scholarly journals Regional and intercontinental pollution signatures on modeled and measured PAN at northern mid-latitude mountain sites

2018 ◽  
Author(s):  
Arlene M. Fiore ◽  
Emily V. Fischer ◽  
Shubha Pandey Deolal ◽  
Oliver Wild ◽  
Dan Jaffe ◽  
...  
Keyword(s):  
Transport Model ◽  
Ozone Production ◽  
Anthropogenic Emissions ◽  
Chemical Transport Model ◽  
Reservoir Species ◽  
Remote Troposphere ◽  
Global Chemical Transport Model ◽  
Peroxy Acetyl Nitrate ◽  
Source Receptor Relationships

Abstract. Peroxy acetyl nitrate (PAN) is the most important reservoir species for nitrogen oxides (NOx) in the remote troposphere. Upon decomposition in remote regions, PAN promotes efficient ozone production. We evaluate monthly mean PAN abundances from global chemical transport model simulations (HTAP1) for 2001 with measurements from five northern mid-latitude mountain sites (four European and one North American). The multi-model mean generally captures the observed monthly mean PAN but individual models simulate a factor of ~ 4–8 range in monthly abundances. We quantify PAN source-receptor relationships at the measurement sites with sensitivity simulations that decrease regional anthropogenic emissions of PAN (and ozone) precursors by 20 % from North America (NA), Europe (EU), and East Asia (EA). The HTAP1 models attribute more of the observed PAN at Jungfraujoch (Switzerland) to emissions in NA and EA, and less to EU, than a prior trajectory-based estimate. The trajectory-based and modeling approaches agree that EU emissions play a role in the observed springtime PAN maximum at Jungfraujoch. The signal from anthropogenic emissions on PAN is strongest at Jungfraujoch and Mount Bachelor (Oregon, U.S.A.) during April. In this month, PAN source-receptor relationships correlate both with model differences in regional anthropogenic volatile organic compound (AVOC) emissions and with ozone source-receptor relationships. PAN observations at mountaintop sites can thus provide key information for evaluating models, including links between PAN and ozone production and source-receptor relationships. Establishing routine, long-term, mountaintop measurements is essential given the large observed interannual variability in PAN.

scholarly journals Unraveling pathways of elevated ozone induced by the 2020 lockdown in Europe by an observationally constrained regional model using TROPOMI

2021 ◽  
Vol 21 (24) ◽  
pp. 18227-18245
Author(s):  
Amir H. Souri ◽  
Kelly Chance ◽  
Juseon Bak ◽  
Caroline R. Nowlan ◽  
Gonzalo González Abad ◽  
...  
Keyword(s):  
Transport Model ◽  
Atmospheric Transport ◽  
Model Simulation ◽  
Surface Ozone ◽  
Ozone Production ◽  
Anthropogenic Emissions ◽  
Nox Emissions ◽  
Chemical Transport Model ◽  
Voc Emissions ◽  
Constrained Model

Abstract. Questions about how emissions are changing during the COVID-19 lockdown periods cannot be answered by observations of atmospheric trace gas concentrations alone, in part due to simultaneous changes in atmospheric transport, emissions, dynamics, photochemistry, and chemical feedback. A chemical transport model simulation benefiting from a multi-species inversion framework using well-characterized observations should differentiate those influences enabling to closely examine changes in emissions. Accordingly, we jointly constrain NOx and VOC emissions using well-characterized TROPOspheric Monitoring Instrument (TROPOMI) HCHO and NO2 columns during the months of March, April, and May 2020 (lockdown) and 2019 (baseline). We observe a noticeable decline in the magnitude of NOx emissions in March 2020 (14 %–31 %) in several major cities including Paris, London, Madrid, and Milan, expanding further to Rome, Brussels, Frankfurt, Warsaw, Belgrade, Kyiv, and Moscow (34 %–51 %) in April. However, NOx emissions remain at somewhat similar values or even higher in some portions of the UK, Poland, and Moscow in March 2020 compared to the baseline, possibly due to the timeline of restrictions. Comparisons against surface monitoring stations indicate that the constrained model underrepresents the reduction in surface NO2. This underrepresentation correlates with the TROPOMI frequency impacted by cloudiness. During the month of April, when ample TROPOMI samples are present, the surface NO2 reductions occurring in polluted areas are described fairly well by the model (model: −21 ± 17 %, observation: −29 ± 21 %). The observational constraint on VOC emissions is found to be generally weak except for lower latitudes. Results support an increase in surface ozone during the lockdown. In April, the constrained model features a reasonable agreement with maximum daily 8 h average (MDA8) ozone changes observed at the surface (r=0.43), specifically over central Europe where ozone enhancements prevail (model: +3.73 ± 3.94 %, +1.79 ppbv, observation: +7.35 ± 11.27 %, +3.76 ppbv). The model suggests that physical processes (dry deposition, advection, and diffusion) decrease MDA8 surface ozone in the same month on average by −4.83 ppbv, while ozone production rates dampened by largely negative JNO2[NO2]-kNO+O3[NO][O3] become less negative, leading ozone to increase by +5.89 ppbv. Experiments involving fixed anthropogenic emissions suggest that meteorology contributes to 42 % enhancement in MDA8 surface ozone over the same region with the remaining part (58 %) coming from changes in anthropogenic emissions. Results illustrate the capability of satellite data of major ozone precursors to help atmospheric models capture ozone changes induced by abrupt emission anomalies.

scholarly journals Effect of changing NO<sub><i>x</i></sub> lifetime on the seasonality and long-term trends of satellite-observed tropospheric NO<sub>2</sub> columns over China

2019 ◽  
Author(s):  
Viral Shah ◽  
Daniel J. Jacob ◽  
Ke Li ◽  
Rachel F. Silvern ◽  
Shixian Zhai ◽  
...  
Keyword(s):  
Transport Model ◽  
Eastern China ◽  
Anthropogenic Emissions ◽  
Organic Nitrates ◽  
Nox Emissions ◽  
Chemical Transport Model ◽  
Volatile Organic ◽  
Tropospheric No2 ◽  
Long Term Trends

Abstract. Satellite observations of tropospheric NO2 columns are extensively used to infer trends in anthropogenic emissions of nitrogen oxides (NOx ≡ NO + NO2), but this may be complicated by trends in NOx lifetime. Here we use 2004–2018 observations from the OMI satellite-based instrument (QA4ECV and POMINO v2 retrievals) to examine the seasonality and trends of tropospheric NO2 columns over central-eastern China, and we interpret the results with the GEOS-Chem chemical transport model. The observations show a factor of 3 increase in NO2 columns from summer to winter, which we explain in GEOS-Chem as reflecting a longer NOx lifetime in winter than in summer (21 h versus 5.9 h in 2017). The 2005–2018 summer trends of OMI NO2 closely follow the trends in the Multi-resolution Emission Inventory for China (MEIC), with a rise over the 2005–2011 period and a 25 % decrease since. We find in GEOS-Chem no significant trend of the NOx lifetime in summer, supporting the emission trend reported by MEIC. The winter trend of OMI NO2 is steeper than in summer over the entire period, which we attribute to a decrease in NOx lifetime at lower NOx emissions. Half of the NOx sink in winter is from N2O5 hydrolysis, which counterintuitively becomes more efficient as NOx emissions decrease due to less titration of ozone at night. Formation of organic nitrates also becomes an increasing sink of NOx as NOx emissions decrease but emissions of volatile organic compounds (VOCs) do not.

scholarly journals A new diagnostic for tropospheric ozone production

2017 ◽  
Author(s):  
Peter M. Edwards ◽  
Mathew J. Evans
Keyword(s):  
Air Quality ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Chemical Transport ◽  
Ozone Production ◽  
Chemical Transport Model ◽  
Organic Species ◽  
Earth’S Climate ◽  
Oxidation Of Organics

Abstract. Tropospheric ozone is important for the Earth’s climate and air quality. It is produced during the oxidation of organics in the presence of nitrogen oxides. Due to the range of organic species emitted and the chain like nature of their oxidation, this chemistry is complex and understanding the role of different processes (emission, deposition, chemistry) is difficult. We demonstrate a new methodology for diagnosing ozone production based on the processing of bonds contained within emitted molecules, the fate of which is determined by the conservation of spin of the bonding electrons. Using this methodology to diagnose ozone production in the GEOS-Chem chemical transport model, we demonstrate its advantages over the standard diagnostic. We show that the number of bonds emitted, their chemistry and lifetime, and feedbacks on OH are all important in determining the ozone production within the model and its sensitivity to changes. This insight may allow future model-model comparisons to better identify the root causes of model differences.

scholarly journals Analysis of a Regional Scale Chemical-Transport Model to Investigate the Potential Capability of Satellites for Identifying a Widespread Air Pollution Event

2017 ◽  
Author(s):  
Jason Welsh ◽  
Jack Fishman
Keyword(s):  
Transport Model ◽  
Regional Scale ◽  
Ozone Production ◽  
Metropolitan Region ◽  
Trace Gas ◽  
Chemical Transport Model ◽  
Satellite Measurements ◽  
Pollution Event ◽  
Surface O3 ◽  
Good Agreement

We use a regional scale photochemical transport model to investigate the surface concentrations and column integrated amounts of ozone (O3) and nitrogen dioxide (NO2) during a pollution event that occurred in the St. Louis metropolitan region in 2012. These trace gases will be two of the primary constituents that will be measured by TEMPO, an instrument on a geostationary platform, which will result in a dataset that has hourly temporal resolution during the daytime and ~4 km spatial resolution. Although air quality managers are most concerned with surface concentrations, satellite measurements provide a quantity that reflects a column amount, which may or may not be directly relatable to what is measured at the surface. The model results provide good agreement with observed surface O3 concentrations, which is the only trace gas dataset that can be used for verification. The model shows that a plume of O3 extends downwind from St. Louis and contains an integrated amount of ozone of ~ 16 DU (1 DU = 2.69 x 1016 mol. cm-2), a quantity that is two to three times lower than what was observed by satellite measurements during two massive pollution episodes in the 1980s. Based on the smaller isolatable emissions coming from St. Louis, this quantity is not unreasonable, but may also reflect the reduction of photochemical ozone production due to the implementation of emission controls that have gone into effect in the past few decades.

scholarly journals Atmospheric peroxyacetyl nitrate (PAN): a global budget and source attribution

2014 ◽  
Vol 14 (5) ◽  
pp. 2679-2698 ◽  
Author(s):  
E. V. Fischer ◽  
D. J. Jacob ◽  
R. M. Yantosca ◽  
M. P. Sulprizio ◽  
D. B. Millet ◽  
...  
Keyword(s):  
Transport Model ◽  
Oxidation Products ◽  
Anthropogenic Sources ◽  
Source Attribution ◽  
Chemical Transport Model ◽  
Peroxyacetyl Nitrate ◽  
Northern Latitudes ◽  
Remote Troposphere ◽  
Terpene Oxidation ◽  
Lightning Nox

Abstract. Peroxyacetyl nitrate (PAN) formed in the atmospheric oxidation of non-methane volatile organic compounds (NMVOCs) is the principal tropospheric reservoir for nitrogen oxide radicals (NOx = NO + NO2). PAN enables the transport and release of NOx to the remote troposphere with major implications for the global distributions of ozone and OH, the main tropospheric oxidants. Simulation of PAN is a challenge for global models because of the dependence of PAN on vertical transport as well as complex and uncertain NMVOC sources and chemistry. Here we use an improved representation of NMVOCs in a global 3-D chemical transport model (GEOS-Chem) and show that it can simulate PAN observations from aircraft campaigns worldwide. The immediate carbonyl precursors for PAN formation include acetaldehyde (44% of the global source), methylglyoxal (30%), acetone (7%), and a suite of other isoprene and terpene oxidation products (19%). A diversity of NMVOC emissions is responsible for PAN formation globally including isoprene (37%) and alkanes (14%). Anthropogenic sources are dominant in the extratropical Northern Hemisphere outside the growing season. Open fires appear to play little role except at high northern latitudes in spring, although results are very sensitive to plume chemistry and plume rise. Lightning NOx is the dominant contributor to the observed PAN maximum in the free troposphere over the South Atlantic.

Investigation of long-term fate of mercury in the ocean using a new global model

2020 ◽  
Author(s):  
Toru Kawai ◽  
Takeo Sakurai ◽  
Noriyuki Suzuki
Keyword(s):  
Industrial Revolution ◽  
Transport Model ◽  
Marine Ecosystem ◽  
Turnover Time ◽  
Global Model ◽  
Previous Model ◽  
Phase Lag ◽  
Anthropogenic Emission ◽  
Chemical Transport Model

&lt;p&gt;Numerical modeling is useful for evaluating the international efforts, such as the Minamata Convention on Mercury, that are directed towards the reduction of anthropogenic emissions. We have developed a new global model for mercury, denoted FATE-Hg, which is based on a fully coupled atmosphere-ocean chemical transport model and low and high-order marine ecosystem models. The model considers methylated mercury production in the open ocean seawater, bioconcentration, and food-web biomagnification from particle organic matter to fish. In this study, we performed a long-term simulation over three centuries with changes in anthropogenic emission since the Industrial Revolution, and investigated the long-term evolution of total mercury (THg) in the ocean. The simulated oceanic THg showed a phase lag of 5&amp;#8211;10 years from the anthropogenic emission in the surface-intermediate oceans. As of 2010, oceanic THg was 410 Gg, which is 1.6&amp;#8211;16.9 times higher than that estimated by the previous model. The estimated overall turnover time of oceanic THg determined by our model was 320 years, which is significantly shorter than those estimated by previous model-based studies. Additionally, we estimated geographic THg sources in the upper ocean. The results showed that North America (NA), Europe (EU), and East Asia are the dominant source regions in most ocean sections in the Northern Hemisphere, though the emissions from NA and EU have fall considerably since the 1970s. This result indicated that a significant amount of mercury that had been emitted from NA and EU in the past persists in present-day seawater.&lt;/p&gt;

Validation of nitrogen dry deposition modelling above a mixed forest using high-frequency flux measurements

2020 ◽  
Author(s):  
Pascal Wintjen ◽  
Frederik Schrader ◽  
Martijn Schaap ◽  
Burkhard Beudert ◽  
Christian Brümmer
Keyword(s):  
Dry Deposition ◽  
High Frequency ◽  
Transport Model ◽  
Mixed Forest ◽  
Reactive Nitrogen ◽  
Nitrogen Compounds ◽  
Chemical Transport Model ◽  
Flux Measurements ◽  
Deposition Models

&lt;p&gt;Reactive nitrogen (N&lt;sub&gt;r&lt;/sub&gt;) compounds comprise essential nutrients for plants. However, a large supply of nitrogen by fertilization through atmospheric deposition may be harmful for ecosystems such as peatlands and may lead to a loss of biodiversity, soil acidification and eutrophication. In addition, nitrogen compounds may cause adverse human health impacts. Large parts of N&lt;sub&gt;r&lt;/sub&gt; emissions originate from anthropogenic activities. &amp;#160;Emission hotspots of &amp;#931;N&lt;sub&gt;r&lt;/sub&gt;, i.e. the sum of all N&lt;sub&gt;r&lt;/sub&gt; compounds, are related to crop production and livestock farming (mainly through ammonia, NH&lt;sub&gt;3&lt;/sub&gt;) and fossil fuel combustion by transport and industry (mainly through nitrogen oxides, NO&lt;sub&gt;2 &lt;/sub&gt;and NO). Such additional amount of N&lt;sub&gt;r&lt;/sub&gt; will enhance its biosphere-atmosphere exchange, affect plant health and can influence its photosynthetic capacity. Therefore, it is necessary to thoroughly estimate the nitrogen exchange between biosphere and atmosphere.&lt;/p&gt;&lt;p&gt;For measuring the nitrogen mixing ratios a converter for reactive nitrogen (TRANC: Total Reactive Atmospheric Nitrogen Converter) was used. The TRANC converts all reactive nitrogen compounds, except for nitrous oxide (N&lt;sub&gt;2&lt;/sub&gt;O), to nitric oxide (NO) and is coupled to a fast-response chemiluminescence detector (CLD). Due to a low detection limit and a response time of about 0.3s the TRANC-CLD system can be used for flux calculation based on the eddy covariance (EC) technique. Flux losses, which are related to the experimental setup, different response characteristics and the general high reactivity of most N gases and aerosols, occur in the high frequency range. We estimated damping factors of approximately 20% with an empirical cospectral approach.&lt;/p&gt;&lt;p&gt;For getting a reliable prediction of &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; fluxes through deposition models, long-term flux measurements offer the possibility to verify the nitrogen uptake capacity and to investigate exchange characteristics of &amp;#931;N&lt;sub&gt;r &lt;/sub&gt;in different ecosystems.&lt;/p&gt;&lt;p&gt;In this study, we compare modelled dry deposition fluxes using the deposition module DEPAC (DEPosition of Acidifying Compounds) within the chemical transport model LOTOS-EUROS (LOng Term Ozone Simulation &amp;#8211; EURopean Operational Smog) against &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; flux measurements of the TRANC-CLD for a remote mixed forest site with hardly any local anthropogenic emission sources. This procedure allows to determine the background load and the natural exchange characteristics of nitrogen under low atmospheric concentrations. Therefore, the broad-scale dry deposition predicted directly by LOTOS-EUROS was compared to site-specific modelling results obtained using measured meteorological input data as well as the directly measured &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; fluxes. In addition, the influence of land-use weighting in LOTOS-EUROS was examined. We further compare our results to &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; deposition estimates obtained with canopy budget techniques. Measured &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; dry deposition at the site was 4.5 kg N ha&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;, in close agreement with modelled estimates using DEPAC with measured drivers (5.2 kg N ha&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;) and as integrated in the chemical transport model LOTOS-EUROS (5.2 kg N ha&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; to 6.9 kg N ha&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; depending on the weighting of land-use classes).&lt;/p&gt;&lt;p&gt;Our study is the first one presenting 2.5 years flux measurements of &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; above a remote mixed forest. Further verifications of long-term flux measurements against deposition models are useful to improve them and result in better understanding of exchange processes of &amp;#931;N&lt;sub&gt;r&lt;/sub&gt;.&lt;/p&gt;

scholarly journals Source attribution of Arctic black carbon constrained by aircraft and surface measurements

2017 ◽  
Vol 17 (19) ◽  
pp. 11971-11989 ◽  
Author(s):  
Jun-Wei Xu ◽  
Randall V. Martin ◽  
Andrew Morrow ◽  
Sangeeta Sharma ◽  
Lin Huang ◽  
...  
Keyword(s):  
North America ◽  
Biomass Burning ◽  
Western Siberia ◽  
Transport Model ◽  
Chemical Transport ◽  
The Arctic ◽  
Anthropogenic Emissions ◽  
Chemical Transport Model ◽  
Northern Asia ◽  
Airborne Measurements

Abstract. Black carbon (BC) contributes to Arctic warming, yet sources of Arctic BC and their geographic contributions remain uncertain. We interpret a series of recent airborne (NETCARE 2015; PAMARCMiP 2009 and 2011 campaigns) and ground-based measurements (at Alert, Barrow and Ny-Ålesund) from multiple methods (thermal, laser incandescence and light absorption) with the GEOS-Chem global chemical transport model and its adjoint to attribute the sources of Arctic BC. This is the first comparison with a chemical transport model of refractory BC (rBC) measurements at Alert. The springtime airborne measurements performed by the NETCARE campaign in 2015 and the PAMARCMiP campaigns in 2009 and 2011 offer BC vertical profiles extending to above 6 km across the Arctic and include profiles above Arctic ground monitoring stations. Our simulations with the addition of seasonally varying domestic heating and of gas flaring emissions are consistent with ground-based measurements of BC concentrations at Alert and Barrow in winter and spring (rRMSE  < 13 %) and with airborne measurements of the BC vertical profile across the Arctic (rRMSE  = 17 %) except for an underestimation in the middle troposphere (500–700 hPa).Sensitivity simulations suggest that anthropogenic emissions in eastern and southern Asia have the largest effect on the Arctic BC column burden both in spring (56 %) and annually (37 %), with the largest contribution in the middle troposphere (400–700 hPa). Anthropogenic emissions from northern Asia contribute considerable BC (27 % in spring and 43 % annually) to the lower troposphere (below 900 hPa). Biomass burning contributes 20 % to the Arctic BC column annually.At the Arctic surface, anthropogenic emissions from northern Asia (40–45 %) and eastern and southern Asia (20–40 %) are the largest BC contributors in winter and spring, followed by Europe (16–36 %). Biomass burning from North America is the most important contributor to all stations in summer, especially at Barrow.Our adjoint simulations indicate pronounced spatial heterogeneity in the contribution of emissions to the Arctic BC column concentrations, with noteworthy contributions from emissions in eastern China (15 %) and western Siberia (6.5 %). Although uncertain, gas flaring emissions from oilfields in western Siberia could have a striking impact (13 %) on Arctic BC loadings in January, comparable to the total influence of continental Europe and North America (6.5 % each in January). Emissions from as far as the Indo-Gangetic Plain could have a substantial influence (6.3 % annually) on Arctic BC as well.

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