The Experts below are selected from a list of 81 Experts worldwide ranked by ideXlab platform
Daniel J Jacob - One of the best experts on this subject based on the ideXlab platform.
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transpacific transport of ozone pollution and the effect of recent asian emission increases on air quality in north america an integrated analysis using satellite aircraft ozonesonde and surface observations
Atmospheric Chemistry and Physics, 2008Co-Authors: Lin Zhang, Daniel J Jacob, Daniel A. Jaffe, Anne M. Thompson, K F Boersma, J R Olson, Kevin W Bowman, J Worden, Melody A AveryAbstract:We use an ensemble of aircraft, satellite, sonde, and surface observations for April–May 2006 (NASA/INTEX-B aircraft campaign) to better understand the mechanisms for transpacific ozone pollution and its implications for North American air quality. The observations are interpreted with a global 3-D chemical transport model (GEOS-Chem). OMI NO 2 satellite observations constrain Asian anthropogenic NO x emissions and indicate a factor of 2 increase from 2000 to 2006 in China. Satellite observations of CO from AIRS and TES indicate two major events of Asian transpacific pollution during INTEX-B. Correlation between TES CO and ozone observations shows evidence for transpacific ozone pollution. The semi-permanent Pacific High and Aleutian Low cause splitting of transpacific pollution plumes over the Northeast Pacific. The northern branch circulates around the Aleutian Low and has little impact on North America. The southern branch circulates around the Pacific High and some of that air impacts western North America. Both aircraft measurements and model results show sustained ozone production driven by Peroxyacetylnitrate (PAN) decomposition in the southern branch, roughly doubling the transpacific influence from ozone produced in the Asian boundary layer. Model simulation of ozone observations at Mt. Bachelor Observatory in Oregon (2.7 km altitude) indicates a mean Asian ozone pollution contribution of 9±3 ppbv to the mean observed concentration of 54 ppbv, reflecting mostly an enhancement in background ozone rather than episodic Asian plumes. Asian pollution enhanced surface ozone concentrations by 5–7 ppbv over western North America in spring 2006. The 2000–2006 rise in Asian anthropogenic emissions increased this influence by 1–2 ppbv.
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ozone production in transpacific asian pollution plumes and implications for ozone air quality in california
Journal of Geophysical Research, 2004Co-Authors: R C Hudman, Daniel J Jacob, Colette L Heald, O R Cooper, M J Evans, Rokjin J Park, F C Fehsenfeld, F Flocke, J S HollowayAbstract:[1] We examine the ozone production efficiency in transpacific Asian pollution plumes, and the implications for ozone air quality in California, by using aircraft and surface observations in April–May 2002 from the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) campaign off the California coast and the Pacific Exploration of Asian Continental Emission–B (PEACE-B) campaign over the northwest Pacific. The observations are interpreted with a global three-dimensional chemical transport model (GEOS-CHEM). The model reproduces the mean features observed for CO, reactive nitrogen oxides (NOy), and ozone but underestimates the strong (20 ppbv) stratospheric contribution to ozone in the middle troposphere. The ITCT 2K2 aircraft sampled two major transpacific Asian pollution plumes, one on 5 May at 5–8 km altitude with CO up to 275 ppbv but no elevated ozone and one on 17 May at 2.5–4 km altitude with CO up to 225 ppbv and ozone up to 90 ppbv. We show that the elevated ozone in the latter plume is consistent with production from Peroxyacetylnitrate (PAN) decomposition during subsidence of the plume over the northeast Pacific. This production is particularly efficient because of the strong radiation and low humidity of the subsiding environment. We argue that such PAN decomposition represents a major and possibly dominant component of the ozone enhancement in transpacific Asian pollution plumes. Strong dilution of Asian pollution plumes takes place during entrainment in the U.S. boundary layer, greatly reducing their impact at U.S. surface sites. California mountain sites are more sensitive to Asian pollution because of their exposure to the free troposphere. Model results indicate a mean Asian pollution enhancement of 7 ppbv ozone at Sequoia National Park in May 2002 on those days when the 8-hour average ozone concentration exceeded 80 ppbv. INDEX TERMS: 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); KEYWORDS: ozone, Asian pollution, ITCT 2K2, PEACE-B, transpacific transport
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export of noy from the north american boundary layer reconciling aircraft observations and global model budgets
Journal of Geophysical Research, 2004Co-Authors: Daniel J Jacob, Robert M Yantosca, William J Munger, David ParrishAbstract:[1] Fossil fuel combustion accounts for >50% of the global atmospheric emission of NOx, but this source is concentrated in the polluted continental boundary layer (CBL) and only a small fraction is exported as NOy (NOx and its oxidation products) to the global troposphere. Better quantification of this export efficiency is needed because of its implications for global tropospheric ozone. A recent Lagrangian analysis of the NOy-CO correlations observed from the North Atlantic Regional Experiment in September 1997 (NARE'97) aircraft campaign downwind of eastern North America (September 1997) indicated a NOy export efficiency of <10%, with <10% of the exported NOy present as NOx. In contrast, previous three-dimensional (3-D) model Eulerian budget analyses for the North American boundary layer indicated NOy export efficiencies of 25–30%, with 30–35% of the exported NOy present as NOx. We investigated this apparent discrepancy by simulating the NARE'97 aircraft observations with a global 3-D model of tropospheric chemistry (GEOS-CHEM) and using the model to calculate the NOy export efficiency both through a Lagrangian analysis of the NOy-CO correlations along the aircraft flight tracks and through an Eulerian budget analysis for the North American boundary layer. The model reproduces the variability and NOy-CO correlations observed in the aircraft data and also at the Harvard Forest surface site in the northeastern United States. We show that the previous Lagrangian analyses of the NOy export efficiency during NARE'97 were probably biased low because of underestimation of the CO background. Correcting for this bias, we find a NOy export efficiency of 17 ± 7% in the model and 15 ± 11% in the observations. A similar NOy export efficiency (20%) in the model is obtained from the Eulerian budget analysis, demonstrating that the Lagrangian and Eulerian approaches are in fact consistent. Export efficiencies of NOy in previous 3-D model Eulerian budget analyses were probably too high because of insufficient scavenging out of the CBL. Model results indicate that only 6% of the exported NOy is present as NOx along the aircraft flight tracks, in agreement with the observations, but that 40% of the NOy export flux is present as NOx, in agreement with the previous 3-D model analyses. This result reflects the fast oxidation of NOx between the point of exit from the CBL and the point of sampling by the aircraft. The eventual ozone production in the global troposphere due to exported NOx and Peroxyacetylnitrate (PAN), with equal contributions from each, is comparable in magnitude to the direct export of ozone pollution from the North American boundary layer.
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asian outflow and trans pacific transport of carbon monoxide and ozone pollution an integrated satellite aircraft and model perspective
Journal of Geophysical Research, 2003Co-Authors: Colette L Heald, Daniel J Jacob, Arlene M Fiore, L K Emmons, John C Gille, M N Deeter, Juying Warner, D P Edwards, J H Crawford, A J HamlinAbstract:[1] Satellite observations of carbon monoxide (CO) from the Measurements of Pollution in the Troposphere (MOPITT) instrument are combined with measurements from the Transport and Chemical Evolution Over the Pacific (TRACE-P) aircraft mission over the northwest Pacific and with a global three-dimensional chemical transport model (GEOS-CHEM) to quantify Asian pollution outflow and its trans-Pacific transport during spring 2001. Global CO column distributions in MOPITT and GEOS-CHEM are highly correlated (R2 = 0.87), with no significant model bias. The largest regional bias is over Southeast Asia, where the model is 18% too high. A 60% decrease of regional biomass burning emissions in the model (to 39 Tg yr−1) would correct the discrepancy; this result is consistent with TRACE-P observations. MOPITT and TRACE-P also give consistent constraints on the Chinese source of CO from fuel combustion (181 Tg CO yr−1). Four major events of trans-Pacific transport of Asian pollution in spring 2001 were seen by MOPITT, in situ platforms, and GEOS-CHEM. One of them was sampled by TRACE-P (26–27 February) as a succession of pollution layers over the northeast Pacific. These layers all originated from one single event of Asian outflow that split into northern and southern plumes over the central Pacific. The northern plume (sampled at 6–8 km off California) had no ozone enhancement. The southern subsiding plume (sampled at 2–4 km west of Hawaii) contained a 8–17 ppbv ozone enhancement, driven by decomposition of Peroxyacetylnitrate (PAN) to nitrogen oxides (NOx). This result suggests that PAN decomposition in trans-Pacific pollution plumes subsiding over the United States could lead to significant enhancements of surface ozone.
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global modeling of tropospheric chemistry with assimilated meteorology model description and evaluation
Journal of Geophysical Research, 2001Co-Authors: Isabelle Bey, Daniel J Jacob, Jennifer A Logan, Arlene M Fiore, Robert M Yantosca, Brendan D Field, Honguy Y Liu, Loretta J Mickley, Martin G. SchultzAbstract:We present a first description and evaluation of GEOS-CHEM, a global three- dimensional (3-D) model of tropospheric chemistry driven by assimilated meteorological observations from the Goddard Earth Observing System (GEOS) of the NASA Data Assimilation Office (DAO). The model is applied to a 1-year simulation of tropospheric ozone-NO-hydrocarbon chemistry for 1994, and is evaluated with observations both for 1994 and for other years. It reproduces usually to within 10 ppb the concentrations of ozone observed from the worldwide ozonesonde data network. It simulates correctly the seasonal phases and amplitudes of ozone concentrations for different regions and altitudes, but tends to underestimate the seasonal amplitude at northern midlatitudes. Observed concentrations of NO and Peroxyacetylnitrate (PAN) observed in aircraft campaigns are generally reproduced to within a factor of 2 and often much better. Concentrations of HNO3 in the remote troposphere are overestimated typically by a factor of 2-3, a common problem in global models that may reflect a combination of insufficient precipitation scavenging and gas-aerosol partitioning not resolved by the model. The model yields an atmospheric lifetime of methylchloroform (proxy for global OH) of 5.1 years, as compared to a best estimate from observations of 5.5 +/- 0.8 years, and simulates H202 concentrations observed from aircraft with significant regional disagreements but no global bias. The OH concentrations are 20% higher than in our previous global 3-D model which included an UV-absorbing aerosol. Concentrations of CO tend to be underestimated by the model, often by 10-30 ppb, which could reflect a combination of excessive OH (a 20% decrease in model OH could be accommodated by the methylchloroform constraint) and an underestimate of CO sources (particularly biogenic). The model underestimates observed acetone concentrations over the South Pacific in fall by a factor of 3; a missing source from the ocean may be implicated.
Jennifer A Logan - One of the best experts on this subject based on the ideXlab platform.
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global modeling of tropospheric chemistry with assimilated meteorology model description and evaluation
Journal of Geophysical Research, 2001Co-Authors: Isabelle Bey, Daniel J Jacob, Jennifer A Logan, Arlene M Fiore, Robert M Yantosca, Brendan D Field, Honguy Y Liu, Loretta J Mickley, Martin G. SchultzAbstract:We present a first description and evaluation of GEOS-CHEM, a global three- dimensional (3-D) model of tropospheric chemistry driven by assimilated meteorological observations from the Goddard Earth Observing System (GEOS) of the NASA Data Assimilation Office (DAO). The model is applied to a 1-year simulation of tropospheric ozone-NO-hydrocarbon chemistry for 1994, and is evaluated with observations both for 1994 and for other years. It reproduces usually to within 10 ppb the concentrations of ozone observed from the worldwide ozonesonde data network. It simulates correctly the seasonal phases and amplitudes of ozone concentrations for different regions and altitudes, but tends to underestimate the seasonal amplitude at northern midlatitudes. Observed concentrations of NO and Peroxyacetylnitrate (PAN) observed in aircraft campaigns are generally reproduced to within a factor of 2 and often much better. Concentrations of HNO3 in the remote troposphere are overestimated typically by a factor of 2-3, a common problem in global models that may reflect a combination of insufficient precipitation scavenging and gas-aerosol partitioning not resolved by the model. The model yields an atmospheric lifetime of methylchloroform (proxy for global OH) of 5.1 years, as compared to a best estimate from observations of 5.5 +/- 0.8 years, and simulates H202 concentrations observed from aircraft with significant regional disagreements but no global bias. The OH concentrations are 20% higher than in our previous global 3-D model which included an UV-absorbing aerosol. Concentrations of CO tend to be underestimated by the model, often by 10-30 ppb, which could reflect a combination of excessive OH (a 20% decrease in model OH could be accommodated by the methylchloroform constraint) and an underestimate of CO sources (particularly biogenic). The model underestimates observed acetone concentrations over the South Pacific in fall by a factor of 3; a missing source from the ocean may be implicated.
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on the origin of tropospheric ozone and nox over the tropical south pacific
Journal of Geophysical Research, 1999Co-Authors: Martin G. Schultz, Daniel J Jacob, Jennifer A Logan, Yuhang Wang, Elliot L Atlas, D R Blake, N J Blake, J D Bradshaw, Edward V BrowellAbstract:The budgets of ozone and nitrogen oxides (NOx = NO + NO2) ill the tropical South Pacific troposphere are analyzed by photochemical point modeling of aircraft observations at 0-12 km altitude from the Pacific Exploratory Mission-Tropics A campaign flown in September- October 1996. The model reproduces the observed NO2/NO concentration ratio to within 30% and has similar success in simulating observed concentrations of peroxides (H202, CH3OOH), lending confidence in its use to investigate ozone chemistry. It is found that chemical production of ozone balances only half of chemical loss in the tropospheric column over the tropical South Pacific. The net loss is 1.8 x 1011 molecules cm -2 S '1. The missing source of ozone is matched by west- erly transport of continental pollution into the region. Independent analysis of the regional ozone budget with a global three-dimensional model corroborates the results from the point model and reveals the importance of biomass burning emissions in South America and Africa for the ozone budget over the tropical South Pacific. In this model, biomass burning increases average ozone concentrations by 7-8 ppbv throughout the troposphere. The NOx responsible for ozone produc- tion within the South Pacific troposphere below 4 km can be largely explained by decomposition of Peroxyacetylnitrate (PAN) transported into the region with biomass burning pollution at higher altitudes.
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global simulation of tropospheric o3 nox hydrocarbon chemistry 3 origin of tropospheric ozone and effects of nonmethane hydrocarbons
Journal of Geophysical Research, 1998Co-Authors: Yuhang Wang, Daniel J Jacob, Jennifer A LoganAbstract:A global three-dimensional model of tropospheric O3-NOx-hydrocarbon chemistry is used to investigate the factors controlling ozone concentrations in the troposphere. Model results indicate a close balance between chemical production and chemical loss of ozone in the tropospheric column at all latitudes (except high latitudes in winter). Using separate tracers for ozone produced in the stratosphere and in different regions of the troposphere, we find that the contribution of transport from the stratosphere to ozone concentrations in the troposphere is about 30% at midlatitudes in winter, 10% in summer, and 5% in the tropics. Production of ozone in the upper, middle, and continental lower troposphere all make significant contributions (10–50%) to ozone concentrations throughout the troposphere. The middle troposphere is a major global source region for ozone even though it is not a region of net production. The springtime maximum of ozone observed at remote sites in the northern extratropics is explained by a phase overlap between ozone transported from the stratosphere which peaks in late winter and ozone produced in the troposphere which peaks in late spring. Our model results do not support previous explanations of the springtime maximum based on wintertime accumulation of ozone or its precursors in the Arctic. The particularly strong springtime maximum at Mauna Loa Observatory (Hawaii) is attributed to long-range transport of Asian pollution over the North Pacific in spring. A sensitivity simulation without nonmethane hydrocarbons (NMHCs) indicates small decreases of ozone concentrations (<15%) in the remote troposphere and a 20% increase in the global mean OH concentration. Without NMHCs as a source of Peroxyacetylnitrate, concentrations of NOx decrease by 30% in the remote lower troposphere but increase by 70% in the continental lower troposphere and by 40% in the upper troposphere. Biogenic isoprene accounts for about half of the NMHC effects in the model.
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global simulation of tropospheric o3 nox hydrocarbon chemistry 2 model evaluation and global ozone budget
Journal of Geophysical Research, 1998Co-Authors: Yuhang Wang, Jennifer A Logan, Daniel J JacobAbstract:Results from a global three-dimensional model for tropospheric O3-NOx-hydrocarbon chemistry are presented and evaluated with surface, ozonesonde, and aircraft measurements. Seasonal variations and regional distributions of ozone, NO, Peroxyacetylnitrate (PAN), CO, ethane, acetone, and H2O2 are examined. The model reproduces observed NO and PAN concentrations to within a factor of 2 for a wide range of tropospheric regions including the upper troposphere but tends to overestimate HNO3 concentrations in the remote troposphere (sometimes several fold). This discrepancy implies a missing sink for HNO3 that does not lead to rapid recycling of NOx; only in the upper troposphere over the tropical South Atlantic would a fast conversion of HNO3 to NOx improve the model simulation for NOx. Observed concentrations of acetone are reproduced in the model by including a large biogenic source (15 Tg C yr−1), which accounts for 40% of the estimated global source of acetone (37 Tg C yr−1). Concentrations of H2O2 in various regions of the troposphere are simulated usually to within a factor of 2, providing a test for HOx chemistry in the model. The model reproduces well the observed concentrations and seasonal variations of ozone in the troposphere, with some exceptions including an underestimate of the vertical gradient across the tropical trade wind inversion. A global budget analysis in the model indicates that the supply and loss of tropospheric ozone are dominated by photochemistry within the troposphere and that NOx. emitted in the southern hemisphere is twice as efficient at producing ozone as NOx emitted in the northern hemisphere.
Yuhang Wang - One of the best experts on this subject based on the ideXlab platform.
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on the origin of tropospheric ozone and nox over the tropical south pacific
Journal of Geophysical Research, 1999Co-Authors: Martin G. Schultz, Daniel J Jacob, Jennifer A Logan, Yuhang Wang, Elliot L Atlas, D R Blake, N J Blake, J D Bradshaw, Edward V BrowellAbstract:The budgets of ozone and nitrogen oxides (NOx = NO + NO2) ill the tropical South Pacific troposphere are analyzed by photochemical point modeling of aircraft observations at 0-12 km altitude from the Pacific Exploratory Mission-Tropics A campaign flown in September- October 1996. The model reproduces the observed NO2/NO concentration ratio to within 30% and has similar success in simulating observed concentrations of peroxides (H202, CH3OOH), lending confidence in its use to investigate ozone chemistry. It is found that chemical production of ozone balances only half of chemical loss in the tropospheric column over the tropical South Pacific. The net loss is 1.8 x 1011 molecules cm -2 S '1. The missing source of ozone is matched by west- erly transport of continental pollution into the region. Independent analysis of the regional ozone budget with a global three-dimensional model corroborates the results from the point model and reveals the importance of biomass burning emissions in South America and Africa for the ozone budget over the tropical South Pacific. In this model, biomass burning increases average ozone concentrations by 7-8 ppbv throughout the troposphere. The NOx responsible for ozone produc- tion within the South Pacific troposphere below 4 km can be largely explained by decomposition of Peroxyacetylnitrate (PAN) transported into the region with biomass burning pollution at higher altitudes.
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global simulation of tropospheric o3 nox hydrocarbon chemistry 3 origin of tropospheric ozone and effects of nonmethane hydrocarbons
Journal of Geophysical Research, 1998Co-Authors: Yuhang Wang, Daniel J Jacob, Jennifer A LoganAbstract:A global three-dimensional model of tropospheric O3-NOx-hydrocarbon chemistry is used to investigate the factors controlling ozone concentrations in the troposphere. Model results indicate a close balance between chemical production and chemical loss of ozone in the tropospheric column at all latitudes (except high latitudes in winter). Using separate tracers for ozone produced in the stratosphere and in different regions of the troposphere, we find that the contribution of transport from the stratosphere to ozone concentrations in the troposphere is about 30% at midlatitudes in winter, 10% in summer, and 5% in the tropics. Production of ozone in the upper, middle, and continental lower troposphere all make significant contributions (10–50%) to ozone concentrations throughout the troposphere. The middle troposphere is a major global source region for ozone even though it is not a region of net production. The springtime maximum of ozone observed at remote sites in the northern extratropics is explained by a phase overlap between ozone transported from the stratosphere which peaks in late winter and ozone produced in the troposphere which peaks in late spring. Our model results do not support previous explanations of the springtime maximum based on wintertime accumulation of ozone or its precursors in the Arctic. The particularly strong springtime maximum at Mauna Loa Observatory (Hawaii) is attributed to long-range transport of Asian pollution over the North Pacific in spring. A sensitivity simulation without nonmethane hydrocarbons (NMHCs) indicates small decreases of ozone concentrations (<15%) in the remote troposphere and a 20% increase in the global mean OH concentration. Without NMHCs as a source of Peroxyacetylnitrate, concentrations of NOx decrease by 30% in the remote lower troposphere but increase by 70% in the continental lower troposphere and by 40% in the upper troposphere. Biogenic isoprene accounts for about half of the NMHC effects in the model.
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global simulation of tropospheric o3 nox hydrocarbon chemistry 2 model evaluation and global ozone budget
Journal of Geophysical Research, 1998Co-Authors: Yuhang Wang, Jennifer A Logan, Daniel J JacobAbstract:Results from a global three-dimensional model for tropospheric O3-NOx-hydrocarbon chemistry are presented and evaluated with surface, ozonesonde, and aircraft measurements. Seasonal variations and regional distributions of ozone, NO, Peroxyacetylnitrate (PAN), CO, ethane, acetone, and H2O2 are examined. The model reproduces observed NO and PAN concentrations to within a factor of 2 for a wide range of tropospheric regions including the upper troposphere but tends to overestimate HNO3 concentrations in the remote troposphere (sometimes several fold). This discrepancy implies a missing sink for HNO3 that does not lead to rapid recycling of NOx; only in the upper troposphere over the tropical South Atlantic would a fast conversion of HNO3 to NOx improve the model simulation for NOx. Observed concentrations of acetone are reproduced in the model by including a large biogenic source (15 Tg C yr−1), which accounts for 40% of the estimated global source of acetone (37 Tg C yr−1). Concentrations of H2O2 in various regions of the troposphere are simulated usually to within a factor of 2, providing a test for HOx chemistry in the model. The model reproduces well the observed concentrations and seasonal variations of ozone in the troposphere, with some exceptions including an underestimate of the vertical gradient across the tropical trade wind inversion. A global budget analysis in the model indicates that the supply and loss of tropospheric ozone are dominated by photochemistry within the troposphere and that NOx. emitted in the southern hemisphere is twice as efficient at producing ozone as NOx emitted in the northern hemisphere.
Martin G. Schultz - One of the best experts on this subject based on the ideXlab platform.
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A global simulation of tropospheric ozone and related tracers: Description and evaluation of MOZART, version 2
Journal of Geophysical Research: Atmospheres, 2003Co-Authors: Larry W Horowitz, Xuexi Tie, Stacy Walters, Claire Granier, Martin G. Schultz, Louisa K. Emmons, Denise L Mauzerall, Philip J Rasch, Jean-francois Lamarque, Geoffrey S TyndallAbstract:We have developed a global three-dimensional chemical transport model called Model of Ozone and Related Chemical Tracers (MOZART), version 2. This model, which will be made available to the community, is built on the framework of the National Center for Atmospheric Research (NCAR) Model of Atmospheric Transport and Chemistry (MATCH) and can easily be driven with various meteorological inputs and model resolutions. In this work, we describe the standard configuration of the model, in which the model is driven by meteorological inputs every 3 hours from the middle atmosphere version of the NCAR Community Climate Model (MACCM3) and uses a 20-min time step and a horizontal resolution of 2.8° latitude × 2.8° longitude with 34 vertical levels extending up to approximately 40 km. The model includes a detailed chemistry scheme for tropospheric ozone, nitrogen oxides, and hydrocarbon chemistry, with 63 chemical species. Tracer advection is performed using a flux-form semi-Lagrangian scheme with a pressure fixer. Subgrid-scale convective and boundary layer parameterizations are included in the model. Surface emissions include sources from fossil fuel combustion, biofuel and biomass burning, biogenic and soil emissions, and oceanic emissions. Parameterizations of dry and wet deposition are included. Stratospheric concentrations of several long-lived species (including ozone) are constrained by relaxation toward climatological values. The distribution of tropospheric ozone is well simulated in the model, including seasonality and horizontal and vertical gradients. However, the model tends to overestimate ozone near the tropopause at high northern latitudes. Concentrations of nitrogen oxides (NOx) and nitric acid (HNO3) agree well with observed values, but Peroxyacetylnitrate (PAN) is overestimated by the model in the upper troposphere at several locations. Carbon monoxide (CO) is simulated well at most locations, but the seasonal cycle is underestimated at some sites in the Northern Hemisphere. We find that in situ photochemical production and loss dominate the tropospheric ozone budget, over input from the stratosphere and dry deposition. Approximately 75% of the tropospheric production and loss of ozone occurs within the tropics, with large net production in the tropical upper troposphere. Tropospheric production and loss of ozone are three to four times greater in the northern extratropics than the southern extratropics. The global sources of CO consist of photochemical production (55%) and direct emissions (45%). The tropics dominate the chemistry of CO, accounting for about 75% of the tropospheric production and loss. The global budgets of tropospheric ozone and CO are generally consistent with the range found in recent studies. The lifetime of methane (9.5 years) and methylchloroform (5.7 years) versus oxidation by tropospheric hydroxyl radical (OH), two useful measures of the global abundance of OH, agree well with recent estimates. Concentrations of nonmethane hydrocarbons and oxygenated intermediates (carbonyls and peroxides) generally agree well with observations.
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global modeling of tropospheric chemistry with assimilated meteorology model description and evaluation
Journal of Geophysical Research, 2001Co-Authors: Isabelle Bey, Daniel J Jacob, Jennifer A Logan, Arlene M Fiore, Robert M Yantosca, Brendan D Field, Honguy Y Liu, Loretta J Mickley, Martin G. SchultzAbstract:We present a first description and evaluation of GEOS-CHEM, a global three- dimensional (3-D) model of tropospheric chemistry driven by assimilated meteorological observations from the Goddard Earth Observing System (GEOS) of the NASA Data Assimilation Office (DAO). The model is applied to a 1-year simulation of tropospheric ozone-NO-hydrocarbon chemistry for 1994, and is evaluated with observations both for 1994 and for other years. It reproduces usually to within 10 ppb the concentrations of ozone observed from the worldwide ozonesonde data network. It simulates correctly the seasonal phases and amplitudes of ozone concentrations for different regions and altitudes, but tends to underestimate the seasonal amplitude at northern midlatitudes. Observed concentrations of NO and Peroxyacetylnitrate (PAN) observed in aircraft campaigns are generally reproduced to within a factor of 2 and often much better. Concentrations of HNO3 in the remote troposphere are overestimated typically by a factor of 2-3, a common problem in global models that may reflect a combination of insufficient precipitation scavenging and gas-aerosol partitioning not resolved by the model. The model yields an atmospheric lifetime of methylchloroform (proxy for global OH) of 5.1 years, as compared to a best estimate from observations of 5.5 +/- 0.8 years, and simulates H202 concentrations observed from aircraft with significant regional disagreements but no global bias. The OH concentrations are 20% higher than in our previous global 3-D model which included an UV-absorbing aerosol. Concentrations of CO tend to be underestimated by the model, often by 10-30 ppb, which could reflect a combination of excessive OH (a 20% decrease in model OH could be accommodated by the methylchloroform constraint) and an underestimate of CO sources (particularly biogenic). The model underestimates observed acetone concentrations over the South Pacific in fall by a factor of 3; a missing source from the ocean may be implicated.
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on the origin of tropospheric ozone and nox over the tropical south pacific
Journal of Geophysical Research, 1999Co-Authors: Martin G. Schultz, Daniel J Jacob, Jennifer A Logan, Yuhang Wang, Elliot L Atlas, D R Blake, N J Blake, J D Bradshaw, Edward V BrowellAbstract:The budgets of ozone and nitrogen oxides (NOx = NO + NO2) ill the tropical South Pacific troposphere are analyzed by photochemical point modeling of aircraft observations at 0-12 km altitude from the Pacific Exploratory Mission-Tropics A campaign flown in September- October 1996. The model reproduces the observed NO2/NO concentration ratio to within 30% and has similar success in simulating observed concentrations of peroxides (H202, CH3OOH), lending confidence in its use to investigate ozone chemistry. It is found that chemical production of ozone balances only half of chemical loss in the tropospheric column over the tropical South Pacific. The net loss is 1.8 x 1011 molecules cm -2 S '1. The missing source of ozone is matched by west- erly transport of continental pollution into the region. Independent analysis of the regional ozone budget with a global three-dimensional model corroborates the results from the point model and reveals the importance of biomass burning emissions in South America and Africa for the ozone budget over the tropical South Pacific. In this model, biomass burning increases average ozone concentrations by 7-8 ppbv throughout the troposphere. The NOx responsible for ozone produc- tion within the South Pacific troposphere below 4 km can be largely explained by decomposition of Peroxyacetylnitrate (PAN) transported into the region with biomass burning pollution at higher altitudes.
Melody A Avery - One of the best experts on this subject based on the ideXlab platform.
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transpacific transport of ozone pollution and the effect of recent asian emission increases on air quality in north america an integrated analysis using satellite aircraft ozonesonde and surface observations
Atmospheric Chemistry and Physics, 2008Co-Authors: Lin Zhang, Daniel J Jacob, Daniel A. Jaffe, Anne M. Thompson, K F Boersma, J R Olson, Kevin W Bowman, J Worden, Melody A AveryAbstract:We use an ensemble of aircraft, satellite, sonde, and surface observations for April–May 2006 (NASA/INTEX-B aircraft campaign) to better understand the mechanisms for transpacific ozone pollution and its implications for North American air quality. The observations are interpreted with a global 3-D chemical transport model (GEOS-Chem). OMI NO 2 satellite observations constrain Asian anthropogenic NO x emissions and indicate a factor of 2 increase from 2000 to 2006 in China. Satellite observations of CO from AIRS and TES indicate two major events of Asian transpacific pollution during INTEX-B. Correlation between TES CO and ozone observations shows evidence for transpacific ozone pollution. The semi-permanent Pacific High and Aleutian Low cause splitting of transpacific pollution plumes over the Northeast Pacific. The northern branch circulates around the Aleutian Low and has little impact on North America. The southern branch circulates around the Pacific High and some of that air impacts western North America. Both aircraft measurements and model results show sustained ozone production driven by Peroxyacetylnitrate (PAN) decomposition in the southern branch, roughly doubling the transpacific influence from ozone produced in the Asian boundary layer. Model simulation of ozone observations at Mt. Bachelor Observatory in Oregon (2.7 km altitude) indicates a mean Asian ozone pollution contribution of 9±3 ppbv to the mean observed concentration of 54 ppbv, reflecting mostly an enhancement in background ozone rather than episodic Asian plumes. Asian pollution enhanced surface ozone concentrations by 5–7 ppbv over western North America in spring 2006. The 2000–2006 rise in Asian anthropogenic emissions increased this influence by 1–2 ppbv.