Physical Sciences and Mathematics | Open Access Articles

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

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

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 (σ_ap), and particle size-resolved number concentration (PM_0.1–1.0). 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

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

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

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

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

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

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

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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Reactive Nitrogen Distribution And Partitioning In The North American Troposphere And Lowermost Stratosphere, H B. Singh, L Salas, D Herlth, R Koyler, M A. Avery, J H. Crawford, R B. Pierce, Glen Sachse, D R. Blake, Ronald C. Cohen, T H. Bertram, A E. Perring, Paul J. Wooldridge, Jack E. Dibb, L Gregory Huey, R C. Hudman, S Turquety, L K. Emmons, F Flocke, Youhua Tang, Gregory R. Carmichael, Larry Horowitz

Earth Sciences

A comprehensive group of reactive nitrogen species (NO, NO₂, HNO₃, HO₂NO₂, PANs, alkyl nitrates, and aerosol-NO₃⁻) were measured over North America during July/August 2004 from the NASA DC-8 platform (0.1–12 km). Nitrogen containing tracers of biomass combustion (HCN and CH₃CN) were also measured along with a host of other gaseous (CO, VOC, OVOC, halocarbon) and aerosol tracers. Clean background air as well as air with influences from biogenic emissions, anthropogenic pollution, biomass combustion, convection, lightning, and the stratosphere was sampled over the continental United States, the Atlantic, …

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Surface And Lightning Sources Of Nitrogen Oxides Over The United States: Magnitudes, Chemical Evolution, And Outflow, R C. Hudman, D J. Jacob, S Turquety, Eric M. Leibensperger, L T. Murray, S Wu, A B. Gilliland, M A. Avery, T H. Bertram, William H. Brune, Ronald C. Cohen, Jack E. Dibb, F Flocke, A Fried, J S. Holloway, J A. Neuman, R Orville, A E. Perring, Xinrong Ren, G W. Sachse, H B. Singh, Aaron L. Swanson, Paul J. Wooldridge

Earth Sciences

We use observations from two aircraft during the ICARTT campaign over the eastern United States and North Atlantic during summer 2004, interpreted with a global 3-D model of tropospheric chemistry (GEOS-Chem) to test current understanding of regional sources, chemical evolution, and export of NOx. The boundary layer NOx data provide top-down verification of a 50% decrease in power plant and industry NOx emissions over the eastern United States between 1999 and 2004. Observed NOx concentrations at 8–12 km altitude were 0.55 ± 0.36 ppbv, much larger than in previous U.S. aircraft campaigns (ELCHEM, SUCCESS, SONEX) though consistent with data from …

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Influence Of Lateral And Top Boundary Conditions On Regional Air Quality Prediction: A Multiscale Study Coupling Regional And Global Chemical Transport Models, Youhua Tang, Gregory R. Carmichael, Narisara Thongbongchoo, Tianfeng Chai, Larry Horowitz, R B. Pierce, J Al-Saadi, G G. Pfister, Jeffrey Vukovich, Melody A. Avery, Glen Sachse, Thomas B. Ryerson, J S. Holloway, E L. Atlas, F Flocke, Rodney J. Weber, L Gregory Huey, Jack E. Dibb, David G. Streets, William H. Brune

Earth Sciences

The sensitivity of regional air quality model to various lateral and top boundary conditions is studied at 2 scales: a 60 km domain covering the whole USA and a 12 km domain over northeastern USA. Three global models (MOZART-NCAR, MOZART-GFDL and RAQMS) are used to drive the STEM-2K3 regional model with time-varied lateral and top boundary conditions (BCs). The regional simulations with different global BCs are examined using ICARTT aircraft measurements performed in the summer of 2004, and the simulations are shown to be sensitive to the boundary conditions from the global models, especially for relatively long-lived species, like CO …

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Aerosol Major Ion Record At Mount Washington, E V. Fischer, L D. Ziemba, R. Talbot, Jack E. Dibb, Robert J. Griffin, L Husain, A N. Grant

Earth Sciences

This study examined the seasonal cycles and regional-scale meteorological controls on the chemical properties of bulk aerosols collected from 1999 to 2004 at Mount Washington, the highest peak in the northeastern United States. The concentrations of NH₄⁺ and SO₄²⁻ peaked during summer months. The pattern for aerosol NO₃⁻ was more complicated with relatively high median concentrations characterizing spring and summer months, but with major elevated events occurring during fall, winter, and spring. The seasonal relationship between NH₄⁺ and SO₄²⁻ indicated that during warmer months a mixture of (NH₄) …

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Full-Text Articles in Physical Sciences and Mathematics

Earth Sciences

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

Earth Sciences

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

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

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

Earth Sciences

Earth Sciences

Earth Sciences

Earth Sciences

Earth Sciences

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Earth Sciences

Earth Sciences

Aerosol Major Ion Record At Mount Washington, E V. Fischer, L D. Ziemba, R. Talbot, Jack E. Dibb, Robert J. Griffin, L Husain, A N. Grant

Earth Sciences