125 results match your criteria Atmospheric Chemistry And Physics[Journal]

Reappraising the appropriate calculation of a common meteorological quantity: Potential Temperature.

Atmos Chem Phys 2020 Dec;20(24)

Institute for Atmospheric Physics, Johannes Gutenberg University Mainz, Germany.

The potential temperature is a widely used quantity in atmospheric science since it is conserved for dry air's adiabatic changes of state. Its definition involves the specific heat capacity of dry air, which is traditionally assumed as constant. However, the literature provides different values of this allegedly constant parameter, which are reviewed and discussed in this study. Read More

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December 2020

Constraining remote oxidation capacity with ATom observations.

Atmos Chem Phys 2020 Jul 3;20(13):7753-7781. Epub 2020 Jul 3.

Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA.

The global oxidation capacity, defined as the tropospheric mean concentration of the hydroxyl radical (OH), controls the lifetime of reactive trace gases in the atmosphere such as methane and carbon monoxide (CO). Models tend to underestimate the methane lifetime and CO concentrations throughout the troposphere, which is consistent with excessive OH. Approximately half of the oxidation of methane and non-methane volatile organic compounds (VOCs) is thought to occur over the oceans where oxidant chemistry has received little validation due to a lack of observational constraints. Read More

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Aircraft-based inversions quantify the importance of wetlands and livestock for Upper Midwest methane emissions.

Atmos Chem Phys 2021 Jan 25;21(2):951-971. Epub 2021 Jan 25.

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, United States.

We apply airborne measurements across three seasons (summer, winter and spring 2017-2018) in a multi-inversion framework to quantify methane emissions from the US Corn Belt and Upper Midwest, a key agricultural and wetland source region. Combing our seasonal results with prior fall values we find that wetlands are the largest regional methane source (32 %, 20 [16-23] Gg/d), while livestock (enteric/manure; 25 %, 15 [14-17] Gg/d) are the largest anthropogenic source. Natural gas/petroleum, waste/landfills, and coal mines collectively make up the remainder. Read More

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January 2021

Chemical composition, structures, and light absorption of N-containing aromatic compounds emitted from burning wood and charcoal in household cookstoves.

Atmos Chem Phys 2020 Nov;20(22):14077-14090

State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing 210023, China.

N-containing aromatic compounds (NACs) are an important group of light-absorbing molecules in the atmosphere. They are often observed in combustion emissions, but their chemical formulas and structural characteristics remain uncertain. In this study, red oak wood and charcoal fuels were burned in cookstoves using the standard water boiling test (WBT) procedure. Read More

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November 2020

The Acidity of Atmospheric Particles and Clouds.

Atmos Chem Phys 2020 Apr;20(8):4809-4888

Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, H3A 0B9, Canada.

Acidity, defined as pH, is a central component of aqueous chemistry. In the atmosphere, the acidity of condensed phases (aerosol particles, cloud water, and fog droplets) governs the phase partitioning of semi-volatile gases such as HNO, NH, HCl, and organic acids and bases as well as chemical reaction rates. It has implications for the atmospheric lifetime of pollutants, deposition, and human health. Read More

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Correcting model biases of CO in East Asia: impact on oxidant distributions during KORUS-AQ.

Atmos Chem Phys 2020 Dec;20(23):14617-14647

NASA Langley Research Center, Hampton, VA, USA.

Global coupled chemistry-climate models underestimate carbon monoxide (CO) in the Northern Hemisphere, exhibiting a pervasive negative bias against measurements peaking in late winter and early spring. While this bias has been commonly attributed to underestimation of direct anthropogenic and biomass burning emissions, chemical production and loss via OH reaction from emissions of anthropogenic and biogenic volatile organic compounds (VOCs) play an important role. Here we investigate the reasons for this underestimation using aircraft measurements taken in May and June 2016 from the Korea-United States Air Quality (KORUS-AQ) experiment in South Korea and the Air Chemistry Research in Asia (ARIAs) in the North China Plain (NCP). Read More

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December 2020

Evaluating trends and seasonality in modeled PM concentrations using empirical mode decomposition.

Atmos Chem Phys 2020 Nov;20(22):13801-13815

University of Connecticut, Department of Civil and Environmental Engineering, Storrs-Mansfield, CT, USA.

Regional-scale air quality models are being used for studying the sources, composition, transport, transformation, and deposition of fine particulate matter (PM). The availability of decadal air quality simulations provides a unique opportunity to explore sophisticated model evaluation techniques rather than relying solely on traditional operational evaluations. In this study, we propose a new approach for process-based model evaluation of speciated PM using improved complete ensemble empirical mode decomposition with adaptive noise (improved CEEMDAN) to assess how well version 5. Read More

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November 2020

On the relationship between cloud water composition and cloud droplet number concentration.

Atmos Chem Phys 2020 Jul 2;20(13):7645-7665. Epub 2020 Jul 2.

Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, USA.

Aerosol-cloud interactions are the largest source of uncertainty in quantifying anthropogenic radiative forcing. The large uncertainty is, in part, due to the difficulty of predicting cloud microphysical parameters, such as the cloud droplet number concentration (). Even though rigorous first-principle approaches exist to calculate , the cloud and aerosol research community also relies on empirical approaches such as relating to aerosol mass concentration. Read More

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Surprising similarities in model and observational aerosol radiative forcing estimates.

Atmos Chem Phys 2020 Jan 17;20(1):613-623. Epub 2020 Jan 17.

Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, USA.

The radiative forcing from aerosols (particularly through their interaction with clouds) remains one of the most uncertain components of the human forcing of the climate. Observation-based studies have typically found a smaller aerosol effective radiative forcing than in model simulations and were given preferential weighting in the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5). With their own sources of uncertainty, it is not clear that observation-based estimates are more reliable. Read More

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January 2020

Interannual variability and trends of combustion aerosol and dust in major continental outflows revealed by MODIS retrievals and CAM5 simulations during 2003-2017.

Atmos Chem Phys 2020 Jan 3;20(1):139-161. Epub 2020 Jan 3.

Earth Sciences Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA.

Emissions and long-range transport of mineral dust and combustion-related aerosol from burning fossil fuels and biomass vary from year to year, driven by the evolution of the economy and changes in meteorological conditions and environmental regulations. This study offers both satellite and model perspectives on the interannual variability and possible trends of combustion aerosol and dust in major continental outflow regions over the past 15 years (2003-2017). The decade-long record of aerosol optical depth (AOD, denoted as ), separately for combustion aerosol () and dust (), over global oceans is derived from the Collection 6 aerosol products of the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard both Terra and Aqua. Read More

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January 2020

Stratocumulus cloud clearings: statistics from satellites, reanalysis models, and airborne measurements.

Atmos Chem Phys 2020 Apr 21;20(8):4637-4665. Epub 2020 Apr 21.

Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, USA.

This study provides a detailed characterization of stratocumulus clearings off the US West Coast using remote sensing, reanalysis, and airborne in situ data. Ten years (2009-2018) of Geostationary Operational Environmental Satellite (GOES) imagery data are used to quantify the monthly frequency, growth rate of total area (GR), and dimensional characteristics of 306 total clearings. While there is interannual variability, the summer (winter) months experienced the most (least) clearing events, with the lowest cloud fractions being in close proximity to coastal topographical features along the central to northern coast of California, including especially just south of Cape Mendocino and Cape Blanco. Read More

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Predicting secondary organic aerosol phase state and viscosity and its effect on multiphase chemistry in a regional-scale air quality model.

Atmos Chem Phys 2020 Jul;20(12):8201-8225

Department of Environmental Science and Engineering, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27516, USA.

Atmospheric aerosols are a significant public health hazard and have substantial impacts on the climate. Secondary organic aerosols (SOAs) have been shown to phase separate into a highly viscous organic outer layer surrounding an aqueous core. This phase separation can decrease the partitioning of semi-volatile and low-volatile species to the organic phase and alter the extent of acid-catalyzed reactions in the aqueous core. Read More

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Simulation of organic aerosol formation during the CalNex study: updated mobile emissions and secondary organic aerosol parameterization for intermediate-volatility organic compounds.

Atmos Chem Phys 2020 Apr;20(7):4313-4332

Center of Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA.

We describe simulations using an updated version of the Community Multiscale Air Quality model version 5.3 (CMAQ v5.3) to investigate the contribution of intermediate-volatility organic compounds (IVOCs) to secondary organic aerosol (SOA) formation in southern California during the CalNex study. Read More

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Impact of halogen chemistry on summertime air quality in coastal and continental Europe: application of the CMAQ model and implications for regulation.

Atmos Chem Phys 2019 Dec;19(24):15321-15337

Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid 28006, Spain.

Halogen (Cl, Br, and I) chemistry has been reported to influence the formation of secondary air pollutants. Previous studies mostly focused on the impact of chlorine species on air quality over large spatial scales. Very little attention has been paid to the effect of the combined halogen chemistry on air quality over Europe and its implications for control policy. Read More

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December 2019

Modeling stratospheric intrusion and trans-Pacific transport on tropospheric ozone using hemispheric CMAQ during April 2010 - Part 2: Examination of emission impacts based on the higher-order decoupled direct method.

Atmos Chem Phys 2020 Mar;20(6):3397-3413

Department of Marine, Earth, and Atmospheric Sciences (MEAS), North Carolina State University (NCSU), Campus Box 8208, Raleigh, NC 27695, USA.

The state-of-the-science Community Multiscale Air Quality (CMAQ) modeling system, which has recently been extended for hemispheric-scale modeling applications (referred to as H-CMAQ), is applied to study the trans-Pacific transport, a phenomenon recognized as a potential source of air pollution in the US, during April 2010. The results of this analysis are presented in two parts. In the previous paper (Part 1), model evaluation for tropospheric ozone (O) was presented and an air mass characterization method was developed. Read More

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Modeling stratospheric intrusion and trans-Pacific transport on tropospheric ozone using hemispheric CMAQ during April 2010 - Part 1: Model evaluation and air mass characterization for stratosphere-troposphere transport.

Atmos Chem Phys 2020 Mar;20(6):3373-3396

Department of Marine, Earth, and Atmospheric Sciences (MEAS), North Carolina State University (NCSU), Campus Box 8208, Raleigh, NC 27695, USA.

Stratospheric intrusion and trans-Pacific transport have been recognized as a potential source of tropospheric ozone over the US. The state-of-the-science Community Multiscale Air Quality (CMAQ) modeling system has recently been extended for hemispheric-scale modeling applications (referred to as H-CMAQ). In this study, H-CMAQ is applied to study the stratospheric intrusion and trans-Pacific transport during April 2010. Read More

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On the Limit to the Accuracy of Regional-Scale Air Quality Models.

Atmos Chem Phys 2020 Feb;20(3):1627-1639

Center for Environmental Measurement & Modeling, U.S. Environmental Protection Agency, Research Triangle Park, NC.

Regional-scale air pollution models are routinely being used world-wide for research, forecasting air quality, and regulatory purposes. It is well recognized that there are both reducible (systematic) and irreducible (unsystematic) errors in the meteorology-atmospheric chemistry modeling systems. The inherent (random) uncertainty stems from our inability to properly characterize stochastic variations in atmospheric dynamics and chemistry, and from the incommensurability associated with comparisons of the volume-averaged model estimates with point measurements. Read More

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February 2020

Physical properties of secondary photochemical aerosol from OH oxidation of a cyclic siloxane.

Atmos Chem Phys 2019 8;19(3):1649-1664. Epub 2019 Feb 8.

Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, IA, USA.

Cyclic volatile methyl siloxanes (cVMS) are high-production chemicals present in many personal care products. They are volatile, hydrophobic, and relatively long-lived due to slow oxidation kinetics. Evidence from chamber and ambient studies indicates that oxidation products may be found in the condensed aerosol phase. Read More

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February 2019

Dimensionality-reduction techniques for complex mass spectrometric datasets: application to laboratory atmospheric organic oxidation experiments.

Atmos Chem Phys 2020 27;20(2):1021-1041. Epub 2020 Jan 27.

Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, Cambridge, MA, USA.

Oxidation of organic compounds in the atmosphere produces an immensely complex mixture of product species, posing a challenge for both their measurement in laboratory studies and their inclusion in air quality and climate models. Mass spectrometry techniques can measure thousands of these species, giving insight into these chemical processes, but the datasets themselves are highly complex. Data reduction techniques that group compounds in a chemically and kinetically meaningful way provide a route to simplify the chemistry of these systems but have not been systematically investigated. Read More

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January 2020

UV spectroscopic determination of the chlorine monoxide (ClO) / chlorine peroxide (ClOOCl) thermal equilibrium constant.

Atmos Chem Phys 2019 May;19(9):6205-6215

Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.

The thermal equilibrium constant between the chlorine monoxide radical (ClO) and its dimer, chlorine peroxide (ClOOCl), was determined as a function of temperature between 228 and 301K in a discharge flow apparatus using broadband UV absorption spectroscopy. A third-law fit of the equilibrium values determined from the experimental data provides the expression = 2.16 × 10 cm molecule (1σ uncertainty). Read More

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Estimating vehicle carbon dioxide emissions from Boulder, Colorado, using horizontal path-integrated column measurements.

Atmos Chem Phys 2019 ;19

Applied Physics Division, Physical Measurement Laboratory, National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305, USA.

We performed 7.5 weeks of path-integrated concentration measurements of CO, CH, HO, and HDO over the city of Boulder, Colorado. An open-path dual-comb spectrometer simultaneously measured time-resolved data across a reference path, located near the mountains to the west of the city, and across an over-city path that intersected two-thirds of the city, including two major commuter arteries. Read More

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January 2019

Taehwa Research Forest: A receptor site for severe domestic pollution events in Korea during 2016.

Atmos Chem Phys 2019 ;19(7):5051-5067

California Air Resources Board, Sacramento, CA, 95814, USA.

During the May-June 2016 International Cooperative Air Quality Field Study in Korea (KORUS-AQ), light synoptic meteorological forcing facilitated Seoul metropolitan pollution outflow to reach the remote Taehwa Research Forest (TRF) site and cause regulatory exceedances of ozone on 24 days. Two of these severe pollution events are thoroughly examined. The first, occurring on 17 May 2016, tracks transboundary pollution transport exiting eastern China and the Yellow Sea, traversing the Seoul Metropolitan Area (SMA), and then reaching TRF in the afternoon hours with severely polluted conditions. Read More

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January 2019

Composition and light absorption of N-containing aromatic compounds in organic aerosols from laboratory biomass burning.

Atmos Chem Phys 2019 ;19(5):2899-2915

National Risk Management Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, 109 T.W. Alexander Drive, Research Triangle Pak, NC 27711, USA.

This study seeks to understand the compositional details of N-containing aromatic compounds (NACs) emitted during biomass burning (BB) and their contribution to light-absorbing organic carbon (OC), also termed brown carbon (BrC). Three laboratory BB experiments were conducted with two U.S. Read More

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January 2019

Extending the SBUV PMC Data Record with OMPS NP.

Atmos Chem Phys 2019 14;19(11):7913-7925. Epub 2019 Jun 14.

Laboratory for Atmospheric and Space Physics (LASP)/University of Colorado, Boulder, Colorado 80303 USA.

We have utilized Solar Backscatter Ultraviolet (SBUV) instrument measurements of atmospheric radiance to create a 40-year record of polar mesospheric cloud (PMC) behavior. While this series of measurements is nearing its end, we show in this paper that Ozone Mapping and Profiling Suite (OMPS) Nadir Profiler (NP) instruments can be added to the merged SBUV PMC data record. Regression analysis of this extended record shows smaller trends in PMC ice water content (IWC) since approximately 1998, consistent with previous work. Read More

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Intercomparison of atmospheric trace gas dispersion models: Barnett Shale case study.

Atmos Chem Phys 2019 ;19

Special Programs Office, National Institute of Standards and Technology, Gaithersburg, MD, USA.

Greenhouse gas emissions mitigation requires understanding the dominant processes controlling fluxes of these trace gases at increasingly finer spatial and temporal scales. Trace gas fluxes can be estimated using a variety of approaches that translate observed atmospheric species mole fractions into fluxes or emission rates, often identifying the spatial and temporal characteristics of the emission sources as well. Meteorological models are commonly combined with tracer dispersion models to estimate fluxes using an inverse approach that optimizes emissions to best fit the trace gas mole fraction observations. Read More

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January 2019

On the sources and sinks of atmospheric VOCs: an integrated analysis of recent aircraft campaigns over North America.

Atmos Chem Phys 2019 Jul 17;19(14):9097-9123. Epub 2019 Jul 17.

Institute of Arctic & Alpine Research, University of Colorado, Boulder, CO, USA.

We apply a high-resolution chemical transport model (GEOS-Chem CTM) with updated treatment of volatile organic compounds (VOCs) and a comprehensive suite of airborne datasets over North America to (i) characterize the VOC budget and (ii) test the ability of current models to capture the distribution and reactivity of atmospheric VOCs over this region. Biogenic emissions dominate the North American VOC budget in the model, accounting for 70 % and 95 % of annually emitted VOC carbon and reactivity, respectively. Based on current inventories anthropogenic emissions have declined to the point where biogenic emissions are the dominant summertime source of VOC reactivity even in most major North American cities. Read More

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Evaluation of global simulations of aerosol particle and cloud condensation nuclei number, with implications for cloud droplet formation.

Atmos Chem Phys 2019 Jul 8;19(13):8591-8617. Epub 2019 Jul 8.

Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland.

A total of 16 global chemistry transport models and general circulation models have participated in this study; 14 models have been evaluated with regard to their ability to reproduce the near-surface observed number concentration of aerosol particles and cloud condensation nuclei (CCN), as well as derived cloud droplet number concentration (CDNC). Model results for the period 2011-2015 are compared with aerosol measurements (aerosol particle number, CCN and aerosol particle composition in the submicron fraction) from nine surface stations located in Europe and Japan. The evaluation focuses on the ability of models to simulate the average across time state in diverse environments and on the seasonal and short-term variability in the aerosol properties. Read More

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Ozone source apportionment during peak summer events over southwestern Europe.

Atmos Chem Phys 2019 Apr;19(8):5467-5494

Earth Sciences Department, Barcelona Supercomputing Center, BSC, c/Jordi Girona, 29, 08034 Barcelona, Spain.

It is well established that in Europe, high O concentrations are most pronounced in southern/Mediterranean countries due to the more favourable climatological conditions for its formation. However, the contribution of the different sources of precursors to O formation within each country relative to the imported (regional and hemispheric) O is poorly quantified. This lack of quantitative knowledge prevents local authorities from effectively designing plans that reduce the exceedances of the O target value set by the European air quality directive. Read More

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Modelling black carbon absorption of solar radiation: combining external and internal mixing assumptions.

Atmos Chem Phys 2019 7;19(1):181-204. Epub 2019 Jan 7.

Joint Research Centre (JRC), European Commission, Ispra (VA), 21027, Italy.

An accurate simulation of the absorption properties is key for assessing the radiative effects of aerosol on meteorology and climate. The representation of how chemical species are mixed inside the particles (the mixing state) is one of the major uncertainty factors in the assessment of these effects. Here we compare aerosol optical properties simulations over Europe and North America, coordinated in the framework of the third phase of the Air Quality Model Evaluation International Initiative (AQMEII), to 1 year of AERONET sunphotometer retrievals, in an attempt to identify a mixing state representation that better reproduces the observed single scattering albedo and its spectral variation. Read More

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January 2019

Seasonal ozone vertical profiles over North America using the AQMEII3 group of air quality models: model inter-comparison and stratospheric intrusions.

Atmos Chem Phys 2018 2;18(19):13925-13945. Epub 2018 Oct 2.

Ramboll, 773 San Marin Dr., Suite 2115, Novato, CA 94945, USA.

This study evaluates simulated vertical ozone profiles produced in the framework of the third phase of the Air Quality Model Evaluation International Initiative (AQMEII3) against ozonesonde observations in North America for the year 2010. Four research groups from the United States (US) and Europe have provided modeled ozone vertical profiles to conduct this analysis. Because some of the modeling systems differ in their meteorological drivers, wind speed and temperature are also included in the analysis. Read More

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October 2018