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Articles 31 - 60 of 155

Full-Text Articles in Physical Sciences and Mathematics

Modeling Chemistry In And Above Snow At Summit, Greenland – Part 1: Model Description And Results, J L. Thomas, J Stutz, Barry Lefer, L Gregory Huey, K Toyota, Jack E. Dibb, R Von Glasow May 2011

Modeling Chemistry In And Above Snow At Summit, Greenland – Part 1: Model Description And Results, J L. Thomas, J Stutz, Barry Lefer, L Gregory Huey, K Toyota, Jack E. Dibb, R Von Glasow

Earth Sciences

Sun-lit snow is increasingly recognized as a chemical reactor that plays an active role in uptake, transformation, and release of atmospheric trace gases. Snow is known to influence boundary layer air on a local scale, and given the large global surface coverage of snow may also be significant on regional and global scales. We present a new detailed one-dimensional snow chemistry module that has been coupled to the 1-D atmospheric boundary layer model MISTRA. The new 1-D snow module, which is dynamically coupled to the overlaying atmospheric model, includes heat transport in the snowpack, molecular diffusion, and wind pumping of …

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Multi-Scale Modeling Study Of The Source Contributions To Near-Surface Ozone And Sulfur Oxides Levels Over California During The Arctas-Carb Period, M. Huang, Gregory R. Carmichael, S N. Spak, B Adhikary, S Kulkarni, Y Cheng, C Wei, Y Tang, A D'Allura, Paul Wennberg, L Gregory Huey, Jack E. Dibb, Jose L. Jimenez, Michael J. Cubison, Andrew Weinheimer, Ajith P. Kaduwela, Chenxia Cai, M Wong, R Bradley Pierce, J Al-Saadi, David G. Streets, Q Zhang Apr 2011

Multi-Scale Modeling Study Of The Source Contributions To Near-Surface Ozone And Sulfur Oxides Levels Over California During The Arctas-Carb Period, M. Huang, Gregory R. Carmichael, S N. Spak, B Adhikary, S Kulkarni, Y Cheng, C Wei, Y Tang, A D'Allura, Paul Wennberg, L Gregory Huey, Jack E. Dibb, Jose L. Jimenez, Michael J. Cubison, Andrew Weinheimer, Ajith P. Kaduwela, Chenxia Cai, M Wong, R Bradley Pierce, J Al-Saadi, David G. Streets, Q Zhang

Earth Sciences

Chronic high surface ozone (O3) levels and the increasing sulfur oxides (SOx = SO2+SO4) ambient concentrations over South Coast (SC) and other areas of California (CA) are affected by both local emissions and long-range transport. In this paper, multi-scale tracer, full-chemistry and adjoint simulations using the STEM atmospheric chemistry model are conducted to assess the contribution of local emission sourcesto SC O3 and to evaluate the impacts of transported sulfur and local emissions on the SC sulfur budgetduring the ARCTAS-CARB experiment period in 2008. Sensitivity simulations quantify contributions of biogenic and fire …

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A New Interpretation Of Total Column Bro During Arctic Spring, R J. Salawitch, T Canty, T P. Kurosu, K Chance, Q Liang, Arlindo Da Silva, S Pawson, J E. Neilsen, J. V. Rodriguez, P K. Bhartia, X Liu, L Gregory Huey, J Liao, R E. Stickel, D Tanner, Jack E. Dibb, W R. Simpson, D Donohue, Andrew Weinheimer, F Flocke, D Knapp, D Montzka, J A. Neuman, J Nowak, Thomas B. Ryerson, S J. Oltmans, D R. Blake, E L. Atlas, D Kinnison, S Tilmes, L L. Pan, F Hendrick, R Bradley Pierce, M Van Roozendael, K Kreher, P V. Johnston, R S. Gao, B Johnson, T P. Bui, G Chen, R B. Pierce, J H. Crawford, D J. Jacob Nov 2010

A New Interpretation Of Total Column Bro During Arctic Spring, R J. Salawitch, T Canty, T P. Kurosu, K Chance, Q Liang, Arlindo Da Silva, S Pawson, J E. Neilsen, J. V. Rodriguez, P K. Bhartia, X Liu, L Gregory Huey, J Liao, R E. Stickel, D Tanner, Jack E. Dibb, W R. Simpson, D Donohue, Andrew Weinheimer, F Flocke, D Knapp, D Montzka, J A. Neuman, J Nowak, Thomas B. Ryerson, S J. Oltmans, D R. Blake, E L. Atlas, D Kinnison, S Tilmes, L L. Pan, F Hendrick, R Bradley Pierce, M Van Roozendael, K Kreher, P V. Johnston, R S. Gao, B Johnson, T P. Bui, G Chen, R B. Pierce, J H. Crawford, D J. Jacob

Earth Sciences

Emission of bromine from sea-salt aerosol, frost flowers, ice leads, and snow results in the nearly complete removal of surface ozone during Arctic spring. Regions of enhanced total column BrO observed by satellites have traditionally been associated with these emissions. However, airborne measurements of BrO and O3 within the convective boundary layer (CBL) during the ARCTAS and ARCPAC field campaigns at times bear little relation to enhanced column BrO. We show that the locations of numerous satellite BrO “hotspots” during Arctic spring are consistent with observations of total column ozone and tropopause height, suggesting a stratospheric origin to these …

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Bromide And Other Ions In The Snow, Firn Air, And Atmospheric Boundary Layer At Summit During Gshox, Jack E. Dibb, Luke D. Ziemba, J Luxford, P Beckman Oct 2010

Bromide And Other Ions In The Snow, Firn Air, And Atmospheric Boundary Layer At Summit During Gshox, Jack E. Dibb, Luke D. Ziemba, J Luxford, P Beckman

Earth Sciences

Measurements of gas phase soluble bromide in the boundary layer and in firn air, and Br− in aerosol and snow, were made at Summit, Greenland (72.5° N, 38.4° W, 3200 m a.s.l.) as part of a larger investigation into the influence of Br chemistry on HOx cycling. The soluble bromide measurements confirm that photochemical activation of Br− in the snow causes release of active Br to the overlying air despite trace concentrations of Br− in the snow (means 15 and 8 nmol Br− kg−1 of snow in 2007 and 2008, respectively). Mixing ratios of …

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The Production And Persistence Of Σrono2 In The Mexico City Plume, A E. Perring, T H. Bertram, D K. Farmer, Paul J. Wooldridge, Jack E. Dibb, N J. Blake, D R. Blake, H B. Singh, H Fuelberg, Glenn Diskin, G W. Sachse, Robert C. Cohen Aug 2010

The Production And Persistence Of Σrono2 In The Mexico City Plume, A E. Perring, T H. Bertram, D K. Farmer, Paul J. Wooldridge, Jack E. Dibb, N J. Blake, D R. Blake, H B. Singh, H Fuelberg, Glenn Diskin, G W. Sachse, Robert C. Cohen

Earth Sciences

Alkyl and multifunctional nitrates (RONO2, ΣANs) have been observed to be a significant fraction of NOy in a number of different chemical regimes. Their formation is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. ΣANs also represent a potentially large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Numerous studies have investigated the role of nitrate formation from biogenic compounds and in the remote atmosphere. Less attention has been paid to the role ΣANs may …

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Synthesis Of Satellite (Modis), Aircraft (Icartt), And Surface (Improve, Epa-Aqs, Aeronet) Aerosol Observations Over Eastern North America To Improve Modis Aerosol Retrievals And Constrain Surface Aerosol Concentrations And Sources, Easan Drury, Daniel J. Jacob, Robert J.D. Spurr, Jun Wang, Yohei Shinozuka, Bruce E. Anderson, A D. Clarke, Jack E. Dibb, Cameron Mcnaughton, Rodney J. Weber Jul 2010

Synthesis Of Satellite (Modis), Aircraft (Icartt), And Surface (Improve, Epa-Aqs, Aeronet) Aerosol Observations Over Eastern North America To Improve Modis Aerosol Retrievals And Constrain Surface Aerosol Concentrations And Sources, Easan Drury, Daniel J. Jacob, Robert J.D. Spurr, Jun Wang, Yohei Shinozuka, Bruce E. Anderson, A D. Clarke, Jack E. Dibb, Cameron Mcnaughton, Rodney J. Weber

Earth Sciences

We use an ensemble of satellite (MODIS), aircraft, and ground-based aerosol observations during the ICARTT field campaign over eastern North America in summer 2004 to (1) examine the consistency between different aerosol measurements, (2) evaluate a new retrieval of aerosol optical depths (AODs) and inferred surface aerosol concentrations (PM2.5) from the MODIS satellite instrument, and (3) apply this collective information to improve our understanding of aerosol sources. The GEOS-Chem global chemical transport model (CTM) provides a transfer platform between the different data sets, allowing us to evaluate the consistency between different aerosol parameters observed at different times and …

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The Arctic Research Of The Composition Of The Troposphere From Aircraft And Satellites (Arctas) Mission: Design, Execution, And First Results, D J. Jacob, J H. Crawford, H Maring, A D. Clarke, Jack E. Dibb, L K. Emmons, R A. Ferrare, C A. Hostetler, Phil Russell, H B. Singh, A M. Thompson, G E. Shaw, E Mccauley, Judith Pederson, Jenny Fisher Jun 2010

The Arctic Research Of The Composition Of The Troposphere From Aircraft And Satellites (Arctas) Mission: Design, Execution, And First Results, D J. Jacob, J H. Crawford, H Maring, A D. Clarke, Jack E. Dibb, L K. Emmons, R A. Ferrare, C A. Hostetler, Phil Russell, H B. Singh, A M. Thompson, G E. Shaw, E Mccauley, Judith Pederson, Jenny Fisher

Earth Sciences

The NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission was conducted in two 3-week deployments based in Alaska (April 2008) and western Canada (June–July 2008). Its goal was to better understand the factors driving current changes in Arctic atmospheric composition and climate, including (1) influx of mid-latitude pollution, (2) boreal forest fires, (3) aerosol radiative forcing, and (4) chemical processes. The June–July deployment was preceded by one week of flights over California (ARCTAS-CARB) focused on (1) improving state emission inventories for greenhouse gases and aerosols, (2) providing observations to test and improve models …

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Convective Distribution Of Tropospheric Ozone And Tracers In The Central American Itcz Region: Evidence From Observations During Tc4, M A. Avery, Cynthia Twohy, David Mccabe, J Joiner, Kurt Severance, E L. Atlas, D R. Blake, T P. Bui, John D. Crounse, Jack E. Dibb, Glenn Diskin, Paul Lawson, Matthew Mcgill, David Rogers, G W. Sachse, Eric Scheuer, A M. Thompson, Charles Trepte, Paul Wennberg, Jerald Ziemke May 2010

Convective Distribution Of Tropospheric Ozone And Tracers In The Central American Itcz Region: Evidence From Observations During Tc4, M A. Avery, Cynthia Twohy, David Mccabe, J Joiner, Kurt Severance, E L. Atlas, D R. Blake, T P. Bui, John D. Crounse, Jack E. Dibb, Glenn Diskin, Paul Lawson, Matthew Mcgill, David Rogers, G W. Sachse, Eric Scheuer, A M. Thompson, Charles Trepte, Paul Wennberg, Jerald Ziemke

Earth Sciences

During the Tropical Composition, Clouds and Climate Coupling (TC4) experiment that occurred in July and August of 2007, extensive sampling of active convection in the ITCZ region near Central America was performed from multiple aircraft and satellite sensors. As part of a sampling strategy designed to study cloud processes, the NASA ER‐2, WB‐57 and DC‐8 flew in stacked “racetrack patterns” in convective cells. On July 24, 2007, the ER‐2 and DC‐8 probed an actively developing storm and the DC‐8 was hit by lightning. Case studies of this flight, and of convective outflow on August 5, 2007 reveal a significant anti‐correlation …

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Evidence Of Nitric Acid Uptake In Warm Cirrus Anvil Clouds During The Nasa Tc4 Campaign, Eric Scheuer, Jack E. Dibb, Cynthia Twohy, David Rogers, Andrew J. Heymsfield, Aaron Bansemer May 2010

Evidence Of Nitric Acid Uptake In Warm Cirrus Anvil Clouds During The Nasa Tc4 Campaign, Eric Scheuer, Jack E. Dibb, Cynthia Twohy, David Rogers, Andrew J. Heymsfield, Aaron Bansemer

Earth Sciences

Uptake of HNO3 onto cirrus ice may play an important role in tropospheric NOx cycling. Discrepancies between modeled and in situ measurements of gas-phase HNO3 in the troposphere suggest that redistribution and removal mechanisms by cirrus ice have been poorly constrained. Limited in situ measurements have provided somewhat differing results and are not fully compatible with theory developed from laboratory studies. We present new airborne measurements of HNO3 in cirrus clouds from anvil outflow made during the Tropical Composition, Cloud, and Climate Coupling Experiment (TC4). Upper tropospheric (>9 km) measurements made during three flights while repeatedly traversing the same …

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Impact Of Mineral Dust On Nitrate, Sulfate, And Ozone In Transpacific Asian Pollution Plumes, T D. Fairlie, D J. Jacob, Jack E. Dibb, B Alexander, M A. Avery, Aaron Van Donkelaar, L Zhang Apr 2010

Impact Of Mineral Dust On Nitrate, Sulfate, And Ozone In Transpacific Asian Pollution Plumes, T D. Fairlie, D J. Jacob, Jack E. Dibb, B Alexander, M A. Avery, Aaron Van Donkelaar, L Zhang

Earth Sciences

We use a 3-D global chemical transport model (GEOS-Chem) to interpret aircraft observations of nitrate and sulfate partitioning in transpacific dust plumes during the INTEX-B campaign of April–May 2006. The model includes explicit transport of size-resolved mineral dust and its alkalinity, nitrate, and sulfate content. The observations show that particulate nitrate is primarily associated with dust, sulfate is primarily associated with ammonium, and Asian dust remains alkaline across the Pacific. This can be reproduced in the model by using a reactive uptake coefficient for HNO3 on dust (γ(HNO3) ~10−3) much lower than commonly assumed in …

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A Regional Scale Modeling Analysis Of Aerosol And Trace Gas Distributions Over The Eastern Pacific During The Intex-B Field Campaign, B Adhikary, Gregory R. Carmichael, S Kulkarni, C Wei, Y Tang, A D'Allura, M Mena-Carrasco, David G. Streets, Q Zhang, R B. Pierce, J Al-Saadi, L K. Emmons, G G. Pfister, M A. Avery, J D. Barrick, D R. Blake, William H. Brune, Robert C. Cohen, Jack E. Dibb, A Fried, B J. Heikes, L Gregory Huey, D W. O'Sullivan, G W. Sachse, R E. Shetter, H B. Singh, T L. Campos, C A. Cantrell, F Flocke, E J. Dunlea, Jose L. Jimenez, Andrew Weinheimer, John D. Crounse, Paul Wennberg, James J. Schauer, E A. Stone, D A. Jaffe, D R. Reidmiller Mar 2010

A Regional Scale Modeling Analysis Of Aerosol And Trace Gas Distributions Over The Eastern Pacific During The Intex-B Field Campaign, B Adhikary, Gregory R. Carmichael, S Kulkarni, C Wei, Y Tang, A D'Allura, M Mena-Carrasco, David G. Streets, Q Zhang, R B. Pierce, J Al-Saadi, L K. Emmons, G G. Pfister, M A. Avery, J D. Barrick, D R. Blake, William H. Brune, Robert C. Cohen, Jack E. Dibb, A Fried, B J. Heikes, L Gregory Huey, D W. O'Sullivan, G W. Sachse, R E. Shetter, H B. Singh, T L. Campos, C A. Cantrell, F Flocke, E J. Dunlea, Jose L. Jimenez, Andrew Weinheimer, John D. Crounse, Paul Wennberg, James J. Schauer, E A. Stone, D A. Jaffe, D R. Reidmiller

Earth Sciences

The Sulfur Transport and dEposition Model (STEM) is applied to the analysis of observations obtained during the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B), conducted over the eastern Pacific Ocean during spring 2006. Predicted trace gas and aerosol distributions over the Pacific are presented and discussed in terms of transport and source region contributions. Trace species distributions show a strong west (high) to east (low) gradient, with the bulk of the pollutant transport over the central Pacific occurring between ∼20° N and 50° N in the 2-6 km altitude range. These distributions are evaluated in the eastern Pacific by comparison with …

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Observations Of Heterogeneous Reactions Between Asian Pollution And Mineral Dust Over The Eastern North Pacific During Intex-B, Cameron Mcnaughton, A D. Clarke, V Kapustin, Yohei Shinozuka, S G. Howell, B E. Anderson, E L. Winstead, Jack E. Dibb, Eric Scheuer, Ronald C. Cohen, Paul J. Wooldridge, A E. Perring, L Gregory Huey, S Kim, Jose L. Jimenez, E J. Dunlea, P F. Decarlo, Paul Wennberg, John D. Crounse, Andrew Weinheimer, F Flocke Nov 2009

Observations Of Heterogeneous Reactions Between Asian Pollution And Mineral Dust Over The Eastern North Pacific During Intex-B, Cameron Mcnaughton, A D. Clarke, V Kapustin, Yohei Shinozuka, S G. Howell, B E. Anderson, E L. Winstead, Jack E. Dibb, Eric Scheuer, Ronald C. Cohen, Paul J. Wooldridge, A E. Perring, L Gregory Huey, S Kim, Jose L. Jimenez, E J. Dunlea, P F. Decarlo, Paul Wennberg, John D. Crounse, Andrew Weinheimer, F Flocke

Earth Sciences

In-situ airborne measurements of trace gases, aerosol size distributions, chemistry and optical properties were conducted over Mexico and the Eastern North Pacific during MILAGRO and INTEX-B. Heterogeneous reactions between secondary aerosol precursor gases and mineral dust lead to sequestration of sulfur, nitrogen and chlorine in the supermicrometer particulate size range.

Simultaneous measurements of aerosol size distributions and weak-acid soluble calcium result in an estimate of 11 wt% of CaCO3 for Asian dust. During transport across the North Pacific, ∼5ĝ€ "30% of the CaCO3 is converted to CaSO4 or Ca(NO 3)2 with an additional ∼4% consumed through reactions with HCl. The …

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Airborne Observations Of Total Rono2: New Constraints On The Yield And Lifetime Of Isoprene Nitrates, A E. Perring, T H. Bertram, Paul J. Wooldridge, A Fried, B J. Heikes, Jack E. Dibb, John D. Crounse, Paul Wennberg, N J. Blake, D R. Blake, William H. Brune, H B. Singh, Robert C. Cohen Feb 2009

Airborne Observations Of Total Rono2: New Constraints On The Yield And Lifetime Of Isoprene Nitrates, A E. Perring, T H. Bertram, Paul J. Wooldridge, A Fried, B J. Heikes, Jack E. Dibb, John D. Crounse, Paul Wennberg, N J. Blake, D R. Blake, William H. Brune, H B. Singh, Robert C. Cohen

Earth Sciences

Formation of isoprene nitrates (INs) is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. Isoprene nitrates also represent a potentially large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Current assessments indicate that formation rates of isoprene nitrates are uncertain to a factor of 2ĝ€"3 and the subsequent fate of isoprene nitrates remains largely unconstrained by laboratory, field or modeling studies. Measurements of total alkyl and multifunctional nitrates (ΣANs), NO2, total peroxy nitrates (ΣPNs), HNO3, CH2O, isoprene and …

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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, D Zhang, D J. Jacob, K F. Boersma, D A. Jaffe, J R. Olson, K W. Bowman, J Worden, A M. Thompson, M A. Avery, Ronald C. Cohen, Jack E. Dibb, F Flocke, H Fuelberg, L Gregory Huey, W W. Mcmillan, H B. Singh, Andrew Weinheimer Oct 2008

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, D Zhang, D J. Jacob, K F. Boersma, D A. Jaffe, J R. Olson, K W. Bowman, J Worden, A M. Thompson, M A. Avery, Ronald C. Cohen, Jack E. Dibb, F Flocke, H Fuelberg, L Gregory Huey, W W. Mcmillan, H B. Singh, Andrew Weinheimer

Earth Sciences

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 NO2 satellite observations constrain Asian anthropogenic NOx 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 …

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Enhanced Secondary Organic Aerosol Formation Due To Water Uptake By Fine Particles, Stephen R. Hennigan, M Bergin, Jack E. Dibb, Rodney J. Weber Sep 2008

Enhanced Secondary Organic Aerosol Formation Due To Water Uptake By Fine Particles, Stephen R. Hennigan, M Bergin, Jack E. Dibb, Rodney J. Weber

Earth Sciences

This study characterizes the partitioning behavior of a significant fraction of the ambient organic aerosol through simultaneous measurements of gas and particle watersoluble organic carbon (WSOC). During the summer in Atlanta, WSOC gas/particle partitioning showed a strong RH dependence that was attributed to particulate liquid water. At elevated RH levels (>70%) a significant increase in WSOC partitioning to the particle phase was observed and followed the predicted water uptake by fine particles. The enhancement in particle-phase partitioning translated to increased median particle WSOC concentrations ranging from 0.3 –0.9 mgCm3 . The results provide a detailed overview of the WSOC …

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Simultaneous Measurements Of Particulate And Gas-Phase Water-Soluble Organic Carbon Concentrations At Remote And Urban-Influenced Locations, C Anderson, Jack E. Dibb, Robert J. Griffin, M Bergin Jul 2008

Simultaneous Measurements Of Particulate And Gas-Phase Water-Soluble Organic Carbon Concentrations At Remote And Urban-Influenced Locations, C Anderson, Jack E. Dibb, Robert J. Griffin, M Bergin

Earth Sciences

The sources, sinks, and overall importance of watersoluble organic carbon (WSOC) in the atmosphere are not well understood. Although the primary historical focus has been on particulate WSOC (WSOCP), here we also present results obtained using a newly developed technique that additionally measures gas-phase water-soluble organic carbon (WSOCG). These first-of-their-kind measurements show that WSOCG can often be more than ten times larger than WSOCP at both urban and remote locations. The average fraction of WSOC residing in the gas phase (fg = WSOCG/(WSOCG + WSOCP)) at five various field sites ranged from 0.64 to 0.93, implying significant differences in WSOC …

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Analysis Of Aircraft And Satellite Measurements From The Intercontinental Chemical Transport Experiment (Intex-B) To Quantify Long-Range Transport Of East Asian Sulfur To Canada, Aaron Van Donkelaar, R V. Martin, W R. Leaitch, A M. Macdonald, T W. Walker, David G. Streets, Q Zhang, E J. Dunlea, Jose L. Jimenez, Jack E. Dibb, L Gregory Huey, Rodney J. Weber, M O. Andreae Jun 2008

Analysis Of Aircraft And Satellite Measurements From The Intercontinental Chemical Transport Experiment (Intex-B) To Quantify Long-Range Transport Of East Asian Sulfur To Canada, Aaron Van Donkelaar, R V. Martin, W R. Leaitch, A M. Macdonald, T W. Walker, David G. Streets, Q Zhang, E J. Dunlea, Jose L. Jimenez, Jack E. Dibb, L Gregory Huey, Rodney J. Weber, M O. Andreae

Earth Sciences

We interpret a suite of satellite, aircraft, and ground-based measurements over the North Pacific Ocean and western North America during April–May 2006 as part of the Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign to understand the implications of long-range transport of East Asian emissions to North America. The Canadian component of INTEX-B included 33 vertical profiles from a Cessna 207 aircraft equipped with an aerosol mass spectrometer. Long-range transport of organic aerosols was insignificant, contrary to expectations. Measured sulfate plumes in the free troposphere over British Columbia exceeded 2 μg/m3. We update the global anthropogenic emission inventory in a …

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Local Anthropogenic Impact On Particulate Elemental Carbon Concentrations At Summit, Greenland, Gayle S.W. Hagler, M Bergin, E A. Smith, M Town, Jack E. Dibb May 2008

Local Anthropogenic Impact On Particulate Elemental Carbon Concentrations At Summit, Greenland, Gayle S.W. Hagler, M Bergin, E A. Smith, M Town, Jack E. Dibb

Earth Sciences

Summit, Greenland is a remote Arctic research station allowing for field measurements at the highest point of the Greenland Ice Sheet. Due to the current reliance on diesel generators for electricity at Summit, unavoidable local emissions are a potential contamination threat to the measurement of combustion-related species in the air and snow. The effect of fossil-fuel combustion on particulate elemental carbon (EC) is assessed by a combination of ambient measurements (∼1 km from the main camp), a series of snow pits, and Gaussian plume modeling. Ambient measurements indicate that the air directly downwind of the research station generators experiences particulate …

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The Impact Of Local Sources And Long-Range Transport On Aerosol Properties Over The Northeast U.S. Region During Intex-Na, K L. Thornhill, Gao Chen, Jack E. Dibb, C. Jordan, Ali Omar, E L. Winstead, Greg Schuster, A D. Clarke, Cameron Mcnaughton, Eric Scheuer, D R. Blake, Glen Sachse, L Gregory Huey, H B. Singh, Bruce E. Anderson Apr 2008

The Impact Of Local Sources And Long-Range Transport On Aerosol Properties Over The Northeast U.S. Region During Intex-Na, K L. Thornhill, Gao Chen, Jack E. Dibb, C. Jordan, Ali Omar, E L. Winstead, Greg Schuster, A D. Clarke, Cameron Mcnaughton, Eric Scheuer, D R. Blake, Glen Sachse, L Gregory Huey, H B. Singh, Bruce E. Anderson

Earth Sciences

We use data collected aboard the NASA DC-8 aircraft during the summer 2004, Intercontinental Transport and Chemical Evolution Experiment over North America (INTEX-NA) field campaign to examine the origin, composition, physical and optical properties of aerosols within air masses sampled over and downwind of the northeastern U.S. We note that aerosol concentrations within the region exhibited steep vertical gradients and significant variability in both time and space. An examination of air mass chemical signatures and backward trajectories indicates that transport from four, significantly different source regions contributed to the variability: the subtropical Atlantic Ocean (AO); the U.S. west coast and …

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Factors Influencing The Large-Scale Distribution Of Hg° In The Mexico City Area And Over The North Pacific, Robert W. Talbot, Huiting Mao, Jack E. Dibb, M A. Avery, E V. Browell, G W. Sachse, S Vay, D R. Blake, L Gregory Huey, H Fuelberg Apr 2008

Factors Influencing The Large-Scale Distribution Of Hg° In The Mexico City Area And Over The North Pacific, Robert W. Talbot, Huiting Mao, Jack E. Dibb, M A. Avery, E V. Browell, G W. Sachse, S Vay, D R. Blake, L Gregory Huey, H Fuelberg

Earth Sciences

Gas-phase elemental mercury (Hg°) was measured aboard the NASA DC-8 aircraft during the Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign in spring 2006. Flights were conducted around Mexico City and on two subsequent deployments over the North Pacific based out of Honolulu, Hawaii and Anchorage, Alaska. Data obtained from 0.15–12 km altitude showed that Hg° exhibited a relatively constant vertical profile centered around 100 ppqv. Highly concentrated pollution plumes emanating from the Mexico City urban agglomeration revealed that mixing ratios of Hg° as large as 500 ppqv were related to combustion tracers such as CO, but not SO2 which …

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Validation Of The Aura Microwave Limb Sounder Hnomeasurements, M L. Santee, A Lambert, W G. Read, N J. Livesey, R E. Cofield, D T. Cuddy, W H. Daffer, B J. Drouin, L Froidevaux, R A. Fuller, R F. Jarnot, B W. Knosp, G L. Manney, V S. Perun, W V. Snyder, P C. Stek, R P. Thurstans, P A. Wagner, J W. Waters, G Muscari, R L. De Zafra, Jack E. Dibb, D W. Fahey, P J. Popp, T P. Marcy, K W. Jucks, G C. Toon, R A. Stachnik, P F. Bernath, C D. Boone, K A. Walker, J Urban, D Murtagh Dec 2007

Validation Of The Aura Microwave Limb Sounder Hnomeasurements, M L. Santee, A Lambert, W G. Read, N J. Livesey, R E. Cofield, D T. Cuddy, W H. Daffer, B J. Drouin, L Froidevaux, R A. Fuller, R F. Jarnot, B W. Knosp, G L. Manney, V S. Perun, W V. Snyder, P C. Stek, R P. Thurstans, P A. Wagner, J W. Waters, G Muscari, R L. De Zafra, Jack E. Dibb, D W. Fahey, P J. Popp, T P. Marcy, K W. Jucks, G C. Toon, R A. Stachnik, P F. Bernath, C D. Boone, K A. Walker, J Urban, D Murtagh

Earth Sciences

We assess the quality of the version 2.2 (v2.2) HNO3 measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System Aura satellite. The MLS HNO3 product has been greatly improved over that in the previous version (v1.5), with smoother profiles, much more realistic behavior at the lowest retrieval levels, and correction of a high bias caused by an error in one of the spectroscopy files used in v1.5 processing. The v2.2 HNO3 data are scientifically useful over the range 215 to 3.2 hPa, with single-profile precision of ∼0.7 ppbv throughout. Vertical resolution is 3–4 km …

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Total Depletion Of Hg° In The Upper Troposphere-Lower Stratosphere, R. Talbot, Huiting Mao, Jack E. Dibb, M A. Avery Dec 2007

Total Depletion Of Hg° In The Upper Troposphere-Lower Stratosphere, R. Talbot, Huiting Mao, Jack E. Dibb, M A. Avery

Earth Sciences

Our current understanding of atmospheric mercury lacks fundamental details. Gas phase elemental mercury (Hg°) was measured aboard the NASA DC-8 research aircraft during the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B) conducted in spring 2006 over the North Pacific. Our data confirm efficient chemical cycling of Hg° in the tropopause region and show that it is strongly anti-correlated with O3 there, yielding a tropospheric-stratospheric mixing curve of ∼−0.20 ppqv Hg°/ppbv O3. In addition, we found frequent total depletion of Hg° in upper tropospheric (8–12 km) air masses impacted by stratospheric influence. When O3 mixing ratios were >300 …

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A Summer Time Series Of Particulate Carbon In The Air And Snow At Summit, Greenland, Gayle S.W. Hagler, M Bergin, Eugene A. Smith, Jack E. Dibb Nov 2007

A Summer Time Series Of Particulate Carbon In The Air And Snow At Summit, Greenland, Gayle S.W. Hagler, M Bergin, Eugene A. Smith, Jack E. Dibb

Earth Sciences

Carbonaceous particulate matter is ubiquitous in the lower atmosphere, produced by natural and anthropogenic sources and transported to distant regions, including the pristine and climate-sensitive Greenland Ice Sheet. During the summer of 2006, ambient particulate carbonaceous compounds were characterized on the Greenland Ice Sheet, including the measurement of particulate organic (OC) and elemental (EC) carbon, particulate water-soluble organic carbon (WSOC), particulate absorption coefficient (σap), and particle size-resolved number concentration (PM0.1–1.0). Additionally, parallel ∼50-day time series of water-soluble organic carbon (WSOC), water-insoluble organic carbon (WIOC), and elemental carbon (EC) were quantified at time increments of 4–24 …

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Particulate And Water-Soluble Carbon Measured In Recent Snow At Summit, Greenland, Gayle S.W. Hagler, M Bergin, Eugene A. Smith, Jack E. Dibb, Casey Anderson, Eric J. Steig Aug 2007

Particulate And Water-Soluble Carbon Measured In Recent Snow At Summit, Greenland, Gayle S.W. Hagler, M Bergin, Eugene A. Smith, Jack E. Dibb, Casey Anderson, Eric J. Steig

Earth Sciences

Water-soluble organic carbon (WSOC), waterinsoluble particulate organic carbon (WIOC), and particulate elemental carbon (EC) were measured simultaneously for the first time on the Greenland Ice Sheet in surface snow and in a 3-meter snow pit. Snow pit concentrations reveal that, on average, WSOC makes up the majority (89%) of carbonaceous species, followed by WIOC (10%) and EC (1%). The enhancement of OC relative to EC (ratio 99:1) in Greenland snow suggests that, along with atmospheric particulate matter, gaseous organics contribute to snow-phase OC. Comparison of summer surface snow concentrations in 2006 with past summer snow pit layers (2002 – 2005) …

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Impact Of Multiscale Dynamical Processes And Mixing On The Chemical Composition Of The Upper Troposphere And Lower Stratosphere During The Intercontinental Chemical Transport Experiment–North America, T D. Fairlie, Melody A. Avery, R B. Pierce, J Al-Saadi, Jack E. Dibb, G W. Sachse Aug 2007

Impact Of Multiscale Dynamical Processes And Mixing On The Chemical Composition Of The Upper Troposphere And Lower Stratosphere During The Intercontinental Chemical Transport Experiment–North America, T D. Fairlie, Melody A. Avery, R B. Pierce, J Al-Saadi, Jack E. Dibb, G W. Sachse

Earth Sciences

We use high-frequency in situ observations made from the DC8 to examine fine-scale tracer structure and correlations observed in the upper troposphere and lower stratosphere during INTEX-NA. Two flights of the NASA DC-8 are compared and contrasted. Chemical data from the DC-8 flight on 18 July show evidence for interleaving and mixing of polluted and stratospheric air masses in the vicinity of the subtropical jet in the upper troposphere, while on 2 August the DC-8 flew through a polluted upper troposphere and a lowermost stratosphere that showed evidence of an intrusion of polluted air. We compare data from both flights …

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An Overview Of Snow Photochemistry: Evidence, Mechanisms And Impacts, A M. Grannas, A E. Jones, Jack E. Dibb, M Ammann, Cort Anastasio, H J. Beine, M Bergin, J Bottenheim, C S. Boxe, G Carver, G Chen, J H. Crawford, Florent Domine, M M. Frey, M I. Guzman, D E. Heard, D Helmig, M R. Hoffmann, R E. Honrath, L Gregory Huey, Manuel Hutterli, H W. Jacobi, P Klan, Barry Lefer, J Mcconnell, J Plane, R Sander, J Savarino, P B. Shepson, W R. Simpson, J R. Sodeau, R Von Glasow, R Weller, E W. Wolff, T Zhu Aug 2007

An Overview Of Snow Photochemistry: Evidence, Mechanisms And Impacts, A M. Grannas, A E. Jones, Jack E. Dibb, M Ammann, Cort Anastasio, H J. Beine, M Bergin, J Bottenheim, C S. Boxe, G Carver, G Chen, J H. Crawford, Florent Domine, M M. Frey, M I. Guzman, D E. Heard, D Helmig, M R. Hoffmann, R E. Honrath, L Gregory Huey, Manuel Hutterli, H W. Jacobi, P Klan, Barry Lefer, J Mcconnell, J Plane, R Sander, J Savarino, P B. Shepson, W R. Simpson, J R. Sodeau, R Von Glasow, R Weller, E W. Wolff, T Zhu

Earth Sciences

It has been shown that sunlit snow and ice plays an important role in processing atmospheric species. Photochemical production of a variety of chemicals has recently been reported to occur in snow/ice and the release of these photochemically generated species may significantly impact the chemistry of the overlying atmosphere. Nitrogen oxide and oxidant precursor fluxes have been measured in a number of snow covered environments, where in some cases the emissions significantly impact the overlying boundary layer. For example, photochemical ozone production (such as that occurring in polluted mid-latitudes) of 3-4 ppbv/day has been observed at South Pole, due to …

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Summertime Influence Of Asian Pollution In The Free Troposphere Over North America, Q Liang, L Jaegle, R C. Hudman, S Turquety, D J. Jacob, Melody A. Avery, E V. Browell, G W. Sachse, D R. Blake, William H. Brune, Xinrong Ren, Ronald C. Cohen, Jack E. Dibb, A Fried, H Fuelberg, M Porter, B J. Heikes, Greg Huey, H B. Singh, Paul Wennberg Jun 2007

Summertime Influence Of Asian Pollution In The Free Troposphere Over North America, Q Liang, L Jaegle, R C. Hudman, S Turquety, D J. Jacob, Melody A. Avery, E V. Browell, G W. Sachse, D R. Blake, William H. Brune, Xinrong Ren, Ronald C. Cohen, Jack E. Dibb, A Fried, H Fuelberg, M Porter, B J. Heikes, Greg Huey, H B. Singh, Paul Wennberg

Earth Sciences

We analyze aircraft observations obtained during INTEX-A (1 July to 14 August 2004) to examine the summertime influence of Asian pollution in the free troposphere over North America. By applying correlation analysis and principal component analysis (PCA) to the observations between 6 and 12 km, we find dominant influences from recent convection and lightning (13% of observations), Asia (7%), the lower stratosphere (7%), and boreal forest fires (2%), with the remaining 71% assigned to background. Asian air masses are marked by high levels of CO, O3, HCN, PAN, C2H2, C6H6, methanol, and SO4 2 –. The partitioning of NOy species …

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Biomass Burning And Pollution Aerosol Over North America: Organic Components And Their Influence On Spectral Optical Properties And Humidification Response, A D. Clarke, Cameron Mcnaughton, V Kapustin, Yohei Shinozuka, S G. Howell, Jack E. Dibb, J Zhou, B Anderson, V Brekhovskikh, H Turner, M Pinkerton Jun 2007

Biomass Burning And Pollution Aerosol Over North America: Organic Components And Their Influence On Spectral Optical Properties And Humidification Response, A D. Clarke, Cameron Mcnaughton, V Kapustin, Yohei Shinozuka, S G. Howell, Jack E. Dibb, J Zhou, B Anderson, V Brekhovskikh, H Turner, M Pinkerton

Earth Sciences

Thermal analysis of aerosol size distributions provided size resolved volatility up to temperatures of 400°C during extensive flights over North America (NA) for the INTEX/ICARTT experiment in summer 2004. Biomass burning and pollution plumes identified from trace gas measurements were evaluated for their aerosol physiochemical and optical signatures. Measurements of soluble ionic mass and refractory black carbon (BC) mass, inferred from light absorption, were combined with volatility to identify organic carbon at 400°C (VolatileOC) and the residual or refractory organic carbon, RefractoryOC. This approach characterized distinct constituent mass fractions present in biomass burning and pollution plumes every 5–10 min. Biomass …

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Chemical Data Assimilation Estimates Of Continental U.S. Ozone And Nitrogen Budgets During The Intercontinental Chemical Transport Experiment-North America, R B. Pierce, T Schaack, J Al-Saadi, T D. Fairlie, Chieko Kittaka, Gretchen Lingenfelser, M Natarajan, J R. Olson, Amber Soja, Tom Zapotocny, A Lenzen, M A. Avery, James Stobie, Donald Johnson, Melody A. Avery, G W. Sachse, A M. Thompson, Ronald C. Cohen, Jack E. Dibb, J Crawford, Didier Rault, Randall Martin, Jim Szykman, Jack Fishman Jun 2007

Chemical Data Assimilation Estimates Of Continental U.S. Ozone And Nitrogen Budgets During The Intercontinental Chemical Transport Experiment-North America, R B. Pierce, T Schaack, J Al-Saadi, T D. Fairlie, Chieko Kittaka, Gretchen Lingenfelser, M Natarajan, J R. Olson, Amber Soja, Tom Zapotocny, A Lenzen, M A. Avery, James Stobie, Donald Johnson, Melody A. Avery, G W. Sachse, A M. Thompson, Ronald C. Cohen, Jack E. Dibb, J Crawford, Didier Rault, Randall Martin, Jim Szykman, Jack Fishman

Earth Sciences

Global ozone analyses, based on assimilation of stratospheric profile and ozone column measurements, and NOy predictions from the Real-time Air Quality Modeling System (RAQMS) are used to estimate the ozone and NOy budget over the continental United States during the July-August 2004 Intercontinental Chemical Transport Experiment-North America (INTEX-A). Comparison with aircraft, satellite, surface, and ozonesonde measurements collected during INTEX-A show that RAQMS captures the main features of the global and continental U.S. distribution of tropospheric ozone, carbon monoxide, and NOy with reasonable fidelity. Assimilation of stratospheric profile and column ozone measurements is shown to have a positive impact on the …

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Improving Regional Ozone Modeling Through Systematic Evaluation Of Errors Using The Aircraft Observations During The International Consortium For Atmospheric Research On Transport And Transformation, M Mena-Carrasco, Youhua Tang, Gregory R. Carmichael, Tianfeng Chai, Narisara Thongbongchoo, J Elliott Campbell, S Kulkarni, Larry Horowitz, Jeffrey Vukovich, Melody A. Avery, William H. Brune, Jack E. Dibb, L K. Emmons, F Flocke, Glen Sachse, David Tan, R E. Shetter, R. Talbot, David G. Streets, D R. Blake Jun 2007

Improving Regional Ozone Modeling Through Systematic Evaluation Of Errors Using The Aircraft Observations During The International Consortium For Atmospheric Research On Transport And Transformation, M Mena-Carrasco, Youhua Tang, Gregory R. Carmichael, Tianfeng Chai, Narisara Thongbongchoo, J Elliott Campbell, S Kulkarni, Larry Horowitz, Jeffrey Vukovich, Melody A. Avery, William H. Brune, Jack E. Dibb, L K. Emmons, F Flocke, Glen Sachse, David Tan, R E. Shetter, R. Talbot, David G. Streets, D R. Blake

Earth Sciences

During the operational phase of the ICARTT field experiment in 2004, the regional air quality model STEM showed a strong positive surface bias and a negative upper troposphere bias (compared to observed DC-8 and WP-3 observations) with respect to ozone. After updating emissions from NEI 1999 to NEI 2001 (with a 2004 large point sources inventory update), and modifying boundary conditions, low-level model bias decreases from 11.21 to 1.45 ppbv for the NASA DC-8 observations and from 8.26 to −0.34 for the NOAA WP-3. Improvements in boundary conditions provided by global models decrease the upper troposphere negative ozone bias, while …

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