L. N. Lamsal

Universities Space Research Association, Houston, Texas, United States

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Publications (50)104.38 Total impact

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    ABSTRACT: A method is developed to estimate global NO2 and SO2 dry deposition fluxes at high spatial resolution (0.1° × 0.1°) using satellite measurements from the Ozone Monitoring Instrument (OMI) on the Aura satellite, in combination with simulations from the GEOS-Chem global chemical transport model. These global maps for 2005–2007 provide a dataset for use in examining global and regional budgets of deposition. In order to properly assess SO2 on a global scale, a method is developed to account for the geospatial character of background offsets in retrieved satellite columns. Globally, annual dry deposition to land estimated from OMI as NO2 contributes 1.5 ± 0.5 Tg of nitrogen and as SO2 contributes 13.7 ± 4.0 Tg of sulfur. Differences between OMI-inferred NO2 dry deposition fluxes and those of other models and observations vary from excellent agreement to an order of magnitude difference, with OMI typically on the low end of estimates. SO2 dry deposition fluxes compare well with in situ CASTNET-network-inferred flux over North America (slope = 0.98, r = 0.71). The most significant NO2 dry deposition flux to land per area occurs in the Pearl River Delta, China at 13.9 kg N ha−1 yr−1, while SO2 dry deposition has a global maximum rate of 72.0 kg S ha−1 yr−1 to the east of Jinan in China's Shandong province. Dry deposition fluxes are explored in several urban areas, where NO2 contributes on average 9–36% and as much as 85% of total NOy dry deposition.
    Global Biogeochemical Cycles. 09/2014;
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    ABSTRACT: Satellite data of atmospheric pollutants are becoming more widely used in the decision-making and environmental management activities of public, private sector and non-profit organizations. They are employed for estimating emissions, tracking pollutant plumes, supporting air quality forecasting activities, providing evidence for “exceptional event” declarations, monitoring regional long-term trends, and evaluating air quality model output. However, many air quality managers are not taking full advantage of the data for these applications nor has the full potential of satellite data for air quality applications been realized. A key barrier is the inherent difficulties associated with accessing, processing, and properly interpreting observational data. A degree of technical skill is required on the part of the data end-user, which is often problematic for air quality agencies with limited resources. Therefore, we 1) review the primary uses of satellite data for air quality applications, 2) provide some background information on satellite capabilities for measuring pollutants, 3) discuss the many resources available to the end-user for accessing, processing, and visualizing the data, and 4) provide answers to common questions in plain language.
    Atmospheric Environment 09/2014; · 3.11 Impact Factor
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    ABSTRACT: To investigate the ability of column (or partial column) information to represent surface air quality, results of linear regression analyses between surface mixing ratio data and column abundances for O3 and NO2 are presented for the July 2011 Maryland deployment of the DISCOVER-AQ mission. Data collected by the P-3B aircraft, ground-based Pandora spectrometers, Aura/OMI satellite instrument, and simulations for July 2011 from the CMAQ air quality model during this deployment provide a large and varied data set, allowing this problem to be approached from multiple perspectives. O3 columns typically exhibited a statistically significant and high degree of correlation with surface data (R2 > 0.64) in the P-3B data set, a moderate degree of correlation (0.16 < R2 < 0.64) in the CMAQ data set, and a low degree of correlation (R2 < 0.16) in the Pandora and OMI data sets. NO2 columns typically exhibited a low to moderate degree of correlation with surface data in each data set. The results of linear regression analyses for O3 exhibited smaller errors relative to the observations than NO2 regressions. These results suggest that O3 partial column observations from future satellite instruments with sufficient sensitivity to the lower troposphere can be meaningful for surface air quality analysis.
    Atmospheric Environment 08/2014; 92:429–441. · 3.11 Impact Factor
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    ABSTRACT: Satellite remote sensing is increasingly being used to monitor air quality over localized sources such as the Canadian oil sands. Following an initial study, significantly low biases have been identified in current NO2 and SO2 retrieval products from the Ozone Monitoring Instrument (OMI) satellite sensor over this location resulting from a combination of its rapid development and small spatial scale. Air mass factors (AMFs) used to convert line-of-sight "slant" columns to vertical columns were re-calculated for this region based on updated and higher resolution input information including absorber profiles from a regional-scale (15 km × 15 km resolution) air quality model, higher spatial and temporal resolution surface reflectivity, and an improved treatment of snow. The overall impact of these new Environment Canada (EC) AMFs led to substantial increases in the peak NO2 and SO2 average vertical column density (VCD), occurring over an area of intensive surface mining, by factors of 2 and 1.4, respectively, relative to estimates made with previous AMFs. Comparisons are made with long-term averages of NO2 and SO2 (2005-2011) from in situ surface monitors by using the air quality model to map the OMI VCDs to surface concentrations. This new OMI-EC product is able to capture the spatial distribution of the in situ instruments (slopes of 0.65 to 1.0, correlation coefficients of >0.9). The concentration absolute values from surface network observations were in reasonable agreement, with OMI-EC NO2 and SO2 biased low by roughly 30%. Several complications were addressed including correction for the interference effect in the surface NO2 instruments and smoothing and clear-sky biases in the OMI measurements. Overall these results highlight the importance of using input information that accounts for the spatial and temporal variability of the location of interest when performing retrievals.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 03/2014; 14(7). · 5.51 Impact Factor
  • Atmospheric Environment. 01/2014;
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    ABSTRACT: Particulate organic matter is of interest for air quality and climate research, but the relationship between ambient organic mass (OM) and organic carbon (OC) remains ambiguous both in measurements and in modeling. We present a simple method to derive an estimate of the spatially and seasonally resolved global, lower tropospheric, ratio between OM and OC. We assume ambient NO2 concentrations as a surrogate for fresh emission which mostly determines the continental scale OM/OC ratio. For this, we first develop a parameterization for the OM/OC ratio using the primary organic aerosol (POA) fraction of total OM estimated globally from Aerosol Mass Spectrometer (AMS) measurements, and evaluate it with high mass resolution AMS data. Second, we explore the ability of ground-level NO2 concentrations derived from the OMI satellite sensor to serve as a proxy for fresh emissions that have a high POA fraction, and apply NO2 data to derive ambient POA fraction. The combination of these two methods yields an estimate of OM/OC from NO2 measurements. Although this method has inherent deficiencies over biomass burning, free-tropospheric, and marine environments, elsewhere it offers more information than the currently used global-mean OM/OC ratios. The OMI-derived global OM/OC ratio ranges from 1.3 to 2.1 (μg/μgC), with distinct spatial variation between urban and rural regions. The seasonal OM/OC ratio has a summer maximum and a winter minimum over regions dominated by combustion emissions. This dataset serves as a tool for interpreting organic carbon measurements, and for evaluating modeling of atmospheric organics. We also develop an additional parameterization for models to estimate the ratio of primary OM to OC from simulated NOx concentrations.
    Atmospheric Environment. 01/2014; 87:34–40.
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    W. Tang, D. S. Cohan, L. N. Lamsal, X. Xiao, W. Zhou
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    ABSTRACT: Inverse modeling of nitrogen oxide (NOx) emissions using satellite-based NO2 observations has become more prevalent in recent years, but has rarely been applied to regulatory modeling at regional scales. In this study, OMI satellite observations of NO2 column densities are used to conduct inverse modeling of NOx emission inventories for two Texas State Implementation Plan (SIP) modeling episodes. Addition of lightning, aircraft, and soil NOx emissions to the regulatory inventory narrowed but did not close the gap between modeled and satellite-observed NO2 over rural regions. Satellite-based top-down emission inventories are created with the regional Comprehensive Air Quality Model with extensions (CAMx) using two techniques: the direct scaling method and discrete Kalman filter (DKF) with decoupled direct method (DDM) sensitivity analysis. The simulations with satellite-inverted inventories are compared to the modeling results using the a priori inventory as well as an inventory created by a ground-level NO2-based DKF inversion. The DKF inversions yield conflicting results: the satellite-based inversion scales up the a priori NOx emissions in most regions by factors of 1.02 to 1.84, leading to 3-55% increase in modeled NO2 column densities and 1-7 ppb increase in ground 8 h ozone concentrations, while the ground-based inversion indicates the a priori NOx emissions should be scaled by factors of 0.34 to 0.57 in each region. However, none of the inversions improve the model performance in simulating aircraft-observed NO2 or ground-level ozone (O3) concentrations.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 11/2013; 13(21):11005-11018. · 5.51 Impact Factor
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    ABSTRACT: Concern is growing about the effects of urbanization on air pollution and health. Nitrogen dioxide (NO2) released primarily from combustion processes such as traffic is a short-lived atmospheric pollutant that serves as an air quality indicator, and is itself a health concern. We derive a global distribution of ground-level NO2 concentrations from tropospheric NO2 columns retrieved from the OMI satellite instrument. Local scaling factors from a three-dimensional chemistry-transport model (GEOS-Chem) are used to relate the OMI NO2 columns to ground-level concentrations. The OMI-derived surface NO2 data are significantly correlated (r=0.69) with in situ surface measurements. We examine how the OMI-derived ground-level NO2 concentrations, OMI NO2 columns, and bottom-up NOx emission inventories relate to urban population. Emission hot spots such as power plants are excluded to focus on urban relationships. The correlation of surface NO2 with population is significant for the three countries and one continent examined here: United States (r=0.71), Europe (r=0.67), China (r=0.69) and India (r=0.59). Urban NO2 pollution, like other urban properties, is a power law scaling function of the population size: NO2 concentration increases proportional to population raised to an exponent. The value of the exponent varies by region from 0.36 for India to 0.66 for China reflecting regional differences in industrial development and per capita emissions. It has been generally established that energy efficiency increases and therefore per capita NOx emissions decrease with urban population; here we show how outdoor ambient NO2 concentrations depend upon urban population in different global regions.
    Environmental Science & Technology 06/2013; · 5.48 Impact Factor
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    ABSTRACT: We describe a new algorithm for the retrieval of nitrogen dioxide (NO2) vertical columns from nadir-viewing satellite instruments. This algorithm (SP2) is the basis for the Version 2.1 OMI NO2 Standard Product and features a novel method for separating the stratospheric and tropospheric columns. The approach estimates the stratospheric NO2 directly from satellite data without using stratospheric chemical transport models or assuming any global zonal wave pattern. Tropospheric NO2 columns are retrieved using air mass factors derived from high-resolution radiative transfer calculations and a monthly climatology of NO2 profile shapes. We also present details of how uncertainties in the retrieved columns are estimated. The sensitivity of the retrieval to assumptions made in the stratosphere-troposphere separation is discussed and shown to be small, in an absolute sense, for most regions. We compare daily and monthly mean global OMI NO2 retrievals using the SP2 algorithm with those of the original Version 1 Standard Product (SP1) and the Dutch DOMINO product. The SP2 retrievals yield significantly smaller summertime tropospheric columns than SP1 and are relatively free of modeling artifacts and negative tropospheric NO2 values. In a re-analysis of an INTEX-B validation study, we show that SP2 largely eliminates a ∼20% discrepancy that existed between OMI and independent in situ springtime NO2 SP1 measurements.
    Atmospheric Measurement Techniques 02/2013; 6(1):1361-1407. · 3.21 Impact Factor
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    Environmental Science & Technology 08/2012; 46(16):8523-4. · 5.48 Impact Factor
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    ABSTRACT: Comparative studies between results from the CARIBIC airborne DOAS instrument on board of CARIBIC and satellite observations are presented. CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container, www.caribic.de) observes physical and chemical processes in the earth’s atmosphere using a fully automated measurement container aboard a Lufthansa Airbus 340-600. A special inlet system is mounted underneath the aeroplane with probes for trace gases, water vapour and aerosol particles. It also includes three telescopes of a DOAS (Differential Optical Absorption Spectroscopy) system for remote sensing. Enhanced sulphur dioxide (SO2) column densities were observed by CARIBIC DOAS after the eruptions of Kasatochi (Alaska, USA) and Eyjafjallajökull (Iceland) as well as downwind of the nickel smelter in Norilsk (Siberia). For all cases detailed studies were performed and the data were used for comparisons with products from several satellite instruments. To reduce the additional uncertainty caused by trajectory calculation, the satellite with the shortest time difference relative to the CARIBIC observation was validated. For the Kasatochi plume wind speeds were relevant for the comparison in view of a discrepancy in the timing of aeroplane and satellite overpass. In the case of a dedicated flight designed to intercept parts of the Eyjafjallajökull plume, also Bromine Monoxide (BrO) was detected. Due to high noise in both CARIBIC and GOME-2 (Global Ozone Monitoring Experiment) data a qualitative comparison of the BrO vertical column densities was not performed. For Norilsk, where NO2 enhancements were also detected, wind data were used to estimate the SO2 flux. The flux estimate based on CARIBIC data was in a good agreement with independent data including OMI (Ozone Monitoring Instrument) based results. In general, good agreement between CARIBIC and the satellite data was obtained.
    ATMOS 2012 – Advances in Atmospheric Science and Applications; 06/2012
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    ABSTRACT: Using OMI (Ozone Monitoring Instrument) tropospheric NO2 columns and a nested-grid 3-D global chemical transport model (GEOS-Chem), we investigated the growth in NOx emissions from coal-fired power plants and their contributions to the growth in NO2 columns in 2005-2007 in China. We first developed a unit-based power plant NOx emission inventory for 2005-2007 to support this investigation. The total capacities of coal-fired power generation have increased by 48.8% in 2005-2007, with 92.2% of the total capacity additions coming from generator units with size ≥300 MW. The annual NOx emissions from coal-fired power plants were estimated to be 8.11 Tg NO2 for 2005 and 9.58 Tg NO2 for 2007, respectively. The modeled summer average tropospheric NO2 columns were highly correlated (R2 = 0.79-0.82) with OMI measurements over grids dominated by power plant emissions, with only 7-14% low bias, lending support to the high accuracy of the unit-based power plant NOx emission inventory. The ratios of OMI-derived annual and summer average tropospheric NO2 columns between 2007 and 2005 indicated that most of the grids with significant NO2 increases were related to power plant construction activities. OMI had the capability to trace the changes of NOx emissions from individual large power plants in cases where there is less interference from other NOx sources. Scenario runs from GEOS-Chem model suggested that the new power plants contributed 18.5% and 10% to the annual average NO2 columns in 2007 in Inner Mongolia and North China, respectively. The massive new power plant NOx emissions significantly changed the local NO2 profiles, especially in less polluted areas. A sensitivity study found that changes of NO2 shape factors due to including new power plant emissions increased the summer average OMI tropospheric NO2 columns by 3.8-17.2% for six selected locations, indicating that the updated emission information could help to improve the satellite retrievals.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 05/2012; 12(10):4429-4447. · 5.51 Impact Factor
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    ABSTRACT: Few epidemiological studies of air pollution have used residential histories to develop long-term retrospective exposure estimates for multiple ambient air pollutants and vehicle and industrial emissions. We present such an exposure assessment for a Canadian population-based lung cancer case-control study of 8353 individuals using self-reported residential histories from 1975 to 1994. We also examine the implications of disregarding and/or improperly accounting for residential mobility in long-term exposure assessments. National spatial surfaces of ambient air pollution were compiled from recent satellite-based estimates (for PM2.5 and NO2) and a chemical transport model (for O3). The surfaces were adjusted with historical annual air pollution monitoring data, using either spatiotemporal interpolation or linear regression. Model evaluation was conducted using an independent ten percent subset of monitoring data per year. Proximity to major roads, incorporating a temporal weighting factor based on Canadian mobile-source emission estimates, was used to estimate exposure to vehicle emissions. A comprehensive inventory of geocoded industries was used to estimate proximity to major and minor industrial emissions. Calibration of the national PM2.5 surface using annual spatiotemporal interpolation predicted historical PM2.5 measurement data best (R2 = 0.51), while linear regression incorporating the national surfaces, a time-trend and population density best predicted historical concentrations of NO2 (R2 = 0.38) and O3 (R2 = 0.56). Applying the models to study participants residential histories between 1975 and 1994 resulted in mean PM2.5, NO2 and O3 exposures of 11.3 μg/m3 (SD = 2.6), 17.7 ppb (4.1), and 26.4 ppb (3.4) respectively. On average, individuals lived within 300 m of a highway for 2.9 years (15% of exposure-years) and within 3 km of a major industrial emitter for 6.4 years (32% of exposure-years). Approximately 50% of individuals were classified into a different PM2.5, NO2 and O3 exposure quintile when using study entry postal codes and spatial pollution surfaces, in comparison to exposures derived from residential histories and spatiotemporal air pollution models. Recall bias was also present for self-reported residential histories prior to 1975, with cases recalling older residences more often than controls. We demonstrate a flexible exposure assessment approach for estimating historical air pollution concentrations over large geographical areas and time-periods. In addition, we highlight the importance of including residential histories in long-term exposure assessments. For submission to: Environmental Health.
    Environmental Health 04/2012; 11:22. · 2.71 Impact Factor
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    ABSTRACT: Based on a case-study of the nickel smelter in Norilsk (Siberia), the retrieval of trace gas fluxes using airborne remote sensing is discussed. CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container, www.caribic.de) observes physical and chemical processes in the atmosphere using a fully automated measurement container aboard a Lufthansa Airbus 340-600. A special inlet system is mounted on the aircraft with probes for trace gases, water vapor and aerosol particles. The inlet system also includes DOAS (Differential Optical Absorption Spectroscopy) telescopes for remote sensing. In October 2010, enhanced NO2 and high SO2 Slant Column Densities up to 6 · 1017 molec/cm2 were detected near Norilsk with the nadir channel of the DOAS instrument. The retrieved column densities were combined with ECMWF wind data to derive the SO2 flux crossing the vertical plane of the flight route. With that, the SO2 output of the Norilsk industrial complex is estimated to be ~1 Mt per year, which is in agreement with various independent estimates. We also compare our value to results obtained using data from satellite remote sensing (GOME-2, OMI). The validity of the assumptions we used to obtain our estimate is discussed. We also discuss the adaption of our method to other gases and sources like the NO2 emissions of industrial complexes or major cities.
    Journal of Geophysical Research Atmospheres 04/2012; 117(D11):5629-. · 3.44 Impact Factor
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    ABSTRACT: Nitrogen oxides (NOx) are key actors in air quality and climate change. Satellite remote sensing of tropospheric NO2has developed rapidly with enhanced spatial and temporal resolution since initial observations in 1995. We have developed an improved algorithm and retrieved tropospheric NO2 columns from Ozone Monitoring Instrument. Column observations of tropospheric NO2 from the nadir-viewing satellite sensors contain large contributions from the boundary layer due to strong enhancement of NO2 in the boundary layer. We infer ground-level NO2 concentrations from the OMI satellite instrument which demonstrate significant agreement with in-situ surface measurements. We examine how NO2 columns measured by satellite, ground-level NO2 derived from satellite, and NOx emissions obtained from bottom-up inventories relate to world's urban population. We perform inverse modeling analysis of NO2 measurements from OMI to estimate "top-down" surface NOx emissions, which are used to evaluate and improve "bottom-up" emission inventories. We use NO2 column observations from OMI and the relationship between NO2 columns and NOxemissions from a GEOS-Chem model simulation to estimate the annual change in bottom-up NOx emissions. The emission updates offer an improved estimate of NOx that are critical to our understanding of air quality, acid deposition, and climate change.
    04/2012;
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    ABSTRACT: Using OMI (Ozone Monitoring Instrument) tropospheric NO2 columns and a nested-grid 3-D global chemical transport model (GEOS-Chem), we investigated the growth in NOx emissions from coal-fired power plants and their contributions to the growth in NO2 columns in 2005-2007 in China. We first developed a unit-based power plant NOx emission inventory for 2005-2007 to support this investigation. The total capacities of coal-fired power generation have increased by 48.8% in 2005-2007, with 92.2% of the total capacity additions coming from generator units with size ≥300 MW. The annual NOx emissions from coal-fired power plants were estimated to be 8.11 Tg NO2 for 2005 and 9.58 Tg NO2 for 2007, respectively. The modeled summer average tropospheric NO2 columns were highly correlated (R2 = 0.79-0.82) with OMI measurements over grids dominated by power plant emissions, with only 7-14% low bias, lending support to the high accuracy of the unit-based power plant NOx emission inventory. The ratios of OMI-derived annual and summer average tropospheric NO2 columns between 2007 and 2005 indicated that most of the grids with significant NO2 increases were related to power plant construction activities. OMI had the capability to trace the changes of NOx emissions from individual large power plants in cases where there is less interference from other NOx sources. Scenario runs from GEOS-Chem model suggested that the new power plants contributed 18.5% and 10% to the annual average NO2 columns in 2007 in Inner Mongolia and North China, respectively. The massive new power plant NOx emissions significantly changed the local NO2 profiles, especially in less polluted areas. A sensitivity study found that changes of NO2 shape factors due to including new power plant emissions increased the summer average OMI tropospheric NO2 columns by 3.8-17.2% for six selected locations, indicating that the updated emission information could help to improve the satellite retrievals.
    Atmospheric Chemistry and Physics 01/2012; 12(1):45-91. · 4.88 Impact Factor
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    ABSTRACT: Nitrogen oxides are key actors in air quality and climate change. Column observations of tropospheric NO2 from the nadir-veiwing satellite sensors have been widely used to understand sources and chemistry of NOx. We have implemented several improvements to the operational algorithm developed at NASA GSFC and retrieved tropospheric NO2. Here we evaluate the new product using in situ surface measurements at the SEARCH, AQS/EPA, and NAPS networks, in situ aircraft (DISCOVER-AQ and RAMMPP), and ground-based PANDORA and DOAS measurements. The agreement among these data is within the uncertainty of measurements. The new OMI tropospheric NO2 product available at high spatial resolution is valuable to evaluate chemical transport models, to examine spatial and temporal pattern of NOx emissions, to provide top-down constraints to surface NOx emissions, and to estimate NOx lifetimes.
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: Much progress has been made in trying to create satellite products for tracking the important pollutants ozone and NO2 in the troposphere. Yet, in mid-latitude regions where meteorological interactions with pollutants are complex, accuracy can be difficult to achieve, largely due to rapid changes and persistent layering of some constituents. Comparisons of TTOR ozone and satellite NO2 with ground-truth are presented, mostly from the mid-Atlantic coastal area. Examples of the complexity of retrieving tropospheric ozone column amounts are illustrated with soundings and aircraft profiles from campaigns in the past several years, including the July 2011 DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality).
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: Nitrogen dioxide (NO2) is an atmospheric trace gas, important in the chemistries of both stratospheric ozone and tropospheric pollution. We describe a new technique for retrieving NO2 vertical columns from nadir-viewing satellite instruments and apply it to the measurements from the Dutch-Finnish Ozone Monitoring Instrument (OMI) on board NASA Aura satellite. The algorithm, now operational at NASA, is a significant advance over the previous version, and includes a greatly improved stratospheric-tropospheric partition estimation that uses minimal model inputs, as well as seasonally dependent a priori NO2 profile shapes for better air mass factor calculations. These improvements greatly reduce biases noted in previous validation studies. We show a comparison of the new tropospheric NO2 columns against other satellite retrievals and present validation results, including a re-analysis of the Intercontinental Chemical Transport Experiment (INTEX-B).
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: Nitrogen dioxide (NO2) is a short-lived atmospheric pollutant released from combustion processes and is an indicator of air quality. We derive a global distribution of ground-level NO2 concentrations by applying local scaling factors from a global three-dimensional model to tropospheric NO2 columns retrieved from the Ozone Monitoring Instrument. The OMI-derived surface NO2 data are compared with in situ surface NO2 data obtained from the SEARCH, AQS/EPA, and NAPS networks. The correlation between the OMI-derived surface NO2 and the ground-based measurements is generally > 0.5. We examine how NO2 columns measured by satellite, ground-level NO2 derived from satellite, and NOx emissions obtained from bottom-up inventories relate to city population in North America, Europe, and Asia. NO2 increases proportional to population raised to an exponent that is in the range 0.25-0.55. This relationship provides insights into per capita emissions and the quality of air people breathe.
    AGU Fall Meeting Abstracts. 12/2011;

Publication Stats

389 Citations
104.38 Total Impact Points

Institutions

  • 2012–2014
    • Universities Space Research Association
      Houston, Texas, United States
  • 2007–2011
    • Dalhousie University
      • Department of Physics and Atmospheric Science
      Halifax, Nova Scotia, Canada
  • 1620–2005
    • Universität Bremen
      • Institut für Umweltphysik (IUP)
      Bremen, Bremen, Germany