Primary marine aerosol‐cloud interactions off the coast of California

Modini, Robin L.; Frossard, A. A.; Ahlm, Lars; Russell, Lynn M.; Corrigan, C.; Roberts, Greg; Hawkins, Lisa; Schroder, Jason C.; Bertram, Allan K.; Zhao, Rongqin; Lee, Alex K. Y.; Abbatt, Jonathan P. D.; Lin, J. J.; Nenes, Athanasios; Wang, Zhaohui; Wonaschütz, Anna; Sorooshian, Armin; Noone, Kevin J.; Jonsson, Haflidi H.; Seinfeld, John H.; Toom-Sauntry, D.; Macdonald, A. M.; Leaitch, W. R.

doi:10.1002/2014jd022963

Cited by 101 publications

(172 citation statements)

References 92 publications

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“…Fitting three different modes to the NSDs shown in Fig. 1 reveals that particles in the third mode contribute ≈ 90 % of the total particulate mass but only 4 to 10 % of N total and up to 15 % of N CCN (i.e., when omitting the Aitken mode), comparable to what was found in earlier studies (Bates et al, 1998;Modini et al, 2015).…”

Section: Particle Number Size Distributionssupporting

confidence: 84%

“…The third mode that was visible in the NSDs measured on ACTOS can be attributed to particles originating from sea spray, in accordance with previous research (e.g., Bates et al, 1998;Modini et al, 2015). Fitting three different modes to the NSDs shown in Fig.…”

Section: Particle Number Size Distributionssupporting

confidence: 74%

“…Ammonium sulfate was reported as the main component of aerosol particles with diameters below 400 nm for marine aerosol sampled in the Caribbean by Peter et al (2008), while larger particles were found to mainly consist of sea salt. These results are consistent with those of Modini et al (2015), who state that the largest contribution to CCN originates from particles in the accumulation mode centered at 100 to 200 nm, of which non-sea-salt sulfate was the controlling chemical component. Allan et al (2008) examined aerosol particles on Puerto Rico, and air masses arriving from the east-northeast were found to be mostly free of anthropogenic influences.…”

supporting

confidence: 82%

“…During a phase of high wind speeds of 16 m s −1 , these particles from sea spray contributed on average 16 to 28 % of all CCN at 0.3 % supersaturation, while at lower wind speeds of 12 m s −1 , this fraction decreased to 5 to 10 %. Modini et al (2015) concluded that under clean marine conditions, when the ocean surface is relatively calm, particles from sea spray contribute very little to marine CCN number concentrations. Comparable results were also obtained based on modeling: Glantz et al (2004) retrieved steep vertical gradients in the sea salt mass concentrations over the Atlantic and suggested that sea salt particles do not significantly contribute to CCN.…”

mentioning

confidence: 99%

“…Bates et al (1998), participating in the same Southern Ocean ship cruise mentioned before, describe the presence of sea salt particles in a coarse-particle mode, saying that they might dominate the mass size distribution but only contribute little to number concentrations. More recently, Modini et al (2015) examined marine particle number size distributions also obtained onboard a ship off the coast of California, US. They applied three-modal fits and attributed the third mode, visible as a shoulder at particles sizes > 500 nm, to sea spray aerosol.…”

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confidence: 99%

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Aerosol arriving on the Caribbean island of Barbados: physical properties and origin

et al. 2016

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Abstract. The marine aerosol arriving at Barbados (Ragged Point) was characterized during two 3-week long measurement periods in November 2010 and April 2011, in the context of the measurement campaign CARRIBA (Cloud, Aerosol, Radiation and tuRbulence in the trade wInd regime over BArbados). Through a comparison between groundbased and airborne measurements it was shown that the former are representative of the marine boundary layer at least up to cloud base. In general, total particle number concentrations (N total ) ranged from as low as 100 up to 800 cm −3 , while number concentrations for cloud condensation nuclei (N CCN ) at a supersaturation of 0.26 % ranged from some 10 to 600 cm −3 . N total and N CCN depended on the air mass origin. Three distinct types of air masses were found. One type showed elevated values for both N total and N CCN and could be attributed to long-range transport from Africa, by which biomass burning particles from the Sahel region and/or mineral dust particles from the Sahara were advected. The second and third type both had values for N CCN below 200 cm −3 and a clear minimum in the particle number size distribution (NSD) around 70 to 80 nm (Hoppel minimum). While for one of these two types the accumulation mode was dominating (albeit less so than for air masses advected from Africa), the Aitken mode dominated the other and contributed more than 50 % of all particles. These Aitken mode particles likely were formed by new particle formation no more than 3 days prior to the measurements. Hygroscopicity of particles in the CCN size range was determined from CCN measurements to be κ = 0.66 on average, which suggests that these particles contain mainly sulfate and do not show a strong influence from organic material, which might generally be the case for the months during which measurements were made. The average κ could be used to derive N CCN from measured number size distributions, showing that this is a valid approach to obtain N CCN . Although the total particulate mass sampled on filters was found to be dominated by Na + and Cl − , this was found to be contributed by a small number of large particles (> 500 nm, mostly even in the super-micron size range). Based on a three-modal fit, a sea spray mode observed in the NSDs was found to contribute 90 % to the total particulate mass but only 4 to 10 % to N total and up to 15 % to N CCN . This is in accordance with finding no correlation between N total and wind speed.

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Section: Particle Number Size Distributionssupporting

confidence: 84%

Section: Particle Number Size Distributionssupporting

confidence: 74%

supporting

confidence: 82%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Aerosol arriving on the Caribbean island of Barbados: physical properties and origin

et al. 2016

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Meteorological and aerosol effects on marine cloud microphysical properties

et al. 2016

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Meteorology and microphysics affect cloud formation, cloud droplet distributions, and shortwave reflectance. The Eastern Pacific Emitted Aerosol Cloud Experiment and the Stratocumulus Observations of Los‐Angeles Emissions Derived Aerosol‐Droplets studies provided measurements in six case studies of cloud thermodynamic properties, initial particle number distribution and composition, and cloud drop distribution. In this study, we use simulations from a chemical and microphysical aerosol‐cloud parcel (ACP) model with explicit kinetic drop activation to reproduce observed cloud droplet distributions of the case studies. Four cases had subadiabatic lapse rates, resulting in fewer activated droplets, lower liquid water content, and higher cloud base height than an adiabatic lapse rate. A weighted ensemble of simulations that reflect measured variation in updraft velocity and cloud base height was used to reproduce observed droplet distributions. Simulations show that organic hygroscopicity in internally mixed cases causes small effects on cloud reflectivity (CR) (<0.01), except for cargo ship and smoke plumes, which increased CR by 0.02 and 0.07, respectively, owing to their high organic mass fraction. Organic hygroscopicity had larger effects on droplet concentrations for cases with higher aerosol concentrations near the critical diameter (namely, polluted cases with a modal peak near 0.1 µm). Differences in simulated droplet spectral widths (k) caused larger differences in CR than organic hygroscopicity in cases with organic mass fractions of 60% or less for the cases shown. Finally, simulations from a numerical parameterization of cloud droplet activation suitable for general circulation models compared well with the ACP model, except under high organic mass fraction.

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Ambient observations of hygroscopic growth factor and f(RH) below 1: Case studies from surface and airborne measurements

et al. 2016

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This study reports a detailed set of ambient observations of optical/physical shrinking of particles from exposure to water vapor with consistency across different instruments and regions. Data have been utilized from (i) a shipboard humidified tandem differential mobility analyzer during the Eastern Pacific Emitted Aerosol Cloud Experiment in 2011, (ii) multiple instruments on the NASA DC‐8 research aircraft during the Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys in 2013, and (iii) the Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe during ambient measurements in Tucson, Arizona, during summer 2014 and winter 2015. Hygroscopic growth factor (ratio of humidified‐to‐dry diameter, GF = Dp,wet/Dp,dry) and f(RH) (ratio of humidified‐to‐dry scattering coefficients) values below 1 were observed across the range of relative humidity (RH) investigated (75–95%). A commonality of observations of GF and f(RH) below 1 in these experiments was the presence of particles enriched with carbonaceous matter, especially from biomass burning. Evidence of externally mixed aerosol, and thus multiple GFs with at least one GF < 1, was observed concurrently with f(RH) < 1 during smoke periods. Possible mechanisms responsible for observed shrinkage are discussed and include particle restructuring, volatilization effects, and refractive index modifications due to aqueous processing resulting in optical size modification. To further investigate ambient observations of GFs and f(RH) values less than 1, it is recommended to add an optional prehumidification bypass module to hygroscopicity instruments, to preemptively collapse particles prior to controlled RH measurements.

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Primary marine aerosol‐cloud interactions off the coast of California

Cited by 101 publications

References 92 publications

Aerosol arriving on the Caribbean island of Barbados: physical properties and origin

Aerosol arriving on the Caribbean island of Barbados: physical properties and origin

Meteorological and aerosol effects on marine cloud microphysical properties

Ambient observations of hygroscopic growth factor and f(RH) below 1: Case studies from surface and airborne measurements

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