Investigating Primary Marine Aerosol Properties: CCN Activity of Sea Salt and Mixed Inorganic–Organic Particles

Abstract. Chemical composition and hygroscopicity closure of marine aerosol in high time resolution has not been achieved yet due to the difficulty involved in measuring the refractory sea-salt concentration in near-real time. In this study, attempts were made to achieve closure for marine aerosol based on a humidified tandem differential mobility analyser (HTDMA) and a high-resolution time-of-flight aerosol mass spectrometer (AMS) for wintertime aerosol at Mace Head, Ireland. The aerosol hygroscopicity was examined as a growth factor (GF) at 90 % relative humidity (RH). The corresponding GFs of 35, 50, 75, 110 and 165 nm particles were 1.54±0.26, 1.60±0.29, 1.66±0.31, 1.72±0.29 and 1.78±0.30 (mean ± standard deviation), respectively. Two contrasting air masses (continental and marine) were selected to study the temporal variation in hygroscopicity; the results demonstrated a clear diurnal pattern in continental air masses, whereas no diurnal pattern was found in marine air masses. In addition, wintertime aerosol was observed to be largely externally mixed in both of the contrasting air masses. Concurrent high time resolution PM1 (particulate matter <1 µm) chemical composition data from combined AMS and MAAP measurements, comprising organic matter, non-sea-salt sulfate, nitrate, ammonium, sea salt and black carbon (BC), were used to predict aerosol hygroscopicity with the Zdanovskii–Stokes–Robinson (ZSR) mixing rule. Overall, good agreement (an R2 value of 0.824 and a slope of 1.02) was found between the growth factor of 165 nm particles measured by the HTDMA (GF_HTDMA) and the growth factor derived from the AMS + MAAP bulk chemical composition (GF_AMS). Over 95 % of the estimated GF values exhibited less than a 10 % deviation for the whole dataset, and this deviation was mostly attributed to the neglected mixing state as a result of the bulk PM1 composition.

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

Atmospheric Measurement Techniques ◽

10.5194/amt-11-4361-2018 ◽

2018 ◽

Vol 11 (7) ◽

pp. 4361-4372 ◽

Cited By ~ 1

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.

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

Geoscientific Model Development Discussions ◽

10.5194/gmdd-4-3623-2011 ◽

2011 ◽

Vol 4 (4) ◽

pp. 3623-3690 ◽

Cited By ~ 6

Author(s):

T. Bergman ◽

V.-M. Kerminen ◽

H. Korhonen ◽

K. J. Lehtinen ◽

R. Makkonen ◽

...

Keyword(s):

Climate Model ◽

Global Scale ◽

Good Choice ◽

Sea Salt ◽

Aerosol Size Distribution ◽

Size Distributions ◽

Computationally Efficient ◽

Model Studies ◽

Aerosol Module ◽

Aerosol Properties

Abstract. We present the implementation and evaluation of a sectional aerosol microphysics model 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 keeping the number of variables needed to describe the size and composition distribution to the minimum. The aerosol size distribution is described using 20 size sections with 10 size sections in size space which cover diameters ranging from 3 nm to 10 μm divided to three subranges each having distinct optimised process and compound selection. The ability of the module to describe the global aerosol properties was evaluated by comparison against (1) measured continental and marine size distributions, (2) observed variability of continental modal number concentrations, (3) measured sulphate, organic carbon, black carbon and sea salt mass concentrations, (4) observations of 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 the coarse resolution of 10 size sections in size space. The simulated global aerosol budgets are within the range of previous studies. Surface concentrations of sea salt, sulphate and carbonaceous species have an annual mean within a factor of five of the observations, while the simulated sea salt concentrations reproduce the observations less accurately and show high variability. Regionally, AOD is in 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 modeled AOD is significantly lower than the observed. Regarding the most investigated aerosol properties, the performances of SALSA and the modal aerosol module M7 against observations are comparable. However, SALSA reproduces the observed number concentrations and the size distributions 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 including activation type nucleation process in the boundary layer, the modeled concentrations of particles under 50 nm in diameter are reproduced much better compared to when only binary nucleation is assumed.

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Impact of fatty acid coating on the CCN activity of sea salt particles

Tellus B ◽

10.1080/16000889.2017.1304064 ◽

2017 ◽

Vol 69 (1) ◽

pp. 1304064 ◽

Cited By ~ 20

Author(s):

Quynh T. Nguyen ◽

Kristine H. Kjær ◽

Kirsten I. Kling ◽

Thomas Boesen ◽

Merete Bilde

Keyword(s):

Fatty Acid ◽

Sea Salt ◽

Acid Coating ◽

Ccn Activity

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Determination of methanesulfonic acid and non-sea-salt sulfate in single marine aerosol particles

Environmental Science & Technology ◽

10.1021/es00179a018 ◽

1989 ◽

Vol 23 (2) ◽

pp. 236-240 ◽

Cited By ~ 34

Author(s):

Leonidas N. Kolaitis ◽

Frank J. Bruynseels ◽

Rene E. Van Grieken ◽

Meinrat O. Andreae

Keyword(s):

Aerosol Particles ◽

Methanesulfonic Acid ◽

Sea Salt ◽

Marine Aerosol

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A global off-line model of size-resolved aerosol microphysics: II. Identification of key uncertainties

Atmospheric Chemistry and Physics ◽

10.5194/acp-5-3233-2005 ◽

2005 ◽

Vol 5 (12) ◽

pp. 3233-3250 ◽

Cited By ~ 98

Author(s):

D. V. Spracklen ◽

K. J. Pringle ◽

K. S. Carslaw ◽

M. P. Chipperfield ◽

G. W. Mann

Keyword(s):

Nucleation Rate ◽

Marine Boundary Layer ◽

Cloud Condensation Nuclei ◽

Accommodation Coefficient ◽

Sulfate Aerosol ◽

Sea Salt ◽

Condensation Nuclei ◽

Microphysical Processes ◽

Global Mean ◽

Aerosol Properties

Abstract. We use the new GLOMAP model of global aerosol microphysics to investigate the sensitivity of modelled sulfate and sea salt aerosol properties to uncertainties in the driving microphysical processes and compare these uncertainties with those associated with aerosol and precursor gas emissions. Overall, we conclude that uncertainties in microphysical processes have a larger effect on global sulfate and sea salt derived condensation nuclei (CN) and cloud condensation nuclei (CCN) concentrations than uncertainties in present-day sulfur emissions. Our simulations suggest that uncertainties in predicted sulfate and sea salt CCN abundances due to poorly constrained microphysical processes are likely to be of a similar magnitude to long-term changes in sulfate and sea salt CCN due to changes in anthropogenic emissions. A microphysical treatment of the global sulfate aerosol allows the uncertainty in climate-relevant aerosol properties to be attributed to specific processes in a way that has not been possible with simpler aerosol schemes. In particular we conclude that: (1) changes in the binary H2SO4-H2O nucleation rate and condensation rate of gaseous H2SO4 cause a shift in the vertical location of the upper tropospheric CN layer by as much as 3 km, while the shape of the CN profile is essentially pre-served (2) uncertainties in the binary H2SO4-H2O nucleation rate have a relatively insignificant effect on marine boundary layer (MBL) aerosol properties; (3) emitting a fraction of anthropogenic SO2 as particulates (to represent production of sulfate particles in power plant plumes below the scale of the model grid (which is of the order of 300 km)) has the potential to change the global mean MBL sulfate-derived CN concentrations by up to 72%, and changes of up to a factor 20 can occur in polluted continental regions; (4) predicted global mean MBL sulfate and sea salt CCN concentrations change by 10 to 60% when several microphysical processes are changed within reasonable uncertainty ranges; (5) sulfate and sea salt derived CCN concentrations are particularly sensitive to primary particle emissions, with global mean MBL sulfate and sea salt CCN changing by up to 27% and local concentrations over continental regions changing by more than 100% when the percentage of anthropogenic SO2 emitted as particulates is changed from 0 to 5%; (6) large changes in sea spray flux have insignificant effects on global sulfate aerosol except when the mass accommodation coefficient of sulfuric acid on the salt particles is set unrealistically low.

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Dry versus wet marine particle optical properties: RH dependence of depolarization ratio, backscatter, and extinction from multiwavelength lidar measurements during SALTRACE

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-14199-2017 ◽

2017 ◽

Vol 17 (23) ◽

pp. 14199-14217 ◽

Cited By ~ 35

Author(s):

Moritz Haarig ◽

Albert Ansmann ◽

Josef Gasteiger ◽

Konrad Kandler ◽

Dietrich Althausen ◽

...

Keyword(s):

Sea Salt ◽

Strong Increase ◽

Aerosol Layer ◽

Marine Aerosol ◽

Depolarization Ratio ◽

Atmospheric Conditions ◽

Hygroscopic Growth ◽

Backscatter Coefficient ◽

Linear Depolarization Ratio ◽

Lidar Observations

Abstract. Triple-wavelength lidar observations of the depolarization ratio and the backscatter coefficient of marine aerosol as a function of relative humidity (RH) are presented with a 5 min time resolution. The measurements were performed at Barbados (13° N, 59° W) during the Saharan Aerosol Long-range Transport and Aerosol-Cloud interaction Experiment (SALTRACE) winter campaign in February 2014. The phase transition from spherical sea salt particles to cubic-like sea salt crystals was observed with a polarization lidar. The radiosonde and water-vapor Raman lidar observations show a drop in RH below 50 % in the marine aerosol layer simultaneously with a strong increase in particle linear depolarization ratio, which reaches values up to 0.12 ± 0.08 (at 355 nm), 0.15 ± 0.03 (at 532 nm), and 0.10 ± 0.01 (at 1064 nm). The lidar ratio (extinction-to-backscatter ratio) increased from 19 and 23 sr for spherical sea salt particles to 27 and 25 sr (at 355 and 532 nm, respectively) for cubic-like particle ensembles. Furthermore the scattering enhancement due to hygroscopic growth of the marine aerosol particles under atmospheric conditions was measured. Extinction enhancement factors from 40 to 80 % RH of 1.94 ± 0.94 at 355 nm, 3.70 ± 1.14 at 532 nm, and 5.37 ± 1.66 at 1064 nm were found. The enhanced depolarization ratios and lidar ratios were compared to modeling studies of cubic sea salt particles.

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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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Marine aerosol properties over the Southern Ocean in relation to the wintertime meteorological conditions

Atmospheric Chemistry and Physics ◽

10.5194/acp-22-119-2022 ◽

2022 ◽

Vol 22 (1) ◽

pp. 119-137

Author(s):

Manu Anna Thomas ◽

Abhay Devasthale ◽

Michael Kahnert

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Relative Humidity ◽

Southern Ocean ◽

Surface Wind ◽

Ocean Surface ◽

Meteorological Conditions ◽

Sea Salt ◽

Aerosol Backscatter ◽

Aerosol Properties

Abstract. Given the vast expanse of oceans on our planet, marine aerosols (and sea salt in particular) play an important role in the climate system via multitude of direct and indirect effects. The efficacy of their net impact, however, depends strongly on the local meteorological conditions that influence their physical, optical and chemical properties. Understanding the coupling between aerosol properties and meteorological conditions is therefore important. It has been historically difficult to statistically quantify this coupling over larger oceanic areas due to the lack of suitable observations, leading to large uncertainties in the representation of aerosol processes in climate models. Perhaps no other region shows higher uncertainties in the representation of marine aerosols and their effects than the Southern Ocean. During winter the Southern Ocean boundary layer is dominated by sea salt emissions. Here, using 10 years of austral winter period (June, July and August, 2007–2016) space-based aerosol profiling by CALIOP-CALIPSO in combination with meteorological reanalysis data, we investigated the sensitivity of marine aerosol properties over the Southern Ocean (40–65∘ S) to various meteorological parameters, such as vertical relative humidity (RH), surface wind speed and sea surface temperature (SST) in terms of joint histograms. The sensitivity study is done for the climatological conditions and for the enhanced cyclonic and anticyclonic conditions in order to understand the impact of large-scale atmospheric circulation on the aerosol properties. We find a clear demarcation in the 532 nm aerosol backscatter and extinction at RH around 60 %, irrespective of the state of the atmosphere. The backscatter and extinction increase at higher relative humidity as a function of surface wind speed. This is mainly because of the water uptake by the wind-driven sea salt aerosols at high RH near the ocean surface resulting in an increase in size, which is confirmed by the decreased depolarization for the wet aerosols. An increase in aerosol backscatter and extinction is observed during the anticyclonic conditions compared to cyclonic conditions for the higher wind speeds and relative humidity, mainly due to aerosols being confined to the boundary layer, and their proximity to the ocean surface facilitates the growth of the particles. We further find a very weak dependency of aerosol backscatter on SSTs at lower wind speeds. However, when the winds are stronger than about 12 m s−1, the backscattering coefficient generally increases with SST. When aerosol properties are investigated in terms of aerosol verticality and in relation to meteorological parameters, it is seen that the aerosol backscatter values in the free troposphere (pressure <850 hPa) are much lower than in the boundary layer, irrespective of the RH and the three weather states. This indicates that the local emissions from the ocean surface make the dominant contribution to aerosol loads over the Southern Ocean. A clear separation of particulate depolarization is observed in the free and lower troposphere, more prominent in the climatological mean and the cyclonic states. For RH > 60 %, low depolarization values are noticeable in the lower troposphere, which is an indication of the dominance of water-coated and mostly spherical sea salt particles. For RH < 60 %, there are instances when the aerosol depolarization increases in the boundary layer; this is more prominent in the mean and anticyclonic cases, which can be associated with the presence of drier aerosol particles. Based on the joint histograms investigated here, we provide third-degree polynomials to obtain aerosol extinction and backscatter as a function of wind speed and relative humidity. Additionally, backscattering coefficient is also expressed jointly in terms of wind speed and sea surface temperature. Furthermore, depolarization is expressed as a function of relative humidity. These fitting functions would be useful to test and improve the parameterizations of sea salt aerosols in the climate models. We also note some limitations of our study. For example, interpreting the verticality of aerosol properties (especially depolarization) in relation to the meteorological conditions in the free and upper troposphere (pressure <850 hPa) was challenging. Furthermore, we do not see any direct evidence of sudden crystallization (efflorescence), deliquescence or hysteresis effects of the aerosols. Observing such effects will likely require a targeted investigation of individual cases considering tracer transport, rather than the statistical sensitivity study that entails temporally and geographically averaged large data sets.

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