of Change ◽  
Urban Site ◽  
Coastal Regions ◽  
Air Masses ◽  
Background Ozone ◽  
Rate Of Increase

Abstract. Tropospheric ozone is of great importance with regard to air quality, atmospheric chemistry, and climate change. In this paper we report the first continuous record of surface ozone in the background atmosphere of South China. The data were obtained from 1994 to 2007 at a coastal site in Hong Kong, which is strongly influenced by the outflow of Asian continental air during the winter and the inflow of maritime air from the subtropics in the summer. Three methods are used to derive the rate of change in ozone. A linear fit to the 14-year record shows that the ozone concentration increased by 0.58 ppbv/yr, whereas comparing means in years 1994–2000 and 2001–2007 gives an increase of 0.87 ppbv/yr for a 7-year period. The ozone changes in air masses from various source regions are also examined. Using local wind and carbon monoxide (CO) data to filter out local influence, we find that ozone increased by 0.94 ppbv/yr from 1994–2000 to 2001–2007 in air masses from Eastern China, with similar changes in the other two continent-influenced air-mass groups, but no statistically significant change in the marine air. An examination of the nitrogen dioxide (NO2) column obtained from GOME and SCIAMACHY reveals an increase in atmospheric NO2 in China's three fastest developing coastal regions, whereas NO2 in other parts of Asia decreased during the same period, and no obvious trend over the main shipping routes in the South China Sea was indicated. Thus the observed increase in background ozone in Hong Kong is most likely due to the increased emissions of NO2 (and possibly volatile organic compounds (VOCs) as well) in the upwind coastal regions of mainland China. The CO data at Hok Tsui showed less definitive changes compared to the satellite NO2 column. The increase in background ozone likely made a strong contribution (81%) to the rate of increase in "total ozone" at an urban site in Hong Kong, suggesting the need to consider distant sources when developing long-term strategies to mitigate local ozone pollution.

scholarly journals Tropospheric ozone over Equatorial Africa: regional aspects from the MOZAIC data

2004 ◽  
Vol 4 (3) ◽  
pp. 3285-3332 ◽  
Author(s):  
B. Sauvage ◽  
V. Thouret ◽  
J.-P. Cammas ◽  
F. Gheusi ◽  
G. Athier ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Tropospheric Ozone ◽  
Central Africa ◽  
Lower Troposphere ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Vertical Profiles ◽  
Middle Troposphere ◽  
Ozone Distribution ◽  
Equatorial Africa

Abstract. We analyze MOZAIC ozone observations recorded over Equatorial Africa, from April 1997 to March 2003 to give the first ozone climatology of this region. The monthly mean vertical profiles have been systematically analyzed with monthly mean ECMWF data using a Lagrangian-model (LAGRANTO). We assess the roles played by the dynamical features of Equatorial Africa and the intense biomass burning sources within the region in defining the ozone distribution. The lower troposphere exhibits layers of enhanced ozone during the biomass burning season in each hemisphere (boreal winter in the northern tropics and boreal summer in the southern tropics). The monthly mean vertical profiles of ozone are clearly influenced by the local dynamical situation. Over the Gulf of Guinea during boreal winter, the ozone profile is characterized by systematically high ozone below 650 hPa. This is due to the high stability caused by the Harmattan winds in the lower troposphere and the blocking Saharan anticyclone in the middle troposphere that prevents any efficient vertical mixing. In contrast, Central African enhancements are not only found in the lower troposphere but throughout the troposphere. The boreal summer ozone maximum in the lower troposphere of Central Africa continues up to November in the middle troposphere due to the influx of air masses laden with biomass burning products from Brazil and Southern Africa. Despite its southern latitude, Central Africa during the boreal winter is also under the influence of the northern tropical fires. This phenomenon is known as the "ozone paradox". However, the tropospheric ozone columns calculated from the MOZAIC data give evidence that the Tropical Tropospheric Ozone Column (TTOC) maximum over Africa swings from West Africa in DJF to Central Africa in JJA. This contrasts with studies based on TOMS satellite data. A rough assessment of the regional ozone budget shows that the northern tropics fires in boreal winter might contribute up to 20% of the global photochemical ozone production. This study gives the first detailed picture of the ozone distribution over Equatorial Africa that should be used to validate both global models over this region and future satellite products.

scholarly journals Tropospheric Ozone Assessment Report: Tropospheric ozone from 1877 to 2016, observed levels, trends and uncertainties

Elem Sci Anth ◽  
2019 ◽  
Vol 7 ◽  
Author(s):  
David Tarasick ◽  
Ian E. Galbally ◽  
Owen R. Cooper ◽  
Martin G. Schultz ◽  
Gerard Ancellet ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Mixed Boundary ◽  
Surface Ozone ◽  
Great Majority ◽  
Measurement Methods ◽  
Uv Absorption ◽  
Lower Atmosphere ◽  
Polar Regions ◽  
Free Troposphere ◽  
Ozone Measurement

From the earliest observations of ozone in the lower atmosphere in the 19th century, both measurement methods and the portion of the globe observed have evolved and changed. These methods have different uncertainties and biases, and the data records differ with respect to coverage (space and time), information content, and representativeness. In this study, various ozone measurement methods and ozone datasets are reviewed and selected for inclusion in the historical record of background ozone levels, based on relationship of the measurement technique to the modern UV absorption standard, absence of interfering pollutants, representativeness of the well-mixed boundary layer and expert judgement of their credibility. There are significant uncertainties with the 19th and early 20th-century measurements related to interference of other gases. Spectroscopic methods applied before 1960 have likely underestimated ozone by as much as 11% at the surface and by about 24% in the free troposphere, due to the use of differing ozone absorption coefficients. There is no unambiguous evidence in the measurement record back to 1896 that typical mid-latitude background surface ozone values were below about 20 nmol mol–1, but there is robust evidence for increases in the temperate and polar regions of the northern hemisphere of 30–70%, with large uncertainty, between the period of historic observations, 1896–1975, and the modern period (1990–2014). Independent historical observations from balloons and aircraft indicate similar changes in the free troposphere. Changes in the southern hemisphere are much less. Regional representativeness of the available observations remains a potential source of large errors, which are difficult to quantify. The great majority of validation and intercomparison studies of free tropospheric ozone measurement methods use ECC ozonesondes as reference. Compared to UV-absorption measurements they show a modest (~1–5% ±5%) high bias in the troposphere, but no evidence of a change with time. Umkehr, lidar, and FTIR methods all show modest low biases relative to ECCs, and so, using ECC sondes as a transfer standard, all appear to agree to within one standard deviation with the modern UV-absorption standard. Other sonde types show an increase of 5–20% in sensitivity to tropospheric ozone from 1970–1995. Biases and standard deviations of satellite retrieval comparisons are often 2–3 times larger than those of other free tropospheric measurements. The lack of information on temporal changes of bias for satellite measurements of tropospheric ozone is an area of concern for long-term trend studies.

scholarly journals Ozone and NO<sub>x</sub> chemistry in the eastern US: evaluation of CMAQ/CB05 with satellite (OMI) data

2015 ◽  
Vol 15 (4) ◽  
pp. 4427-4461 ◽  
Author(s):  
T. P. Canty ◽  
L. Hembeck ◽  
T. P. Vinciguerra ◽  
D. C. Anderson ◽  
D. L. Goldberg ◽  
...  
Keyword(s):  
Air Quality ◽  
Surface Ozone ◽  
Quality Standards ◽  
Ambient Air ◽  
Daily Maximum ◽  
Air Quality Model ◽  
Ozone Monitoring Instrument ◽  
Air Quality Standards ◽  
The Us ◽  
Us Northeast

Abstract. Regulatory air quality models, such as the Community Multiscale Air Quality model (CMAQ), are used by federal and state agencies to guide policy decisions that determine how to best achieve adherence with National Ambient Air Quality Standards for surface ozone. We use observations of ozone and its important precursor NO2 to test the representation of the photochemistry and emission of ozone precursors within CMAQ. Observations of tropospheric column NO2 from the Ozone Monitoring Instrument (OMI), retrieved by two independent groups, show that the model overestimates urban NO2 and underestimates rural NO2 under all conditions examined for July and August 2011 in the US Northeast. The overestimate of the urban to rural ratio of tropospheric column NO2 for this baseline run of CMAQ (CB05 mechanism, mobile NOx emissions from the National Emissions Inventory; isoprene emissions from MEGAN v2.04) suggests this model may under estimate the importance of interstate transport of NOx. This CMAQ simulation leads to a considerable overestimate of the 2 month average of 8 h daily maximum surface ozone in the US Northeast, as well as an overestimate of 8 h ozone at AQS sites during days when the state of Maryland experienced NAAQS exceedances. We have implemented three changes within CMAQ motivated by OMI NO2 as well as aircraft observations obtained in July 2011 during the NASA DISCOVER-AQ campaign: (a) the modeled lifetime of organic nitrates within CB05 has been reduced by a factor of 10, (b) emissions of NOx from mobile sources has been reduced by a factor of 2, and (c) isoprene emissions have been reduced by using MEGAN v2.10 rather than v2.04. Compared to the baseline simulation, the CMAQ run using all three of these changes leads to a considerably better simulation of the ratio of urban to rural column NO2, better agreement with the 2 month average of daily 8 h maximum ozone in the US Northeast, fewer number of false positives of an ozone exceedance throughout the domain, as well as an unbiased simulation of surface ozone at ground based AQS sites in Maryland that experienced an ozone exceedance during July and August 2007. These modifications to CMAQ may provide a framework for use in studies focused on achieving future adherence to specific air quality standards for surface ozone by reducing emission of NOx from various anthropogenic sectors.

scholarly journals The role of open lead interactions in atmospheric ozone variability between Arctic coastal and inland sites

Elem Sci Anth ◽  
2016 ◽  
Vol 4 ◽  
Author(s):  
Peter K. Peterson ◽  
Kerri A. Pratt ◽  
William R. Simpson ◽  
Son V. Nghiem ◽  
Lemuel X. Pérez Pérez ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
Ozone Depletion ◽  
Surface Ozone ◽  
Optical Absorption Spectroscopy ◽  
Atmospheric Ozone ◽  
Vertical Profiles ◽  
Large Spatial Scale ◽  
Near Surface ◽  
Air Masses

Abstract Boundary layer atmospheric ozone depletion events (ODEs) are commonly observed across polar sea ice regions following polar sunrise. During March-April 2005 in Alaska, the coastal site of Barrow and inland site of Atqasuk experienced ODEs (O3&lt; 10 nmol mol-1) concurrently for 31% of the observations, consistent with large spatial scale ozone depletion. However, 7% of the time ODEs were exclusively observed inland at Atqasuk. This phenomenon also occurred during one of nine flights during the BRomine, Ozone, and Mercury EXperiment (BROMEX), when atmospheric vertical profiles at both sites showed near-surface ozone depletion only at Atqasuk on 28 March 2012. Concurrent in-flight BrO measurements made using nadir scanning differential optical absorption spectroscopy (DOAS) showed the differences in ozone vertical profiles at these two sites could not be attributed to differences in locally occurring halogen chemistry. During both studies, backward air mass trajectories showed that the Barrow air masses observed had interacted with open sea ice leads, causing increased vertical mixing and recovery of ozone at Barrow and not Atqasuk, where the air masses only interacted with tundra and consolidated sea ice. These observations suggest that, while it is typical for coastal and inland sites to have similar ozone conditions, open leads may cause heterogeneity in the chemical composition of the springtime Arctic boundary layer over coastal and inland areas adjacent to sea ice regions.

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