scholarly journals Using satellite observations of tropospheric NO<sub>2</sub> columns to infer long-term trends in US NO<sub><i>x</i></sub> emissions: the importance of accounting for the free tropospheric NO<sub>2</sub> background

2019 ◽  
Vol 19 (13) ◽  
pp. 8863-8878 ◽  
Author(s):  
Rachel F. Silvern ◽  
Daniel J. Jacob ◽  
Loretta J. Mickley ◽  
Melissa P. Sulprizio ◽  
Katherine R. Travis ◽  
...  
Keyword(s):  
Environmental Protection Agency ◽  
Model Simulation ◽  
Satellite Observations ◽  
Nox Emissions ◽  
Ozone Monitoring Instrument ◽  
Relative Contribution ◽  
Steady Decrease ◽  
The Us ◽  
Tropospheric No2 ◽  
Long Term Trends

Abstract. The National Emission Inventory (NEI) of the US Environmental Protection Agency (EPA) reports a steady decrease in US NOx emissions over the 2005–2017 period at a rate of 0.1 Tg N a−1 (53 % decrease over the period), reflecting sustained efforts to improve air quality. Tropospheric NO2 columns observed by the satellite-based Ozone Monitoring Instrument (OMI) over the US show a steady decrease until 2009 but a flattening afterward, which has been attributed to a flattening of NOx emissions, contradicting the NEI. We show here that the steady 2005–2017 decrease in NOx emissions reported by the NEI is in fact largely consistent with observed network trends of surface NO2 and ozone concentrations. The OMI NO2 trend is instead similar to that observed for nitrate wet deposition fluxes, which is weaker than that for anthropogenic NOx emissions, due to a large and increasing relative contribution of non-anthropogenic background sources of NOx (mainly lightning and soils). This is confirmed by contrasting OMI NO2 trends in urban winter, where the background is low and OMI NO2 shows a 2005–2017 decrease consistent with the NEI, and rural summer, where the background is high and OMI NO2 shows no significant 2005–2017 trend. A GEOS-Chem model simulation driven by NEI emission trends for the 2005–2017 period reproduces these different trends, except for the post-2009 flattening of OMI NO2, which we attribute to a model underestimate of free tropospheric NO2. Better understanding is needed of the factors controlling free tropospheric NO2 in order to relate satellite observations of tropospheric NO2 columns to the underlying NOx emissions and their trends. Focusing on urban winter conditions in the satellite data minimizes the effect of this free tropospheric background.

scholarly journals Using satellite observations of tropospheric NO<sub>2</sub> columns to infer long-term trends in US NO<sub>x</sub> emissions: the importance of accounting for the free tropospheric NO<sub>2</sub> background

2019 ◽  
Author(s):  
Rachel F. Silvern ◽  
Daniel J. Jacob ◽  
Loretta J. Mickley ◽  
Melissa P. Sulprizio ◽  
Katherine R. Travis ◽  
...  
Keyword(s):  
Environmental Protection Agency ◽  
Model Simulation ◽  
Satellite Observations ◽  
Nox Emissions ◽  
Ozone Monitoring Instrument ◽  
Relative Contribution ◽  
Steady Decrease ◽  
The Us ◽  
Tropospheric No2 ◽  
Long Term Trends

Abstract. The National Emission Inventory (NEI) of the US Environmental Protection Agency (EPA) reports a steady decrease of US NOx emissions over the 2005–2017 period at a rate of 0.1 Mt a−1 (53 % decrease over the period), reflecting sustained efforts to improve air quality. Tropospheric NO2 columns observed by the satellite-based Ozone Monitoring Instrument (OMI) over the US show a steady decrease until 2009 but a flattening afterward, which has been attributed to a flattening of NOx emissions in contradiction with the NEI. We show here that the steady 2005–2017 decrease of NOx emissions reported by the NEI is in fact consistent with observed network trends of surface NO2 and ozone concentrations. The OMI NO2 trend is instead similar to that observed for nitrate wet deposition fluxes, where post-2009 flattening is due to an increasing relative contribution of non-anthropogenic background (mainly lightning and soils) and not to a flattening of anthropogenic emissions. This is confirmed by contrasting OMI NO2 trends in urban winter, where the background is low and OMI NO2 shows a steady 2005–2017 decrease consistent with the NEI, and rural summer, where the background is high and OMI NO2 shows no significant 2005–2017 trend. A GEOS-Chem model simulation driven by NEI emission trends for the 2005–2017 period reproduces these different trends except for the post-2009 flattening of OMI NO2, which we attribute to a model underestimate of free tropospheric NO2. Better understanding is needed of the factors controlling free tropospheric NO2 in order to relate satellite observations of tropospheric NO2 columns to the underlying NOx emissions and their trends. Focusing on urban winter conditions in the satellite data minimizes the effect of this free tropospheric background.

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

2020 ◽  
Vol 20 (3) ◽  
pp. 1483-1495 ◽  
Author(s):  
Viral Shah ◽  
Daniel J. Jacob ◽  
Ke Li ◽  
Rachel F. Silvern ◽  
Shixian Zhai ◽  
...  
Keyword(s):  
Transport Model ◽  
Eastern China ◽  
Organic Nitrates ◽  
Nox Emissions ◽  
Chemical Transport Model ◽  
Ozone Monitoring Instrument ◽  
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 Ozone Monitoring Instrument (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 the 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. The 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 Top-Down NOX Emissions of European Cities Based on the Downwind Plume of Modelled and Space-Borne Tropospheric NO2 Columns

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2893 ◽  
Author(s):  
Willem W. Verstraeten ◽  
Klaas Folkert Boersma ◽  
John Douros ◽  
Jason E. Williams ◽  
Henk Eskes ◽  
...  
Keyword(s):  
Urban Areas ◽  
Transport Model ◽  
Nox Emissions ◽  
Inventory Data ◽  
Ozone Monitoring Instrument ◽  
Top Down ◽  
Chemistry Transport Model ◽  
European Cities ◽  
Tropospheric No2

Top-down estimates of surface NOX emissions were derived for 23 European cities based on the downwind plume decay of tropospheric nitrogen dioxide (NO2) columns from the LOTOS-EUROS (Long Term Ozone Simulation-European Ozone Simulation) chemistry transport model (CTM) and from Ozone Monitoring Instrument (OMI) satellite retrievals, averaged for the summertime period (April–September) during 2013. Here we show that the top-down NOX emissions derived from LOTOS-EUROS for European urban areas agree well with the bottom-up NOX emissions from the MACC-III inventory data (R2 = 0.88) driving the CTM demonstrating the potential of this method. OMI top-down NOX emissions over the 23 European cities are generally lower compared with the MACC-III emissions and their correlation is slightly lower (R2 = 0.79). The uncertainty on the derived NO2 lifetimes and NOX emissions are on average ~55% for OMI and ~63% for LOTOS-EUROS data. The downwind NO2 plume method applied on both LOTOS-EUROS and OMI tropospheric NO2 columns allows to estimate NOX emissions from urban areas, demonstrating that this is a useful method for real-time updates of urban NOX emissions with reasonable accuracy.

scholarly journals Evolution of SO2 and NOx Emissions from Several Large Combustion Plants in Europe during 2005–2015

2020 ◽  
Vol 17 (10) ◽  
pp. 3630 ◽  
Author(s):  
Daniel-Eduard Constantin ◽  
Corina Bocăneala ◽  
Mirela Voiculescu ◽  
Adrian Roşu ◽  
Alexis Merlaud ◽  
...  
Keyword(s):  
Power Plants ◽  
Standard Procedure ◽  
Air Pollutant ◽  
Satellite Observations ◽  
Pollutant Emissions ◽  
Nox Emissions ◽  
The European Union ◽  
Ozone Monitoring Instrument ◽  
Eu Directives ◽  
The Eu

The aim of this paper is to investigate the evolution of SO2 and NOx emissions of ten very large combustion plants (LCPs >500 MW) located in the European Union (EU) during 2005–2015. The evolution of NOx and SO2 emissions were analyzed against the EU Directives in force during 2005–2015. The investigation was performed using space-borne observations and estimated emissions collected from the EEA (European Environment Agency) inventory of air pollutant emissions. The power plants were chosen according to their capacity and emissions, located in various parts of Europe, to give an overall picture of atmospheric pollution with NOx and SO2 associated with the activity of very large LCPs in Europe. Satellite observations from OMI (Ozone Monitoring Instrument) are compared with calculated emissions in order to assess whether satellite observations can be used to monitor air quality, as a standard procedure, by governmental or nongovernmental institutions. Our results show that both space observations and estimated emissions of NOx and SO2 atmospheric content have a descending trend until 2010, complying with the EU Directives. The financial and economic crisis during 2007–2009 played an important role in reducing emissions.

scholarly journals NO<sub>x</sub> emissions, isoprene oxidation pathways, vertical mixing, and implications for surface ozone in the Southeast United States

2016 ◽  
Author(s):  
Katherine R. Travis ◽  
Daniel J. Jacob ◽  
Jenny A. Fisher ◽  
Patrick S. Kim ◽  
Eloise A. Marais ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Ozone ◽  
Vertical Mixing ◽  
Satellite Observations ◽  
Oxidation Products ◽  
Large Contribution ◽  
Nox Emissions ◽  
Tropospheric No2 ◽  
Isoprene Oxidation ◽  
Southeast Us

Abstract. Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx ≡ NO + NO2) and biogenic isoprene. Model estimates of surface ozone concentrations tend to be biased high in the region and this is of concern for designing effective emission control strategies to meet air quality standards. We use detailed chemical observations from the SEAC4RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model (CTM) at 0.25°×0.3125° horizontal resolution, to better understand the factors controlling surface ozone in the Southeast US. We find that the National Emission Inventory (NEI) for NOx from the US Environmental Protection Agency (EPA) is too high in the Southeast and nationally by 50 %. This is demonstrated by SEAC4RS observations of NOx and its oxidation products, by surface network observations of nitrate wet deposition fluxes, and by OMI satellite observations of tropospheric NO2 columns. Upper tropospheric NO2 from lightning makes a large contribution to the satellite observations that must be accounted for when using these data to estimate surface NOx emissions. Aircraft observations of upper tropospheric NO2 are higher than simulated by GEOS-Chem or expected from NO-NO2-O3 photochemical stationary state. NOx levels in the Southeast US are sufficiently low that only half of isoprene oxidation proceeds by the high-NOx pathway to produce ozone; this fraction is only moderately sensitive to changes in NOx emissions because isoprene and NOx emissions are spatially segregated. GEOS-Chem with reduced NOx emissions provides an unbiased simulation of ozone observations from the aircraft and from ozonesondes, and reproduces the observed ozone production efficiency in the boundary layer as derived from a regression of ozone and NOx oxidation products. However, the model is still biased high by 8 ± 13 ppb relative to observed surface ozone in the Southeast US. Ozonesondes launched during midday hours show a 7 ppb ozone decrease from 1.5 km to 0.2 km altitude, whereas GEOS-Chem has no such gradient because of efficient boundary layer mixing. We conclude that model biases in simulating surface ozone over the Southeast US may be due to a combination of excessive NOx emissions and excessive boundary layer vertical mixing.

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 The Spatial–Temporal Variation of Tropospheric NO2 over China during 2005 to 2018

Atmosphere ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 444 ◽  
Author(s):  
Chunjiao Wang ◽  
Ting Wang ◽  
Pucai Wang
Keyword(s):  
Eastern China ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
The North ◽  
Annual Range ◽  
Tropospheric No2 ◽  
Vertical Column Density ◽  
Long Term Trends ◽  
Increasing Trends ◽  
No2 Pollution

In recent years, new and strict air quality regulations have been implemented in China. Therefore, it is of great significance to evaluate the current air pollution situation and effectiveness of actions. In this study, Ozone Monitoring Instrument (OMI) satellite data were used to detect the spatiotemporal characteristics of tropospheric NO2 columns over China from 2005 to 2018, including spatial distribution, seasonal cycles and long-term trends. The averaged NO2 pollution is higher in southeastern China and lower in the northwest, which are well delineated by the Heihe–Tengchong line. Furthermore, the NO2 loadings are highest in the North China Plain, with vertical column density (VCD) exceeding 13 × 1015 molec cm−2. Regarding the seasonal cycle, the NO2 loadings in eastern China is highest in winter and lowest in summer, while the western region shows the opposite feature. The amplitude of annual range increase gradually from the south to the north. If the entire period of 2005–2018 is taken into account, China has experienced little change in NO2. In fact, however, there appears to be significant trends of an increase followed by a downward tendency, with the turning point in the year 2012. In the former episode of 2005–2012, increasing trends overwhelm nearly the whole nation, especially in the Jing–Jin–Tang region, Shandong Province, and Northern Henan and Southern Hebei combined regions, where the rising rates were as high as 1.0–1.8 × 1015 molec cm−2 year−1. In contrast, the latter episode of 2013–2018 features remarkable declines in NO2 columns over China. Particularly, the regions where the decreased degree was remarkable in 2013–2018 were consistent with the regions where the upward trend was obvious in 2005–2012. Overall, this upward–downward pattern is true for most parts of China. However, some of the largest metropolises, such as Beijing, Shanghai and Guangzhou, witnessed a continuous decrease in the NO2 amounts, indicating earlier and more stringent measures adopted in these areas. Finally, it can be concluded that China’s recent efforts to cut NO2 pollution are successful, especially in mega cities.

scholarly journals A methodology to constrain carbon dioxide emissions from coal-fired power plants using satellite observations of co-emitted nitrogen dioxide

2020 ◽  
Vol 20 (1) ◽  
pp. 99-116 ◽  
Author(s):  
Fei Liu ◽  
Bryan N. Duncan ◽  
Nickolay A. Krotkov ◽  
Lok N. Lamsal ◽  
Steffen Beirle ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Co2 Emissions ◽  
Co2 Emission ◽  
Power Plants ◽  
Operating Conditions ◽  
Satellite Observations ◽  
Nox Emissions ◽  
Bottom Up ◽  
Monitoring Instrument ◽  
The Us

Abstract. We present a method to infer CO2 emissions from individual power plants based on satellite observations of co-emitted nitrogen dioxide (NO2), which could serve as complementary verification of bottom-up inventories or be used to supplement these inventories. We demonstrate its utility on eight large and isolated US power plants, where accurate stack emission estimates of both gases are available for comparison. In the first step of our methodology, we infer nitrogen oxides (NOx) emissions from US power plants using Ozone Monitoring Instrument (OMI) NO2 tropospheric vertical column densities (VCDs) averaged over the ozone season (May–September) and a “top-down” approach that we previously developed. Second, we determine the relationship between NOx and CO2 emissions based on the direct stack emissions measurements reported by continuous emissions monitoring system (CEMS) programs, accounting for coal quality, boiler firing technology, NOx emission control device type, and any change in operating conditions. Third, we estimate CO2 emissions for power plants using the OMI-estimated NOx emissions and the CEMS NOx∕CO2 emission ratio. We find that the CO2 emissions estimated by our satellite-based method during 2005–2017 are in reasonable agreement with the US CEMS measurements, with a relative difference of 8 %±41 % (mean ± standard deviation). The broader implication of our methodology is that it has the potential to provide an additional constraint on CO2 emissions from power plants in regions of the world without reliable emissions accounting. We explore the feasibility by comparing the derived NOx∕CO2 emission ratios for the US with those from a bottom-up emission inventory for other countries and applying our methodology to a power plant in South Africa, where the satellite-based emission estimates show reasonable consistency with other independent estimates. Though our analysis is limited to a few power plants, we expect to be able to apply our method to more US (and world) power plants when multi-year data records become available from new OMI-like sensors with improved capabilities, such as the TROPOspheric Monitoring Instrument (TROPOMI), and upcoming geostationary satellites, such as the Tropospheric Emissions: Monitoring Pollution (TEMPO) instrument.

scholarly journals Novel application of satellite and in-situ measurements to map surface-level NO<sub>2</sub> in the Great Lakes region

2011 ◽  
Vol 11 (22) ◽  
pp. 11761-11775 ◽  
Author(s):  
C. J. Lee ◽  
J. R. Brook ◽  
G. J. Evans ◽  
R. V. Martin ◽  
C. Mihele
Keyword(s):  
Qualitative Data ◽  
Great Lakes Region ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
Surface Level ◽  
Suburban Areas ◽  
The Us ◽  
Tropospheric No2 ◽  
Vertical Column Density

Abstract. Ozone Monitoring Instrument (OMI) tropospheric NO2 vertical column density data were used in conjunction with in-situ NO2 concentrations collected by permanently installed monitoring stations to infer 24 h surface-level NO2 concentrations at 0.1° (~11 km) resolution. The region examined included rural and suburban areas, and the highly industrialised area of Windsor, Ontario, which is situated directly across the US-Canada border from Detroit, MI. Photolytic NO2 monitors were collocated with standard NO2 monitors to provide qualitative data regarding NOz interference during the campaign. The accuracy of the OMI-inferred concentrations was tested using two-week integrative NO2 measurements collected with passive monitors at 18 locations, approximating a 15 km grid across the region, for 7 consecutive two-week periods. When compared with these passive results, satellite-inferred concentrations showed an 18% positive bias. The correlation of the passive monitor and OMI-inferred concentrations (R=0.69, n=115) was stronger than that for the passive monitor concentrations and OMI column densities (R=0.52), indicating that using a sparse network of monitoring sites to estimate concentrations improves the direct utility of the OMI observations. OMI-inferred concentrations were then calculated for four years to show an overall declining trend in surface NO2 concentrations in the region. Additionally, by separating OMI-inferred surface concentrations by wind direction, clear patterns in emissions and affected down-wind regions, in particular around the US-Canada border, were revealed.

scholarly journals NO<sub><i>x</i></sub> emission estimates during the 2014 Youth Olympic Games in Nanjing

2015 ◽  
Vol 15 (16) ◽  
pp. 9399-9412 ◽  
Author(s):  
J. Ding ◽  
R. J. van der A ◽  
B. Mijling ◽  
P. F. Levelt ◽  
N. Hao
Keyword(s):  
Air Quality ◽  
Olympic Games ◽  
Transport Model ◽  
Satellite Observations ◽  
Strong Increase ◽  
Nox Emissions ◽  
Chemical Transport Model ◽  
Ozone Monitoring Instrument ◽  
Spring Festival ◽  
Emission Estimate

Abstract. The Nanjing Government applied temporary environmental regulations to guarantee good air quality during the Youth Olympic Games (YOG) in 2014. We study the effect of those regulations by applying the emission estimate algorithm DECSO (Daily Emission estimates Constrained by Satellite Observations) to measurements of the Ozone Monitoring Instrument (OMI). We improved DECSO by updating the chemical transport model CHIMERE from v2006 to v2013 and by adding an Observation minus Forecast (OmF) criterion to filter outlying satellite retrievals due to high aerosol concentrations. The comparison of model results with both ground and satellite observations indicates that CHIMERE v2013 is better performing than CHIMERE v2006. After filtering the satellite observations with high aerosol loads that were leading to large OmF values, unrealistic jumps in the emission estimates are removed. Despite the cloudy conditions during the YOG we could still see a decrease of tropospheric NO2 column concentrations of about 32 % in the OMI observations when compared to the average NO2 columns from 2005 to 2012. The results of the improved DECSO algorithm for NOx emissions show a reduction of at least 25 % during the YOG period and afterwards. This indicates that air quality regulations taken by the local government have an effect in reducing NOx emissions. The algorithm is also able to detect an emission reduction of 10 % during the Chinese Spring Festival. This study demonstrates the capacity of the DECSO algorithm to capture the change of NOx emissions on a monthly scale. We also show that the observed NO2 columns and the derived emissions show different patterns that provide complimentary information. For example, the Nanjing smog episode in December 2013 led to a strong increase in NO2 concentrations without an increase in NOx emissions. Furthermore, DECSO gives us important information on the non-trivial seasonal relation between NOx emissions and NO2 concentrations on a local scale.

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