Tropospheric aerosol microphysics simulation with assimilated meteorology: model description and intermodel comparison

Abstract. We implement the TwO-Moment Aerosol Sectional (TOMAS) microphysics module into GEOS-CHEM, a CTM driven by assimilated meteorology. TOMAS has 30 size sections covering 0.01–10 μm diameter with conservation equations for both aerosol mass and number. The implementation enables GEOS-CHEM to simulate aerosol microphysics, size distributions, mass and number concentrations. The model system is developed for sulfate and sea-salt aerosols, a year-long simulation has been performed, and results are compared to observations. Additionally model intercomparison was carried out involving global models with sectional microphysics: GISS GCM-II' and GLOMAP. Comparison with marine boundary layer observations of CN10 and CCN(0.2%) shows that all models perform well with average errors of 30–50%. However, all models underpredict CN10 by up to 42% between 15° S and 45° S while overpredicting CN10 up to 52% between 45° N and 60° N, which could be due to the sea-salt emission parameterization and the assumed size distribution of primary sulfate emission, in each case respectively. Model intercomparison at the surface shows that GISS GCM-II' and GLOMAP, each compared against GEOS-CHEM, both predict 40% higher CN10 and predict 20% and 30% higher CCN(0.2%) on average, respectively. Major discrepancies are due to different emission inventories and transport. Budget comparison shows GEOS-CHEM predicts the lowest global CCN(0.2%) due to microphysical growth being a factor of 2 lower than other models because of lower SO2 availability. These findings stress the need for accurate meteorological inputs, updated emission inventories, and realistic clouds and oxidant fields when evaluating global aerosol microphysics models.

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Tropospheric aerosol microphysics simulation with assimilated meteorology: model description and intermodel comparison

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-14369-2007 ◽

2007 ◽

Vol 7 (5) ◽

pp. 14369-14411 ◽

Cited By ~ 2

Author(s):

W. Trivitayanurak ◽

P. J. Adams ◽

D. V. Spracklen ◽

K. S. Carslaw

Keyword(s):

Marine Boundary Layer ◽

Model System ◽

Sea Salt ◽

Model Description ◽

Emission Inventories ◽

Size Distributions ◽

Model Intercomparison ◽

Sea Salt Aerosols ◽

Aerosol Mass ◽

Tropospheric Aerosol

Abstract. We implement the TwO-Moment Aerosol Sectional (TOMAS) microphysics module into GEOS-CHEM, a CTM driven by assimilated meteorology. TOMAS has 30 size sections covering 0.01–10 μm diameter with conservation equations for both aerosol mass and number. The implementation enables GEOS-CHEM to simulate aerosol microphysics, size distributions, mass and number concentrations. The model system is developed for sulfate and sea-salt aerosols, a year-long simulation has been performed, and results are compared to observations. Additionally model intercomparison was carried out involving global models with sectional microphysics: GISS GCM-II' and GLOMAP. Comparison with marine boundary layer observations of CN and CCN(0.2%) shows that all models perform well with average errors of 30–50%. However, all models underpredict CN by up to 42% between 15° S and 45° S while overpredicting CN up to 52% between 45° N and 60° N, which could be due to the sea-salt emission parameterization and the assumed size distribution of primary sulfate emission, in each case respectively. Model intercomparison at the surface shows that GISS GCM-II' and GLOMAP, each compared against GEOS-CHEM, both predict 40% higher CN and predict 20% and 30% higher CCN(0.2%) on average, respectively. Major discrepancies are due to different emission inventories and transport. Budget comparison shows GEOS-CHEM predicts the lowest global CCN(0.2%) due to microphysical growth being a factor of 2 lower than other models because of lower SO2 availability. These findings stress the need for accurate meteorological inputs and updated emission inventories when evaluating global aerosol microphysics models.

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Does the POA-SOA split matter for global CCN formation?

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-10561-2013 ◽

2013 ◽

Vol 13 (4) ◽

pp. 10561-10601 ◽

Cited By ~ 2

Author(s):

W. Trivitayanurak ◽

P. J. Adams

Keyword(s):

Chemical Composition ◽

Climate Modeling ◽

Sea Salt ◽

Size Distributions ◽

Carbonaceous Aerosols ◽

Annual Average ◽

Model Driven ◽

Sea Salt Aerosols ◽

Model Layer

Abstract. A model of carbonaceous aerosols has been implemented into the TwO-Moment Aerosol Sectional (TOMAS) microphysics module in the GEOS-Chem CTM, a model driven by assimilated meteorology. Inclusion of carbonaceous emissions alongside pre-existing treatments of sulfate and sea-salt aerosols increases the number of emitted primary aerosol particles by a factor of 2.5 and raises annual-average global CCN(0.2%) concentrations by a factor of two. Compared to the prior model without carbonaceous aerosols, this development improves the model prediction of CN10 number concentrations significantly from −45 to −7% bias when compared to long-term observations. However, similar to other OC/EC models, the model underpredicts OC and EC mass concentrations by a factor of 2–5 when compared to EMEP observations. Because primary OA and secondary OA affect aerosol number size distributions differently, we assess the sensitivity of CCN production, for a fixed source of OA mass, to the assumed POA-SOA split in the model. For a fixed OA budget, we found that CCN(0.2%) decreases nearly everywhere as the model changes from a world dominated by POA emissions to one dominated by SOA condensation. POA is about twice as effective per unit mass at CCN production compared to SOA. Changing from a 100% POA scenario to a 100% SOA scenario, CCN(0.2%) concentrations in the lowest model layer decrease by about 20%. In any scenario, carbonaceous aerosols contribute significantly to global CCN. The SOA-POA split has a significant effect on global CCN and the microphysical implications of POA emissions versus SOA condensation appear to be at least as important as differences in chemical composition as expressed by the hygroscopicity of OA. These findings stress the need to better understand carbonaceous aerosols loadings, the global SOA budget, microphysical pathways of OA formation (emissions versus condensation) as well as chemical composition to improve climate modeling.

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BrCl production in NaBr/NaCl/HNO3/O3solutions representative of sea-salt aerosols in the marine boundary layer

Geophysical Research Letters ◽

10.1029/1999gl900251 ◽

1999 ◽

Vol 26 (14) ◽

pp. 2183-2186 ◽

Cited By ~ 17

Author(s):

R. S. Disselkamp ◽

E. G. Chapman ◽

W. R. Barchet ◽

S. D. Colson ◽

C. D. Howd

Keyword(s):

Boundary Layer ◽

Marine Boundary Layer ◽

Sea Salt ◽

Sea Salt Aerosols

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Separating refractory and non-refractory particulate chloride and estimating chloride depletion by aerosol mass spectrometry in a marine environment

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-2085-2015 ◽

2015 ◽

Vol 15 (2) ◽

pp. 2085-2118 ◽

Cited By ~ 4

Author(s):

I. Nuaaman ◽

S.-M. Li ◽

K. L. Hayden ◽

T. B. Onasch ◽

P. Massoli ◽

...

Keyword(s):

Scaling Factor ◽

Sea Salt ◽

Lower Sensitivity ◽

Aerosol Composition ◽

Ambient Aerosols ◽

Sea Salt Aerosols ◽

Aerosol Mass ◽

Chloride Depletion ◽

Good Tracer ◽

Continental Outflow

Abstract. Aerosol composition and concentration measurements along the coast of California were obtained using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-AMS) onboard the research vessel Atlantis during the CalNex study in 2010. This paper focuses on the measurement of aerosol chloride using the HR-AMS that can be ambiguous in regions with significant quantities of sea salt aerosols. This ambiguity arises due to large differences in the sensitivity of the HR-AMS to refractory chloride species (i.e., NaCl) and non refractory chloride species (i.e., NH4Cl, HCl, etc.). Using the HR-AMS, the aerosol chloride signal is typically quantified using ion signals for 35Cl+, H35Cl+, 37Cl+ and H37Cl+ (HxCl&plus;). During this study, the highest aerosol chloride signal was observed during sea sweep experiments when the source of the aerosol chloride was NaCl present in artificially generated sea salt aerosols even though the HR-AMS has significantly lower sensitivity to such refractory species. Other prominent ion signals that arise from NaCl salt were also observed at m/z 22.99 for Na&plus; and m/z 57.96 for Na35Cl&plus; during both sea sweep experiments and during periods of ambient measurements. Thus, refractory NaCl contributes significantly to the HxCl&plus; signal, interfering with attempts to quantify non sea salt chloride (nssCl). It was found that during ambient aerosol measurements, the interference in the HxCl&plus; signal from sea salt chloride (ssCl) was as high as 89%, but with a study wide average of 10%. The Na35Cl&plus; ion signal was found to be a good tracer for NaCl. We outline a method to establish nssCl in the ambient aerosols by subtracting the sea salt chloride (ssCl) signal from the HxCl&plus; signal. The ssCl signal is derived from the Na35Cl&plus; ion tracer signal and the HxCl&plus; to Na35Cl&plus; ratio established from the sea sweep experiments. Ambient submicron concentrations of ssCl were also established using the Na35Cl&plus; ion tracer signal and a scaling factor determined through simultaneous measurements of submicron aerosol chloride on filters. This scaling factor accounts for the low vaporization response of the AMS heater to ssCl, although regular calibration of this response is recommended in future applications. It follows that true total particulate chloride (pCl) is the sum of nssCl and ssCl. In this study, the median levels observed for the concentrations of pCl, nssCl and ssCl were 0.052, 0.017 and 0.024 μg m−3 respectively. The average contributions of nssCl and ssCl to pCl were 48 and 52% respectively, with nssCl dominating in periods of continental outflow and ssCl dominating during other periods. Finally, we propose a method to measure percentage chloride depletion of NaCl in ambient submicron sea salt aerosols, strictly using the AMS measurements of Na&plus; and Na35Cl&plus; ion signals. The median chloride depletion in submicron aerosols in this study was found to be 78%.

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Chemical composition and sources of coastal marine aerosol particles during the 2008 VOCALS-REx campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-5057-2014 ◽

2014 ◽

Vol 14 (10) ◽

pp. 5057-5072 ◽

Cited By ~ 5

Author(s):

Y.-N. Lee ◽

S. Springston ◽

J. Jayne ◽

J. Wang ◽

J. Hubbe ◽

...

Keyword(s):

Chemical Composition ◽

Marine Boundary Layer ◽

Aerosol Particles ◽

Sea Salt ◽

Department Of Energy ◽

Cloud Processing ◽

Aerosol Mass ◽

Coastal Marine ◽

Marine Stratus ◽

Continental Origin

Abstract. The chemical composition of aerosol particles (Dp ≤ 1.5 μm) was measured over the southeast Pacific Ocean during the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-Rex) between 16 October and 15 November 2008 using the US Department of Energy (DOE) G-1 aircraft. The objective of these flights was to gain an understanding of the sources and evolution of these aerosols, and of how they interact with the marine stratus cloud layer that prevails in this region of the globe. Our measurements showed that the marine boundary layer (MBL) aerosol mass was dominated by non-sea-salt SO42−, followed by Na+, Cl−, Org (total organics), NH4+, and NO3−, in decreasing order of importance; CH3SO3− (MSA), Ca2+, and K+ rarely exceeded their limits of detection. Aerosols were strongly acidic with a NH4+ to SO42− equivalents ratio typically < 0.3. Sea-salt aerosol (SSA) particles, represented by NaCl, exhibited Cl− deficits caused by both HNO3 and H2SO4, but for the most part were externally mixed with particles, mainly SO42−. SSA contributed only a small fraction of the total accumulation mode particle number concentration. It was inferred that all aerosol species (except SSA) were of predominantly continental origin because of their strong land-to-sea concentration gradient. Comparison of relative changes in median values suggests that (1) an oceanic source of NH3 is present between 72° W and 76° W, (2) additional organic aerosols from biomass burns or biogenic precursors were emitted from coastal regions south of 31° S, with possible cloud processing, and (3) free tropospheric (FT) contributions to MBL gas and aerosol concentrations were negligible. The very low levels of CH3SO3− observed as well as the correlation between SO42− and NO3− (which is thought primarily anthropogenic) suggest a limited contribution of DMS to SO42− aerosol production during VOCALS.

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Simulating aerosol microphysics with the ECHAM/MADE GCM – Part I: Model description and comparison with observations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-5-7965-2005 ◽

2005 ◽

Vol 5 (5) ◽

pp. 7965-8026 ◽

Cited By ~ 1

Author(s):

A. Lauer ◽

J. Hendricks ◽

I. Ackermann ◽

B. Schell ◽

H. Hass ◽

...

Keyword(s):

General Circulation ◽

Particle Number ◽

Marine Boundary Layer ◽

Current Model ◽

Circulation Model ◽

General Circulation Models ◽

Model System ◽

Model Description ◽

Acid Vapor ◽

New Model

Abstract. The aerosol dynamics module MADE has been coupled to the general circulation model ECHAM4 to simulate the chemical composition, number concentration, and size distribution of the global submicrometer aerosol. The present publication describes the new model system ECHAM4/MADE and presents model results in comparison with observations. The new model is able to simulate the full life cycle of particulate matter and various gaseous precursors including emissions of primary particles and trace gases, advection, convection, diffusion, coagulation, condensation, nucleation of sulfuric acid vapor, aerosol chemistry, cloud processing, and size-dependent dry and wet deposition. Aerosol components considered are sulfate (SO4), ammonium (NH4), nitrate (NO3), black carbon (BC), particulate organic matter (POM), sea salt, mineral dust, and aerosol liquid water. The model is numerically efficient enough to allow long term simulations, which is an essential requirement for application in general circulation models. In order to evaluate the results obtained with this new model system, calculated mass concentrations, particle number concentrations, and size distributions are compared to observations. The intercomparison shows, that ECHAM4/MADE is able to reproduce the major features of the geographical patterns, seasonal cycle, and vertical distributions of the basic aerosol parameters. In particular, the model performs well under polluted continental conditions in the northern hemispheric lower and middle troposphere. However, in comparatively clean remote areas, e.g. in the upper troposphere or in the southern hemispheric marine boundary layer, the current model version tends to underestimate particle number concentrations.

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Characterization of the South Atlantic marine boundary layer aerosol using an Aerodyne Aerosol Mass Spectrometer

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-4831-2008 ◽

2008 ◽

Vol 8 (2) ◽

pp. 4831-4876 ◽

Cited By ~ 5

Author(s):

S. R. Zorn ◽

F. Drewnick ◽

M. Schott ◽

T. Hoffmann ◽

S. Borrmann

Keyword(s):

Boundary Layer ◽

Sulfuric Acid ◽

Marine Boundary Layer ◽

Methanesulfonic Acid ◽

Field Measurements ◽

Size Distributions ◽

Air Masses ◽

Aerosol Mass ◽

Mass Size ◽

Mass Concentrations

Abstract. Measurements of the submicron fraction of the atmospheric aerosol in the marine boundary layer were performed from January to March 2007 (Southern Hemisphere summer) onboard the French research vessel Marion Dufresne in the Southern Atlantic and Indian Ocean (20° S–60° S, 70° W–60° E). For chemical composition measurements an Aerodyne High-Resolution-Time-of-Flight AMS was used to measure mass concentrations and species-resolved size distributions of non-refractory aerosol components in the submicron range. Within the "standard" AMS compounds (ammonium, chloride, nitrate, sulfate, organics) "sulfate" is the dominating species in the marine boundary layer reaching concentrations between 50 ng m−3 and 3 μg m−3. Furthermore, what is seen as "sulfate" by the AMS seems to be mostly sulfuric acid. Another sulfur containing species that can ubiquitously be found in marine environments is methanesulfonic acid (MSA). Since MSA has not been directly measured before with an AMS, and is not part of the standard AMS analysis, laboratory experiments needed to be performed in order to be able to identify it within the AMS raw data and to extract mass concentrations for MSA from the field measurements. To identify characteristic air masses and their source regions backwards trajectories were used and averaged concentrations for AMS standard compounds were calculated for each air mass type. Sulfate mass size distributions were measured for these periods showing a distinct difference between oceanic air masses and those from African outflow. While the peak size in the mass distribution was roughly 250 nm in marine air masses it was shifted to 470 nm in African outflow air. Correlations between the mass concentrations of sulfate, organics and MSA were calculated which show a narrow correlation for MSA with sulfate/sulfuric acid coming from the ocean but not with continental sulfate.

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Chemical composition and sources of coastal marine aerosol particles during the 2008 VOCALS-REx campaign

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-26043-2013 ◽

2013 ◽

Vol 13 (10) ◽

pp. 26043-26115

Author(s):

Y.-N. Lee ◽

S. Springston ◽

J. Jayne ◽

J. Wang ◽

J. Hubbe ◽

...

Keyword(s):

Chemical Composition ◽

Marine Boundary Layer ◽

Aerosol Particles ◽

Sea Salt ◽

Strongly Correlated ◽

Cloud Processing ◽

Aerosol Mass ◽

Coastal Marine ◽

Marine Stratus ◽

Continental Origin

Abstract. The chemical composition of aerosol particles (Dp &leq; 1.5 μm) was measured over the southeast Pacific ocean during the VOCALS-REx experiment between 16~October and 15 November 2008 using the US DOE G-1 aircraft. The objective of these flights was to gain an understanding of the sources and evolution of these aerosols, and how they interacted with the marine stratus cloud layer that prevails in this region of the globe. Our measurements showed that the marine boundary layer (MBL) aerosol mass was dominated by non-sea-salt SO42−, followed by Na+, Cl−, Org, NH4+, and NO3−, in decreasing order of importance; CH3SO3−1 (MSA), Ca2+, and K+ rarely exceeded their limits of detection of ~0.05 and ~0.15 μg m−3 for anions and cations, respectively. The aerosols were strongly acidic as the NH4+ to SO42− equivalence ratio was typically < 0.3; this inferred acidity is corroborated by the conductivity of aqueous samples collected by the PILS. Sea-salt aerosol (SSA) particles, represented by NaCl, showed Cl− deficits caused by both HNO3 and H2SO4, and were externally mixed with SO42− particles as the AMS detected no NO3− whilst uptake of HNO3 occurred only on SSA particles. The SSA loading as a function of wind speed agreed with that calculated from published relationships, and contributed only a small fraction of the total accumulation mode particle number. Vertical distribution of MBL SSA particles (Dp &leq; ~1.5 μm) was uniform, suggesting a very limited dilution from entrainment of free tropospheric (FT) air. It was inferred that because all of the aerosol species (except SSA) exhibited a strong land-to-sea gradient, they were of continental origin. Comparison of relative changes in median values using LOWESS fits as proxies suggests that (1) an oceanic source of NH3 is present between 72° W and 76° W, and (2) additional organic aerosols from biomass burns or biogenic precursors were emitted from coastal regions south of 31° S, with possible cloud processing, and (3) FT contributions to MBL gas and aerosols were negligible. Positive Matrix Factorization analysis of organic aerosol mass spectra obtained with the AMS showed an HOA on 28 October 2008 but not on 6 November 2008 that we attribute to a more extensive cloud processing on the later date. A highly oxidized OOA factor resembling fulvic acid was found associated with anthropogenic and biogenic sources as well as long range transported biomass burn plumes in the FT air. A sulfur-containing OOA factor identified as MSA was strongly correlated with SO42−, hence anthropogenic. The very low levels of CH3SO3− observed suggest a limited contribution of DMS to SO42− aerosols production during VOCALS.

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