A New Instrument for Determining the Coarse-Mode Sea Salt Aerosol Size Distribution

AbstractSea salt aerosol(s) (SSA) play a significant role in the atmosphere through aerosol direct and indirect effects, and in atmospheric chemistry as a source of tropospheric bromine. In-situ measurements of coarse-mode SSA particles are limited because of their low concentration and relatively large sizes (dry radius, rd > 0.5 μm). With this in mind, a new, low-cost, easily usable method for sampling coarse-mode SSA particles in the marine boundary layer was developed. A SSA particle sampler that uses an impaction method was designed and built using 3D printing and Arduino microcontrollers and sensors. It exposes polycarbonate slides to ambient airflow remotely on a kite-based platform to capture coarse-mode SSA particles. Because it is a smaller version of the Giant Nucleus Impactor (GNI), designed for use on aircraft, it is named the miniature-Giant Nucleus Impactor, or “mini-GNI”. After sample collection, the same optical microscope methodology utilized by the GNI was used to analyze the wetted salt particles that impacted onto the slides. In this proof-of-concept study, multiple mini-GNIs were attached serially to a kite string, allowing for sampling at multiple altitudes simultaneously. The robustness of the results from this new instrument and methodology for sampling at ambient RH (~ 75 %) the SSA particle size distribution with rd > 3.3 μ m are compared with a similar study. We find that the SSA particle number concentration decreases weakly with altitude and shows no correlation to instantaneous U10 wind speed along the windward coastline of O‘ ahu in the Hawaiian Islands.

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Consistent simulation of bromine chemistry from the marine boundary layer to the stratosphere – Part 1: Model description, sea salt aerosols and pH

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-5899-2008 ◽

2008 ◽

Vol 8 (19) ◽

pp. 5899-5917 ◽

Cited By ~ 24

Author(s):

A. Kerkweg ◽

P. Jöckel ◽

A. Pozzer ◽

H. Tost ◽

R. Sander ◽

...

Keyword(s):

Size Distribution ◽

Atmospheric Chemistry ◽

General Circulation ◽

Circulation Model ◽

Reaction Rates ◽

Sea Salt ◽

Aerosol Size Distribution ◽

Model Description ◽

Aerosol Chemistry ◽

Coarse Mode

Abstract. This is the first article of a series presenting a detailed analysis of bromine chemistry simulated with the atmospheric chemistry general circulation model ECHAM5/MESSy. Release from sea salt is an important bromine source, hence the model explicitly calculates aerosol chemistry and phase partitioning for coarse mode aerosol particles. Many processes including chemical reaction rates are influenced by the particle size distribution, and aerosol associated water strongly affects the aerosol pH. Knowledge of the aerosol pH is important as it determines the aerosol chemistry, e.g., the efficiency of sulphur oxidation and bromine release. Here, we focus on the simulated sea salt aerosol size distribution and the coarse mode aerosol pH. A comparison with available field data shows that the simulated aerosol distributions agree reasonably well within the range of measurements. In spite of the small number of aerosol pH measurements and the uncertainty in its experimental determination, the simulated aerosol pH compares well with the observations. The aerosol pH ranges from alkaline aerosol in areas of strong production down to pH-values of 1 over regions of medium sea salt production and high levels of gas phase acids, mostly polluted regions over the oceans in the Northern Hemisphere.

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Consistent simulation of bromine chemistry from the marine boundary layer to the stratosphere, Part I: model description, sea salt aerosols and pH

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-7217-2008 ◽

2008 ◽

Vol 8 (2) ◽

pp. 7217-7262 ◽

Cited By ~ 1

Author(s):

A. Kerkweg ◽

P. Jöckel ◽

A. Pozzer ◽

H. Tost ◽

R. Sander ◽

...

Keyword(s):

Size Distribution ◽

Atmospheric Chemistry ◽

General Circulation ◽

Circulation Model ◽

Reaction Rates ◽

Sea Salt ◽

Aerosol Size Distribution ◽

Model Description ◽

Aerosol Chemistry ◽

Coarse Mode

Abstract. This is the first article of a series presenting a detailed analysis of bromine chemistry simulated with the atmospheric chemistry general circulation model ECHAM5/MESSy. Release from sea salt is an important bromine source, hence the model explicitly calculates aerosol chemistry and phase partitioning for coarse mode aerosol particles. Many processes including chemical reaction rates are influenced by the particle size distribution, and aerosol associated water strongly affects the aerosol pH. Knowledge of the aerosol pH is important as it determines the aerosol chemistry, e.g., the efficiency of sulphur oxidation and bromine release. Here, we focus on the simulated sea salt aerosol size distribution and the coarse mode aerosol pH. A comparison with available field data shows that the simulated aerosol distributions agree reasonably well within the range of measurements. In spite of the small number of aerosol pH measurements and the uncertainty in its experimental determination, the simulated aerosol pH compares well with the observations. The aerosol pH ranges from alkaline aerosol in areas of strong production down to pH values of 1 over regions of medium sea salt production and high levels of gas phase acids, mostly polluted regions over the oceans in the northern hemisphere.

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Modeling sea-salt aerosol in a coupled climate and sectional microphysical model: mass, optical depth and number concentration

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-24499-2010 ◽

2010 ◽

Vol 10 (10) ◽

pp. 24499-24561 ◽

Cited By ~ 4

Author(s):

T. Fan ◽

O. B. Toon

Keyword(s):

Wind Speed ◽

Size Distribution ◽

Optical Depth ◽

Source Function ◽

Removal Rate ◽

Global Climate Model ◽

Number Concentration ◽

Sea Salt ◽

Aerosol Size Distribution ◽

Sea Salt Aerosol

Abstract. Sea-salt aerosol mass, optical depth, and number concentration over the global oceans have significant implications for aerosol direct and indirect climate effects. We modeled sea-salt aerosol in a coupled climate and sectional microphysical model, CAM/CARMA, with aerosol dynamics including sea salt emission, gravitational sedimentation, dry deposition, wet scavenging, and particle swelling. We aimed at finding an integrated sea salt source function parameterization in the global climate model to simultaneously represent mass, optical depth, and number concentration. Each of these quantities is sensitive to a different part of the aerosol size distribution, which requires a size resolved microphysical model to treat properly. The CMS source function introduced in the research, based upon several earlier source functions, reproduced measurements of mass, optical depth and number concentration as well as the size distribution better than other source function choices we tried. However, as we note, it is also important to properly set the removal rate of the particles. The source function and removal rate are coupled in producing observed abundances. We find that sea-salt mass and optical depth peak in the winter, when winds are highest. However, surprisingly, particle numbers and CCN concentrations peak in summer when rainfall is lowest. The quadratic dependence of sea salt optical depth on wind speed, observed by some, is well represented in the model. We also found good agreement with the wind speed dependency of the number concentration at the measurement location and the regional scale. The work is the basis for further investigation of the effects of sea-salt aerosol on climate and atmospheric chemistry.

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Modeling sea-salt aerosol in a coupled climate and sectional microphysical model: mass, optical depth and number concentration

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-4587-2011 ◽

2011 ◽

Vol 11 (9) ◽

pp. 4587-4610 ◽

Cited By ~ 27

Author(s):

T. Fan ◽

O. B. Toon

Keyword(s):

Wind Speed ◽

Size Distribution ◽

Optical Depth ◽

Source Function ◽

Removal Rate ◽

Global Climate Model ◽

Number Concentration ◽

Sea Salt ◽

Aerosol Size Distribution ◽

Sea Salt Aerosol

Abstract. Sea-salt aerosol mass, optical depth, and number concentration over the global oceans have significant implications for aerosol direct and indirect climate effects. We model sea-salt aerosol in a coupled climate and sectional microphysical model, CAM/CARMA, with aerosol dynamics including sea-salt emission, gravitational sedimentation, dry deposition, wet scavenging, and hygroscopic growth. We aim to find an integrated sea-salt source function parameterization in the global climate model to simultaneously represent mass, optical depth, and number concentration. Each of these quantities is sensitive to a different part of the aerosol size distribution, which requires a size resolved microphysical model to treat properly. The CMS source function introduced in this research, based upon several earlier source functions, reproduces measurements of mass, optical depth and number concentration as well as the size distribution better than other source function choices we tried. However, as we note, it is also important to properly set the removal rate of the particles. The source function and removal rate are coupled in producing observed abundances. We find that sea salt mass and optical depth peak in the winter, when winds are highest. However, surprisingly, particle numbers and CCN concentrations peak in summer when rainfall is lowest. The quadratic dependence of sea-salt optical depth on wind speed, observed by some, is well represented in the model. We also find good agreement with the wind speed dependency of the number concentration at the measurement location and the regional scale. The work is the basis for further investigation of the effects of sea-salt aerosol on climate and atmospheric chemistry.

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Exploring ice core sea ice proxies through process-based modelling

10.5194/egusphere-egu2020-9013 ◽

2020 ◽

Author(s):

Rachael Rhodes ◽

Xin Yang ◽

Eric Wolff

Keyword(s):

Sea Ice ◽

Atmospheric Chemistry ◽

Ice Core ◽

Ice Cores ◽

Sea Salt ◽

Atmospheric Composition ◽

The Arctic ◽

Sea Salt Aerosol ◽

Aerosol Emission ◽

The Impact

It is important to understand the magnitude and rate of past sea ice changes, as well as their timing relative to abrupt shifts in other components of Earth&#8217;s climate system. Furthermore, records of past sea ice over the last few centuries are urgently needed to assess the scale of natural (internal) variability over decadal timescales. By continuously recording past atmospheric composition, polar ice cores have the potential to document changing sea ice conditions if atmospheric chemistry is altered. &#160;Sea salt aerosol, specifically sodium (Na), and bromine enrichment (Brenr, Br/Na enriched relative to seawater ratio) are two ice core sea ice proxies suggested following this premise.Here we aim to move beyond a conceptual understanding of the controls on Na and Brenr in ice cores by using process-based modelling to test hypotheses. We present results of experiments using a 3D global chemical transport model (p-TOMCAT) that represents marine aerosol emission, transport and deposition. Critically, the complex atmospheric chemistry of bromine is also included. Three fundamental issues will be examined: 1) the partitioning of Br between gas and aerosol phases, 2) sea salt aerosol production from first-year versus multi-year sea ice, and 3) the impact of increased acidity in the atmosphere due to human activity in the Arctic.

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Laboratory measurements of the optical properties of sea salt aerosol

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-221-2009 ◽

2009 ◽

Vol 9 (1) ◽

pp. 221-230 ◽

Cited By ~ 19

Author(s):

R. Irshad ◽

R. G. Grainger ◽

D. M. Peters ◽

R. A. McPheat ◽

K. M. Smith ◽

...

Keyword(s):

Refractive Index ◽

Original Data ◽

Sea Salt ◽

Aerosol Size Distribution ◽

Refractive Indices ◽

Mixing Rules ◽

Band Model ◽

Sea Salt Aerosol ◽

Sea Salt Aerosols ◽

Almost All

Abstract. The extinction spectra of laboratory generated sea salt aerosols have been measured from 1 μm to 20 μm using a Bruker 66v/S FTIR spectrometer. Concomitant measurements include temperature, pressure, relative humidity and the aerosol size distribution. The refractive indices of the sea salt aerosol have been determined using a simple harmonic oscillator band model (Thomas et al., 2004) for aerosol with relative humidities at eight different values between 0.4% to 86%. The resulting refractive index spectra show significant discrepancies when compared to existing sea salt refractive indices calculated using volume mixing rules (Shettle and Fenn, 1979). Specifically, an additional band is found in the refractive indices of dry sea salt aerosol and the new data shows increased values of refractive index at almost all wavelengths. This implies that the volume mixing rules, currently used to calculate the refractive indices of wet sea salt aerosols, are inadequate. Furthermore, the existing data for the real and imaginary parts of the refractive indices of dry sea salt aerosol are found not to display the Kramers-Kronig relationship. This implies that the original data used for the volume mixing calculations is also inaccurate.

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Evaluation of the sectional aerosol microphysics module SALSA implementation in ECHAM5-HAM aerosol-climate model

Geoscientific Model Development ◽

10.5194/gmd-5-845-2012 ◽

2012 ◽

Vol 5 (3) ◽

pp. 845-868 ◽

Cited By ~ 42

Author(s):

T. Bergman ◽

V.-M. Kerminen ◽

H. Korhonen ◽

K. J. Lehtinen ◽

R. Makkonen ◽

...

Keyword(s):

Organic Carbon ◽

Size Distribution ◽

Black Carbon ◽

Climate Model ◽

Good Choice ◽

Sea Salt ◽

Aerosol Size Distribution ◽

Chemical Compositions ◽

Model Framework ◽

Aerosol Properties

Abstract. We present the implementation and evaluation of a sectional aerosol microphysics module SALSA within the aerosol-climate model ECHAM5-HAM. This aerosol microphysics module has been designed to be flexible and computationally efficient so that it can be implemented in regional or global scale models. The computational efficiency has been achieved by minimising the number of variables needed to describe the size and composition distribution. The aerosol size distribution is described using 10 size classes with parallel sections which can have different chemical compositions. Thus in total, the module tracks 20 size sections which cover diameters ranging from 3 nm to 10 μm and are divided into three subranges, each with an optimised selection of processes and compounds. The implementation of SALSA into ECHAM5-HAM includes the main aerosol processes in the atmosphere: emissions, removal, radiative effects, liquid and gas phase sulphate chemistry, and the aerosol microphysics. The aerosol compounds treated in the module are sulphate, organic carbon, sea salt, black carbon, and mineral dust. In its default configuration, ECHAM5-HAM treats aerosol size distribution using the modal method. In this implementation, the aerosol processes were converted to be used in a sectional model framework. The ability of the module to describe the global aerosol properties was evaluated by comparing against (1) measured continental and marine size distributions, (2) observed variability of continental number concentrations, (3) measured sulphate, organic carbon, black carbon and sea-salt mass concentrations, (4) observations of aerosol optical depth (AOD) and other aerosol optical properties from satellites and AERONET network, (5) global aerosol budgets and concentrations from previous model studies, and (6) model results using M7, which is the default aerosol microphysics module in ECHAM5-HAM. The evaluation shows that the global aerosol properties can be reproduced reasonably well using a coarse resolution of 10 sections in size space. The simulated global aerosol budgets are within the range of previous studies. Surface concentrations of sulphate and carbonaceous species have an annual mean within a factor of two of the observations. The simulated sea-salt concentrations reproduce the observations within a factor of two, apart from the Southern Ocean over which the concentrations are within a factor of five. Regionally, AOD is in a relatively good agreement with the observations (within a factor of two). At mid-latitudes the observed AOD is captured well, while at high-latitudes as well as in some polluted and dust regions the modelled AOD is significantly lower than observed. Regarding most of the investigated aerosol properties, the SALSA and the modal aerosol module M7 perform comparably well against observations. However, SALSA reproduces the observed number concentrations and the size distribution of CCN sized particles much more accurately than M7, and is therefore a good choice for aerosol-cloud interaction studies in global models. Our study also shows that when activation type nucleation in the boundary layer is included, the observed concentration of particles under 50 nm in diameter are reproduced much better compared to when only binary nucleation in the free troposphere is assumed.

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Sea salt emission, transportation and influence on nitrate simulation: a case study in Europe

10.5194/acp-2016-309 ◽

2016 ◽

Cited By ~ 1

Author(s):

Ying Chen ◽

Yafang Cheng ◽

Nan Ma ◽

Ralf Wolke ◽

Stephan Nordmann ◽

...

Keyword(s):

Surface Wind ◽

Global Scale ◽

Sea Salt ◽

Wind Pattern ◽

Sea Salt Aerosol ◽

Coarse Mode ◽

Significant Difference ◽

Fine Mode ◽

Inorganic Aerosol

Abstract. Sea salt aerosol (SSA) is one of the major components of primary aerosols and has significant impact on the formation of secondary inorganic aerosol particles on a global scale. In this study, the fully online coupled WRF-Chem model was utilized to evaluate the SSA emission scheme and its influence on the nitrate simulation in a case study in Europe during September 10–20, 2013. Meteorological conditions near the surface, wind pattern, and thermal stratification structure were well reproduced by the model. Nonetheless, coarse mode (PM1–10) particle mass concentration was substantially overestimated due to the overestimation of SSA and nitrate. Compared to filter measurements at 4 EMEP stations (coastal stations: Bilthoven, Kollumerwaard and Vredepeel; inland station: Melpitz), the modeled SSA concentrations were overestimated by a factor of 8–20. We found that the overestimation was mainly caused by the overestimated SSA emission over North Sea during September 16–20. Over the coastal regions, the SSA was injected into the continental free troposphere through an “aloft bridge” (about 500 to 1000 meter above the ground), a result of the different thermodynamic properties and planetary boundary layer (PBL) structure between continental and marine regions. The injected SSA was further transported inland and mixed downward to the surface through downdraft and PBL turbulence. This process broadened the influence of SSA to a larger downwind region, for example, leading to an overestimation of SSA at Melpitz, Germany by a factor of ~20. As a result, nitrate partitioning fraction (ratio between particulate nitrate and the summation of particulate nitrate and gas-phase nitric acid) increased by about 0.2 for the coarse mode nitrate due to the overestimation of SSA at Melpitz, but no significant difference in the partitioning fraction for the fine mode nitrate. About 140 % overestimation of the coarse mode nitrate was resulted from the influence of SSA at Melpitz. On the other hand, the overestimation of SSA inhibited the nitrate formation in the fine mode by about 20 %, because of the increased consumption of precursors by coarse mode nitrate formation.

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Effect of sea-salt aerosol on tropospheric bromine chemistry

10.5194/acp-2018-1239 ◽

2018 ◽

Cited By ~ 1

Author(s):

Lei Zhu ◽

Daniel J. Jacob ◽

Sebastian D. Eastham ◽

Melissa P. Sulprizio ◽

Xuan Wang ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Marine Boundary Layer ◽

Elemental Mercury ◽

Sea Salt ◽

Heterogeneous Reactions ◽

Tropospheric Chemistry ◽

Sulfur Species ◽

Sea Salt Aerosol ◽

Volatile Organic ◽

First Time

Abstract. Bromine radicals influence global tropospheric chemistry by depleting ozone and OH, and by oxidizing elemental mercury, sulfur species, and volatile organic compounds. Observations typically indicate a 50 % depletion of sea salt aerosol (SSA) bromide relative to seawater composition, implying that SSA debromination could be the dominant global source of tropospheric bromine. However, it has been difficult to reconcile this large source with the relatively low BrO concentrations observed in the marine boundary layer (MBL). Here we present a new mechanistic description of SSA debromination in the GEOS-Chem global atmospheric chemistry model with a detailed representation of halogen (Cl, Br, and I) chemistry. We show, for the first time, observed levels of SSA debromination can be reproduced in a manner consistent with observed BrO concentrations. Bromine radical sinks from the HOBr + S(IV) heterogeneous reactions and from ocean emission of acetaldehyde are found to be critical in moderating tropospheric BrO levels. The resulting HBr is rapidly taken up by SSA and also deposited. We find that the source of bromine radicals is mostly from SSA in the MBL, but from organobromines in the free troposphere. Simulated BrO in the MBL is generally much higher in winter than in summer due to a combination of greater SSA emission and weaker radiation. Outstanding issues are the model underestimate of free tropospheric BrO, driven by the HOBr + S(IV) reactions, and uncertainty regarding HBr uptake by SSA.

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