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


Opportunistic experiments to constrain aerosol effective radiative forcing.

Atmos Chem Phys 2022 Jan 17;22(1):641-674. Epub 2022 Jan 17.

Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK.

Aerosol-cloud interactions (ACIs) are considered to be the most uncertain driver of present-day radiative forcing due to human activities. The nonlinearity of cloud-state changes to aerosol perturbations make it challenging to attribute causality in observed relationships of aerosol radiative forcing. Using correlations to infer causality can be challenging when meteorological variability also drives both aerosol and cloud changes independently. Read More

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January 2022

Modeling secondary organic aerosol formation from volatile chemical products.

Atmos Chem Phys 2021 Dec;21(24):18247-18261

Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC 27711.

Volatile chemical products (VCPs) are commonly-used consumer and industrial items that are an important source of anthropogenic emissions. Organic compounds from VCPs evaporate on atmospherically relevant time scales and include many species that are secondary organic aerosol (SOA) precursors. However, the chemistry leading to SOA, particularly that of intermediate volatility organic compounds (IVOCs), has not been fully represented in regional-scale models such as the Community Multiscale Air Quality (CMAQ) model, which tend to underpredict SOA concentrations in urban areas. Read More

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December 2021

Unraveling pathways of elevated ozone induced by the 2020 lockdown in Europe by an observationally constrained regional model using TROPOMI.

Atmos Chem Phys 2021 Dec;21:1-19

Atomic and Molecular Physics (AMP) Division, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.

Questions about how emissions are changing during the COVID-19 lockdown periods cannot be answered by observations of atmospheric trace gas concentrations alone, in part due to simultaneous changes in atmospheric transport, emissions, dynamics, photochemistry, and chemical feedback. A chemical transport model simulation benefiting from a multi-species inversion framework using well-characterized observations should differentiate those influences enabling to closely examine changes in emissions. Accordingly, we jointly constrain NO and VOC emissions using well-characterized TROPOspheric Monitoring Instrument (TROPOMI) HCHO and NO columns during the months of March, April, and May 2020 (lockdown) and 2019 (baseline). Read More

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December 2021

Technical note: AQMEII4 Activity 1: evaluation of wet and dry deposition schemes as an integral part of regional-scale air quality models.

Atmos Chem Phys 2021 Oct;21(20):1-15663

Leibniz Institute for Tropospheric Research, Leipzig, Germany.

We present in this technical note the research protocol for phase 4 of the Air Quality Model Evaluation International Initiative (AQMEII4). This research initiative is divided into two activities, collectively having three goals: (i) to define the current state of the science with respect to representations of wet and especially dry deposition in regional models, (ii) to quantify the extent to which different dry deposition parameterizations influence retrospective air pollutant concentration and flux predictions, and (iii) to identify, through the use of a common set of detailed diagnostics, sensitivity simulations, model evaluation, and reduction of input uncertainty, the specific causes for the current range of these predictions. Activity 1 is dedicated to the diagnostic evaluation of wet and dry deposition processes in regional air quality models (described in this paper), and Activity 2 to the evaluation of dry deposition point models against ozone flux measurements at multiple towers with multiyear observations (to be described in future submissions as part of the special issue on AQMEII4). Read More

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October 2021

Aerosol responses to precipitation along North American air trajectories arriving at Bermuda.

Atmos Chem Phys 2021 Nov;21(21):16121-16141

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

North American pollution outflow is ubiquitous over the western North Atlantic Ocean, especially in winter, making this location a suitable natural laboratory for investigating the impact of precipitation on aerosol particles along air mass trajectories. We take advantage of observational data collected at Bermuda to seasonally assess the sensitivity of aerosol mass concentrations and volume size distributions to accumulated precipitation along trajectories (APT). The mass concentration of particulate matter with aerodynamic diameter less than 2. Read More

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November 2021

Improving the representation of HONO chemistry in CMAQ and examining its impact on haze over China.

Atmos Chem Phys 2021 Oct;21(20):15809-15826

State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.

We compare Community Multiscale Air Quality (CMAQ) model predictions with measured nitrous acid (HONO) concentrations in Beijing, China for December 2015. The model with the existing HONO chemistry in CMAQ severely under-estimates the observed HONO concentrations with a normalized mean bias of -97%. We revise the HONO chemistry in the model by implementing six additional heterogeneous reactions in the model: reaction of nitrogen dioxide (NO) on ground surfaces, reaction of NO on aerosol surfaces, reaction of NO on soot surfaces, photolysis of aerosol nitrate, nitric acid displacement reaction, and hydrochloric acid displacement reaction. Read More

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October 2021

Observations of supermicron-sized aerosols originating from biomass burning in southern Central Africa.

Atmos Chem Phys 2021 Sep 6;21(19):14815-14831. Epub 2021 Oct 6.

Universities Space Research Association/NASA Ames Research Center, Moffett Field, Mountain View, CA, USA.

During the 3 years of the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) campaign, the NASA Orion P-3 was equipped with a 2D stereo (2D-S) probe that imaged particles with maximum dimension () ranging from 10 < < 1280 μm. The 2D-S recorded supermicron-sized aerosol particles (SAPs) outside of clouds within biomass burning plumes during flights over the southeastern Atlantic off Africa's coast. Numerous SAPs with 10 < < 1520 μm were observed in 2017 and 2018 at altitudes between 1230 and 4000 m, 1000 km from the coastline, mostly between 7-11° S. Read More

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September 2021

Acidity and the multiphase chemistry of atmospheric aqueous particles and clouds.

Atmos Chem Phys 2021 Sep;21(17)

Department of Chemical Engineering, Columbia University, New York, NY 10027, USA.

The acidity of aqueous atmospheric solutions is a key parameter driving both the partitioning of semi-volatile acidic and basic trace gases and their aqueous-phase chemistry. In addition, the acidity of atmospheric aqueous phases, e.g. Read More

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September 2021

Atmospheric conditions and composition that influence PM oxidative potential in Beijing, China.

Atmos Chem Phys 2021 Apr;21(7):5549-5573

Department of Environmental Sciences, University of Basel, Basel, Switzerland.

Epidemiological studies have consistently linked exposure to PM with adverse health effects. The oxidative potential (OP) of aerosol particles has been widely suggested as a measure of their potential toxicity. Several acellular chemical assays are now readily employed to measure OP; however, uncertainty remains regarding the atmospheric conditions and specific chemical components of PM that drive OP. Read More

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Cloud drop number concentrations over the western North Atlantic Ocean: seasonal cycle, aerosol interrelationships, and other influential factors.

Atmos Chem Phys 2021 Jul 13;21(13):10499-10526. Epub 2021 Jul 13.

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

Cloud drop number concentrations ( ) over the western North Atlantic Ocean (WNAO) are generally highest during the winter (DJF) and lowest in summer (JJA), in contrast to aerosol proxy variables (aerosol optical depth, aerosol index, surface aerosol mass concentrations, surface cloud condensation nuclei (CCN) concentrations) that generally peak in spring (MAM) and JJA with minima in DJF. Using aircraft, satellite remote sensing, ground-based in situ measurement data, and reanalysis data, we characterize factors explaining the divergent seasonal cycles and furthermore probe into factors influencing on seasonal timescales. The results can be summarized well by features most pronounced in DJF, including features associated with cold-air outbreak (CAO) conditions such as enhanced values of CAO index, planetary boundary layer height (PBLH), low-level liquid cloud fraction, and cloud-top height, in addition to winds aligned with continental outflow. Read More

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Reactive organic carbon emissions from volatile chemical products.

Atmos Chem Phys 2021 Mar;21(6):5079-5100

Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.

Volatile chemical products (VCPs) are an increasingly important source of anthropogenic reactive organic carbon (ROC) emissions. Among these sources are everyday items, such as personal care products, general cleaners, architectural coatings, pesticides, adhesives, and printing inks. Here, we develop VCPy, a new framework to model organic emissions from VCPs throughout the United States, including spatial allocation to regional and local scales. Read More

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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

Differences in fine particle chemical composition on clear and cloudy days.

Atmos Chem Phys 2020 ;20(19)

Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC 27709.

Clouds are prevalent and alter PM mass and chemical composition. Cloud-affected satellite retrievals are often removed from data products, hindering estimates of tropospheric chemical composition during cloudy times. We examine surface fine particulate matter (PM) chemical constituent concentrations in the Interagency Monitoring of PROtected Visual Environments network during Cloudy and Clear Sky times defined using Moderate Resolution Imaging Spectroradiometer (MODIS) cloud flags from 2010-2014 with a focus on differences in particle hygroscopicity and aerosol liquid water (ALW). Read More

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January 2020