scholarly journals Model evaluation of marine primary organic aerosol emission schemes

2012 ◽  
Vol 12 (5) ◽  
pp. 12853-12883 ◽  
Author(s):  
B. Gantt ◽  
M. S. Johnson ◽  
N. Meskhidze ◽  
J. Sciare ◽  
J. Ovadnevaite ◽  
...  
Keyword(s):  
Model Comparison ◽  
Transport Model ◽  
Organic Aerosol ◽  
Sea Spray ◽  
Mean Values ◽  
Chl A ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Aerosol Emission ◽  
Sea Spray Aerosol

Abstract. In this study, five different marine primary organic aerosol (POA) emission schemes have been evaluated using the GEOS-Chem chemical transport model in order to provide guidance for their implementation in air quality and climate models. These emission schemes, categorized in two groups based on varying dependences of chlorophyll a concentration ([chl a]) and 10 m wind speed (U10), have large differences in their magnitude, spatial distribution, and seasonality. Model comparison with weekly and monthly mean values of the organic aerosol mass concentration at two coastal sites shows that the source function exclusively related to [chl a] does a better job replicating surface observations. Sensitivity simulations of the sea spray-based parameterizations show that improved predictions of the seasonality of the marine POA concentrations can be achieved by varying the U10 and [chl a] dependence of the organic mass fraction of sea spray aerosol. A top-down estimate of submicron marine POA emissions based on the parameterization that compares best to the observed weekly and monthly mean values of marine organic aerosol surface concentrations has a global average emission rate of 6.3 Tg yr−1. Evaluation of existing marine POA source functions against a case study during which marine POA contributed the major fraction of submicron aerosol mass shows that none of the existing parameterizations are able to reproduce the hourly-averaged observations. Our calculations suggest that in order to capture episodic events in submicron marine POA concentration over the ocean, new source functions need to be developed that are grounded in the physical processes unique to the organic fraction of sea spray aerosol.

scholarly journals Model evaluation of marine primary organic aerosol emission schemes

2012 ◽  
Vol 12 (18) ◽  
pp. 8553-8566 ◽  
Author(s):  
B. Gantt ◽  
M. S. Johnson ◽  
N. Meskhidze ◽  
J. Sciare ◽  
J. Ovadnevaite ◽  
...  
Keyword(s):  
Model Comparison ◽  
Transport Model ◽  
Organic Aerosol ◽  
Sea Spray ◽  
Mean Values ◽  
Chl A ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Aerosol Emission ◽  
Sea Spray Aerosol

Abstract. In this study, several marine primary organic aerosol (POA) emission schemes have been evaluated using the GEOS-Chem chemical transport model in order to provide guidance for their implementation in air quality and climate models. These emission schemes, based on varying dependencies of chlorophyll a concentration ([chl a]) and 10 m wind speed (U10), have large differences in their magnitude, spatial distribution, and seasonality. Model comparison with weekly and monthly mean values of the organic aerosol mass concentration at two coastal sites shows that the source function exclusively related to [chl a] does a better job replicating surface observations. Sensitivity simulations in which the negative U10 and positive [chl a] dependence of the organic mass fraction of sea spray aerosol are enhanced show improved prediction of the seasonality of the marine POA concentrations. A top-down estimate of submicron marine POA emissions based on the parameterization that compares best to the observed weekly and monthly mean values of marine organic aerosol surface concentrations has a global average emission rate of 6.3 Tg yr−1. Evaluation of existing marine POA source functions against a case study during which marine POA contributed the major fraction of submicron aerosol mass shows that none of the existing parameterizations are able to reproduce the hourly-averaged observations. Our calculations suggest that in order to capture episodic events and short-term variability in submicron marine POA concentration over the ocean, new source functions need to be developed that are grounded in the physical processes unique to the organic fraction of sea spray aerosol.

scholarly journals Effect of primary organic sea spray emissions on cloud condensation nuclei concentrations

2012 ◽  
Vol 12 (1) ◽  
pp. 89-101 ◽  
Author(s):  
D. M. Westervelt ◽  
R. H. Moore ◽  
A. Nenes ◽  
P. J. Adams
Keyword(s):  
Surface Tension ◽  
Southern Ocean ◽  
Source Function ◽  
Cloud Condensation Nuclei ◽  
Organic Aerosol ◽  
Sea Salt ◽  
Sea Spray ◽  
Aerosol Emission ◽  
Sea Spray Aerosol ◽  
Surfactant Effects

Abstract. This work estimates the primary marine organic aerosol global emission source and its impact on cloud condensation nuclei (CCN) concentrations by implementing an organic sea spray source function into a series of global aerosol simulations. The source function assumes that a fraction of the sea spray emissions, depending on the local chlorophyll concentration, is organic matter in place of sea salt. Effect on CCN concentrations (at 0.2% supersaturation) is modeled using the Two-Moment Aerosol Sectional (TOMAS) microphysics algorithm coupled to the GISS II-prime general circulation model. The presence of organics affects CCN activity in competing ways: by reducing the amount of solute available in the particle and decreasing surface tension of CCN. To model surfactant effects, surface tension depression data from seawater samples taken near the Georgia coast were applied as a function of carbon concentrations. A global marine organic aerosol emission rate of 17.7 Tg C yr−1 is estimated from the simulations. Marine organics exert a localized influence on CCN(0.2%) concentrations, decreasing regional concentrations by no more than 5% and by less than 0.5% over most of the globe, assuming direct replacement of sea salt aerosol with organic aerosol. The decrease in CCN concentrations results from the fact that the decrease in particle solute concentration outweighs the organic surfactant effects. The low sensitivity of CCN(0.2%) to the marine organic emissions is likely due to the small compositional changes: the mass fraction of OA in accumulation mode aerosol increases by only ~15% in a biologically active region of the Southern Ocean. To test the sensitivity to uncertainty in the sea spray emissions process, we relax the assumption that sea spray aerosol number and mass remain fixed and instead can add to sea spray emissions rather than replace existing sea salt. In these simulations, we find that marine organic aerosol can increase CCN by up to 50% in the Southern Ocean and 3.7% globally during the austral summer. This vast difference in CCN impact highlights the need for further observational exploration of the sea spray aerosol emission process as well as evaluation and development of model parameterizations.

scholarly journals Implementing marine organic aerosols into the GEOS-Chem model

2015 ◽  
Vol 8 (3) ◽  
pp. 619-629 ◽  
Author(s):  
B. Gantt ◽  
M. S. Johnson ◽  
M. Crippa ◽  
A. S. H. Prévôt ◽  
N. Meskhidze
Keyword(s):  
Cloud Condensation Nuclei ◽  
Organic Aerosols ◽  
Field Studies ◽  
Organic Aerosol ◽  
Tropospheric Chemistry ◽  
Surface Mass ◽  
Earth Observing System ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Aerosol Emission

Abstract. Marine-sourced organic aerosols (MOAs) have been shown to play an important role in tropospheric chemistry by impacting surface mass, cloud condensation nuclei, and ice nuclei concentrations over remote marine and coastal regions. In this work, an online marine primary organic aerosol emission parameterization, designed to be used for both global and regional models, was implemented into the GEOS-Chem (Global Earth Observing System Chemistry) model. The implemented emission scheme improved the large underprediction of organic aerosol concentrations in clean marine regions (normalized mean bias decreases from −79% when using the default settings to −12% when marine organic aerosols are added). Model predictions were also in good agreement (correlation coefficient of 0.62 and normalized mean bias of −36%) with hourly surface concentrations of MOAs observed during the summertime at an inland site near Paris, France. Our study shows that MOAs have weaker coastal-to-inland concentration gradients than sea-salt aerosols, leading to several inland European cities having >10% of their surface submicron organic aerosol mass concentration with a marine source. The addition of MOA tracers to GEOS-Chem enabled us to identify the regions with large contributions of freshly emitted or aged aerosol having distinct physicochemical properties, potentially indicating optimal locations for future field studies.

scholarly journals Implementing marine organic aerosols into the GEOS-Chem model

2014 ◽  
Vol 7 (5) ◽  
pp. 5965-5992
Author(s):  
B. Gantt ◽  
M. S. Johnson ◽  
M. Crippa ◽  
A. S. H. Prévôt ◽  
N. Meskhidze
Keyword(s):  
Cloud Condensation Nuclei ◽  
Organic Aerosols ◽  
Field Studies ◽  
Organic Aerosol ◽  
Tropospheric Chemistry ◽  
Surface Mass ◽  
Ice Nuclei ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Aerosol Emission

Abstract. Marine organic aerosols (MOA) have been shown to play an important role in tropospheric chemistry by impacting surface mass, cloud condensation nuclei, and ice nuclei concentrations over remote marine and coastal regions. In this work, an online marine primary organic aerosol emission parameterization, designed to be used for both global and regional models, was implemented into the GEOS-Chem model. The implemented emission scheme improved the large underprediction of organic aerosol concentrations in clean marine regions (normalized mean bias decreases from −79% when using the default settings to −12% when marine organic aerosols are added). Model predictions were also in good agreement (correlation coefficient of 0.62 and normalized mean bias of −36%) with hourly surface concentrations of MOA observed during the summertime at an inland site near Paris, France. Our study shows that MOA have weaker coastal-to-inland concentration gradients than sea-salt aerosols, leading to several inland European cities having > 10% of their surface submicron organic aerosol mass concentration with a marine source. The addition of MOA tracers to GEOS-Chem enabled us to identify the regions with large contributions of freshly-emitted or aged aerosol having distinct physicochemical properties, potentially indicating optimal locations for future field studies.

scholarly journals Influence of the aerosol solar extinction on photochemistry during the 2010 Russian wildfires episode

2015 ◽  
Vol 15 (19) ◽  
pp. 10983-10998 ◽  
Author(s):  
J. C. Péré ◽  
B. Bessagnet ◽  
V. Pont ◽  
M. Mallet ◽  
F. Minvielle
Keyword(s):  
Transport Model ◽  
Regional Scale ◽  
Model Performance ◽  
Surface Concentration ◽  
Near Surface ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Air Quality Measurements ◽  
Photolysis Rates ◽  
Optical Module

Abstract. In this work, impact of aerosol solar extinction on the photochemistry over eastern Europe during the 2010 wildfires episode is discussed for the period from 5 to 12 August 2010, which coincides to the peak of fire activity. The methodology is based on an online coupling between the chemistry-transport model CHIMERE (extended by an aerosol optical module) and the radiative transfer code TUV. Results of simulations indicate an important influence of the aerosol solar extinction, in terms of intensity and spatial extent, with a reduction of the photolysis rates of NO2 and O3 up to 50 % (in daytime average) along the aerosol plume transport. At a regional scale, these changes in photolysis rates lead to a 3–15 % increase in the NO2 daytime concentration and to an ozone reduction near the surface of 1–12 %. The ozone reduction is shown to occur over the entire boundary layer, where aerosols are located. Also, the total aerosol mass concentration (PM10) is shown to be decreased by 1–2 %, on average during the studied period, caused by a reduced formation of secondary aerosols such as sulfates and secondary organics (4–10 %) when aerosol impact on photolysis rates is included. In terms of model performance, comparisons of simulations with air quality measurements at Moscow indicate that an explicit representation of aerosols interaction with photolysis rates tend to improve the estimation of the near-surface concentration of ozone and nitrogen dioxide as well as the formation of inorganic aerosol species such as ammonium, nitrates and sulfates.

scholarly journals Gaseous chemistry and aerosol mechanism developments for version 3.5.1 of the online regional model, WRF-Chem

2014 ◽  
Vol 7 (6) ◽  
pp. 2557-2579 ◽  
Author(s):  
S. Archer-Nicholls ◽  
D. Lowe ◽  
S. Utembe ◽  
J. Allan ◽  
R. A. Zaveri ◽  
...  
Keyword(s):  
Gas Phase ◽  
Chemical Mechanism ◽  
Reduced Form ◽  
Sea Spray ◽  
Wind Fields ◽  
Aerosol Composition ◽  
Aerosol Emission ◽  
Sea Spray Aerosol ◽  
The Impact ◽  
Phase Chemical

Abstract. We have made a number of developments to the Weather, Research and Forecasting model coupled with Chemistry (WRF-Chem), with the aim of improving model prediction of trace atmospheric gas-phase chemical and aerosol composition, and of interactions between air quality and weather. A reduced form of the Common Reactive Intermediates gas-phase chemical mechanism (CRIv2-R5) has been added, using the Kinetic Pre-Processor (KPP) interface, to enable more explicit simulation of VOC degradation. N2O5 heterogeneous chemistry has been added to the existing sectional MOSAIC aerosol module, and coupled to both the CRIv2-R5 and existing CBM-Z gas-phase schemes. Modifications have also been made to the sea-spray aerosol emission representation, allowing the inclusion of primary organic material in sea-spray aerosol. We have worked on the European domain, with a particular focus on making the model suitable for the study of nighttime chemistry and oxidation by the nitrate radical in the UK atmosphere. Driven by appropriate emissions, wind fields and chemical boundary conditions, implementation of the different developments are illustrated, using a modified version of WRF-Chem 3.4.1, in order to demonstrate the impact that these changes have in the Northwest European domain. These developments are publicly available in WRF-Chem from version 3.5.1 onwards.

scholarly journals Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements

2015 ◽  
Vol 15 (20) ◽  
pp. 11807-11833 ◽  
Author(s):  
W. W. Hu ◽  
P. Campuzano-Jost ◽  
B. B. Palm ◽  
D. A. Day ◽  
A. M. Ortega ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Secondary Organic Aerosol ◽  
Transport Model ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Chemical Transport Model ◽  
Aerosol Mass Spectrometer ◽  
Aerosol Mass ◽  
Multiple Field

Abstract. Substantial amounts of secondary organic aerosol (SOA) can be formed from isoprene epoxydiols (IEPOX), which are oxidation products of isoprene mainly under low-NO conditions. Total IEPOX-SOA, which may include SOA formed from other parallel isoprene oxidation pathways, was quantified by applying positive matrix factorization (PMF) to aerosol mass spectrometer (AMS) measurements. The IEPOX-SOA fractions of organic aerosol (OA) in multiple field studies across several continents are summarized here and show consistent patterns with the concentration of gas-phase IEPOX simulated by the GEOS-Chem chemical transport model. During the Southern Oxidant and Aerosol Study (SOAS), 78 % of PMF-resolved IEPOX-SOA is accounted by the measured IEPOX-SOA molecular tracers (2-methyltetrols, C5-Triols, and IEPOX-derived organosulfate and its dimers), making it the highest level of molecular identification of an ambient SOA component to our knowledge. An enhanced signal at C5H6O+ (m/z 82) is found in PMF-resolved IEPOX-SOA spectra. To investigate the suitability of this ion as a tracer for IEPOX-SOA, we examine fC5H6O (fC5H6O= C5H6O+/OA) across multiple field, chamber, and source data sets. A background of ~ 1.7 ± 0.1 ‰ (‰ = parts per thousand) is observed in studies strongly influenced by urban, biomass-burning, and other anthropogenic primary organic aerosol (POA). Higher background values of 3.1 ± 0.6 ‰ are found in studies strongly influenced by monoterpene emissions. The average laboratory monoterpene SOA value (5.5 ± 2.0 ‰) is 4 times lower than the average for IEPOX-SOA (22 ± 7 ‰), which leaves some room to separate both contributions to OA. Locations strongly influenced by isoprene emissions under low-NO levels had higher fC5H6O (~ 6.5 ± 2.2 ‰ on average) than other sites, consistent with the expected IEPOX-SOA formation in those studies. fC5H6O in IEPOX-SOA is always elevated (12–40 ‰) but varies substantially between locations, which is shown to reflect large variations in its detailed molecular composition. The low fC5H6O (< 3 ‰) reported in non-IEPOX-derived isoprene-SOA from chamber studies indicates that this tracer ion is specifically enhanced from IEPOX-SOA, and is not a tracer for all SOA from isoprene. We introduce a graphical diagnostic to study the presence and aging of IEPOX-SOA as a triangle plot of fCO2 vs. fC5H6O. Finally, we develop a simplified method to estimate ambient IEPOX-SOA mass concentrations, which is shown to perform well compared to the full PMF method. The uncertainty of the tracer method is up to a factor of ~ 2, if the fC5H6O of the local IEPOX-SOA is not available. When only unit mass-resolution data are available, as with the aerosol chemical speciation monitor (ACSM), all methods may perform less well because of increased interferences from other ions at m/z 82. This study clarifies the strengths and limitations of the different AMS methods for detection of IEPOX-SOA and will enable improved characterization of this OA component.

scholarly journals Determining the link between hygroscopicity and composition for semi-volatile aerosol species

2018 ◽  
Vol 11 (7) ◽  
pp. 4361-4372 ◽  
Author(s):  
Joel Alroe ◽  
Luke T. Cravigan ◽  
Marc D. Mallet ◽  
Zoran D. Ristovski ◽  
Branka Miljevic ◽  
...  
Keyword(s):  
Sampling Technique ◽  
Organic Aerosol ◽  
Marine Aerosol ◽  
Aerosol Mass Spectrometer ◽  
Aerosol Mass ◽  
Coastal Marine ◽  
Bypass Line ◽  
Sea Spray Aerosol ◽  
Aerosol Properties ◽  
Cape Grim

Abstract. Internally and externally mixed aerosols present significant challenges in assessing the hygroscopicity of each aerosol component. This study presents a new sampling technique which uses differences in volatility to separate mixtures and directly examine their respective composition and hygroscopic contribution. A shared thermodenuder and unheated bypass line are continuously cycled between an aerosol mass spectrometer and a volatility and hygroscopicity tandem differential mobility analyser, allowing real-time comparative analysis of heated and unheated aerosol properties. Measurements have been taken of both chamber-generated secondary organic aerosol and coastal marine aerosol at Cape Grim, Australia, to investigate system performance under diverse conditions. Despite rapidly changing aerosol properties and the need to restrict analysis to a narrow size range, the former experiment separated the hygroscopic influences of ammonium sulfate and two distinct organic components with similar oxygen to carbon ratios but different volatilities. Analysis of the marine aerosol revealed an external mixture of non-sea-salt sulfates and sea spray aerosol, which likely shared similar volatile fractions composed of sulfuric acid and a non-hygroscopic organic component.

scholarly journals Linking variations in sea spray aerosol particle hygroscopicity to composition during two microcosm experiments

2016 ◽  
Vol 16 (14) ◽  
pp. 9003-9018 ◽  
Author(s):  
Sara D. Forestieri ◽  
Gavin C. Cornwell ◽  
Taylor M. Helgestad ◽  
Kathryn A. Moore ◽  
Christopher Lee ◽  
...  
Keyword(s):  
Organic Matter ◽  
Light Scattering ◽  
Time Lag ◽  
Sea Salt ◽  
Sea Spray ◽  
Phytoplankton Blooms ◽  
Chl A ◽  
Volume Fractions ◽  
Sea Spray Aerosol ◽  
Indoor And Outdoor

Abstract. The extent to which water uptake influences the light scattering ability of marine sea spray aerosol (SSA) particles depends critically on SSA chemical composition. The organic fraction of SSA can increase during phytoplankton blooms, decreasing the salt content and therefore the hygroscopicity of the particles. In this study, subsaturated hygroscopic growth factors at 85 % relative humidity (GF(85 %)) of predominately submicron SSA particles were quantified during two induced phytoplankton blooms in marine aerosol reference tanks (MARTs). One MART was illuminated with fluorescent lights and the other was illuminated with sunlight, referred to as the "indoor" and "outdoor" MARTs, respectively. Optically weighted GF(85 %) values for SSA particles were derived from measurements of light scattering and particle size distributions. The mean optically weighted SSA diameters were 530 and 570 nm for the indoor and outdoor MARTs, respectively. The GF(85 %) measurements were made concurrently with online particle composition measurements, including bulk composition (using an Aerodyne high-resolution aerosol mass spectrometer) and single particle (using an aerosol time-of-flight mass spectrometer) measurement, and a variety of water-composition measurements. During both microcosm experiments, the observed optically weighted GF(85 %) values were depressed substantially relative to pure inorganic sea salt by 5 to 15 %. There was also a time lag between GF(85 %) depression and the peak chlorophyll a (Chl a) concentrations by either 1 (indoor MART) or 3-to-6 (outdoor MART) days. The fraction of organic matter in the SSA particles generally increased after the Chl a peaked, also with a time lag, and ranged from about 0.25 to 0.5 by volume. The observed depression in the GF(85 %) values (relative to pure sea salt) is consistent with the large observed volume fractions of non-refractory organic matter (NR-OM) comprising the SSA. The GF(85 %) values exhibited a reasonable negative correlation with the SSA NR-OM volume fractions after the peak of the blooms (i.e., Chl a maxima); i.e., the GF(85 %) values generally decreased when the NR-OM volume fractions increased. The GF(85 %) vs. NR-OM volume fraction relationship was interpreted using the Zdanovskii–Stokes–Robinson (ZSR) mixing rule and used to estimate the GF(85 %) of the organic matter in the nascent SSA. The estimated pure NR-OM GF(85 %) values were 1.16 ± 0.09 and 1.23 ± 0.10 for the indoor and outdoor MARTS, respectively. These measurements demonstrate a clear relationship between SSA particle composition and the sensitivity of light scattering to variations in relative humidity. The implications of these observations to the direct climate effects of SSA particles are discussed.

scholarly journals Simulation of the chemical evolution of biomass burning organic aerosol

2019 ◽  
Vol 19 (8) ◽  
pp. 5403-5415 ◽  
Author(s):  
Georgia N. Theodoritsi ◽  
Spyros N. Pandis
Keyword(s):  
Biomass Burning ◽  
Transport Model ◽  
Organic Aerosol ◽  
Early Summer ◽  
Oxidation Products ◽  
Winter Period ◽  
Chemical Transport Model ◽  
Wood Combustion ◽  
Aerosol Mass ◽  
Photochemical Aging

Abstract. The chemical transport model PMCAMx was extended to investigate the effects of partitioning and photochemical aging of biomass burning emissions on organic aerosol (OA) concentrations. A source-resolved version of the model, PMCAMx-SR, was developed in which biomass burning emissions and their oxidation products are represented separately from the other OA components. The volatility distribution and chemical aging of biomass burning OA (BBOA) were simulated based on recent laboratory measurements. PMCAMx-SR was applied to Europe during an early summer period (1–29 May 2008) and a winter period (25 February–22 March 2009). During the early summer, the contribution of biomass burning (both primary and secondary species) to total OA levels over continental Europe was estimated to be approximately 16 %. During winter the contribution was nearly 47 %, due to both extensive residential wood combustion but also wildfires in Portugal and Spain. The intermediate volatility compounds (IVOCs) with effective saturation concentration values of 105 and 106 µg m−3 are predicted to contribute around one third of the BBOA during the summer and 15 % during the winter by forming secondary OA (SOA). The uncertain emissions of these compounds and their SOA formation potential require additional attention. Evaluation of PMCAMx-SR predictions against aerosol mass spectrometer measurements in several sites around Europe suggests reasonably good performance for OA (fractional bias less than 35 % and fractional error less than 50 %). The performance was weaker during the winter suggesting uncertainties in residential heating emissions and the simulation of the resulting BBOA in this season.

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