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

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 &amp;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 &amp;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.

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

2014 ◽  
Vol 14 (10) ◽  
pp. 5057-5072 ◽  
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.

scholarly journals Ice nucleating particles at a coastal marine boundary layer site: correlations with aerosol type and meteorological conditions

2015 ◽  
Vol 15 (12) ◽  
pp. 16273-16323 ◽  
Author(s):  
R. H. Mason ◽  
M. Si ◽  
J. Li ◽  
C. Chou ◽  
R. Dickie ◽  
...  
Keyword(s):  
Size Distribution ◽  
Marine Boundary Layer ◽  
Aerosol Particles ◽  
Meteorological Conditions ◽  
Marine Aerosols ◽  
Coastal Site ◽  
Carbon Particles ◽  
Biological Particles ◽  
Ice Nuclei ◽  
Coastal Marine

Abstract. Information on what aerosol particle types are the major sources of ice nucleating particles (INPs) in the atmosphere is needed for climate predictions. To determine which aerosol particles are the major sources of immersion-mode INPs at a coastal site in Western Canada, we investigated correlations between INP number concentrations and both concentrations of different atmospheric particles and meteorological conditions. We show that INP number concentrations are strongly correlated with the number concentrations of fluorescent bioparticles between −15 and −25 °C, and that the size distribution of INPs is most consistent with the size distribution of fluorescent bioparticles. We conclude that biological particles were likely the major source of ice nuclei at freezing temperatures between −15 and −25 °C at this site for the time period studied. At −30 °C, INP number concentrations are also well correlated with number concentrations of the total aerosol particles ≥ 0.5 μm, suggesting that non-biological particles may have an important contribution to the population of INPs active at this temperature. As we found that black carbon particles were unlikely to be a major source of ice nuclei during this study, these non-biological INPs may include mineral dust. Furthermore, correlations involving tracers of marine aerosols and marine biological activity indicate that the majority of INPs measured at the coastal site likely originated from terrestrial rather than marine sources. Finally, six existing empirical parameterizations of ice nucleation were tested to determine if they accurately predict the measured INP number concentrations. We found that none of the parameterizations selected are capable of predicting INP number concentrations with high accuracy over the entire temperature range investigated.

scholarly journals Mass Extinction Efficiency Approximation for Polydispersed Aerosol Using Harmonic Mean-Type Approximation

2020 ◽  
Vol 10 (23) ◽  
pp. 8637
Author(s):  
Junshik Um ◽  
Seonghyeon Jang ◽  
Young Jun Yoon ◽  
Seoung Soo Lee ◽  
Ji Yi Lee ◽  
...  
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Extinction Coefficient ◽  
Mass Extinction ◽  
Aerosol Particles ◽  
Size Distributions ◽  
Extinction Efficiency ◽  
Type Approximation ◽  
Aerosol Mass ◽  
Mass Extinction Efficiency

Among many parameters characterizing atmospheric aerosols, aerosol mass extinction efficiency (MEE) is important for understanding the optical properties of aerosols. MEE is expressed as a function of the refractive indices (i.e., composition) and size distributions of aerosol particles. Aerosol MEE is often considered as a size-independent constant that depends only on the chemical composition of aerosol particles. The famous Malm’s reconstruction equation and subsequent revised methods express the extinction coefficient as a function of aerosol mass concentration and MEE. However, the used constant MEE does not take into account the effect of the size distribution of polydispersed chemical composition. Thus, a simplified expression of size-dependent MEE is required for accurate and conventional calculations of the aerosol extinction coefficient and also other optical properties. In this study, a simple parameterization of MEE of polydispersed aerosol particles was developed. The geometric volume–mean diameters of up to 10 µm with lognormal size distributions and varying geometric standard deviations were used to represent the sizes of various aerosol particles (i.e., ammonium sulfate and nitrate, elemental carbon, and sea salt). Integrating representations of separate small mode and large mode particles using a harmonic mean-type approximation generated the flexible and convenient parameterizations of MEE that can be readily used to process in situ observations and adopted in large-scale numerical models. The calculated MEE and the simple forcing efficiency using the method developed in this study showed high correlations with those calculated using the Mie theory without losing accuracy.

scholarly journals Cloud Processing of Aerosol Particles in Marine Stratocumulus Clouds

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 520 ◽  
Author(s):  
Andrea I. Flossmann ◽  
Wolfram Wobrock
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Numerical Study ◽  
Spatial Scales ◽  
Aerosol Particles ◽  
Cloud Microphysics ◽  
Marine Stratocumulus ◽  
Boundary Layer Clouds ◽  
Cloud Processing ◽  
Stratocumulus Clouds

Cloud processing of aerosol particles is an important process and is, for example, thought to be responsible for the so-called “Hoppel-minimum” in the marine aerosol particle distribution or contribute to the cell organization of marine boundary layer clouds. A numerical study of the temporal and spatial scales of the processing of aerosol particles by typical marine stratocumulus clouds is presented. The dynamical framework is inspired by observations during the VOCALS (Variability of the American Monsoon System Ocean-Cloud-Atmosphere-Land Study) Regional Experiment in the Southeast Pacific. The 3-D mesoscale model version of DESCAM (Detailed Scavenging Model) follows cloud microphysics of the stratocumulus deck in a bin-resolved manner and has been extended to keep track of cloud-processed particles in addition to non-processed aerosol particles in the air and inside the cloud drops. The simulation follows the evolution of the processing of aerosol particles by the cloud. It is found that within one hour almost all boundary layer aerosol particles have passed through at least one cloud cycle. However, as the in-cloud residence times of the particles in the considered case are only on the order of minutes, the aerosol particles remain essentially unchanged. Our findings suggest that in order to produce noticeable microphysical and dynamical effects in the marine boundary layer clouds, cloud processing needs to continue for extended periods of time, exceeding largely the time period considered in the present study. A second model study is dedicated to the interaction of ship track particles with marine boundary layer clouds. The model simulates quite satisfactorily the incorporation of the ship plume particles into the cloud. The observed time and spatial scales and a possible Twomey effect were reproduced.

scholarly journals Depositional ice nucleation onto hydrated NaCl particles: a new mechanism for ice formation in the troposphere

2011 ◽  
Vol 11 (8) ◽  
pp. 23139-23167 ◽  
Author(s):  
M. E. Wise ◽  
K. J. Baustian ◽  
T. Koop ◽  
M. A. Freedman ◽  
E. J. Jensen ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Aerosol Particles ◽  
Ice Nucleation ◽  
Sea Salt ◽  
Ice Formation ◽  
Radiation Balance ◽  
Atmospheric Conditions ◽  
Hydrated Form ◽  
Sea Salt Aerosol ◽  
Ice Nuclei

Abstract. Sea-salt aerosol particles (SSA) are ubiquitous in the marine boundary layer and over coastal areas. Therefore SSA have ability to directly and indirectly affect the Earth's radiation balance. The influence SSA have on climate is related to their water uptake and ice nucleation characteristics. In this study, optical microscopy coupled with Raman spectroscopy was used to detect the formation of an NaCl hydrate that could form under atmospheric conditions. NaCl(s) particles deliquesced at the well established value of 75.7 ± 2.5 % RH. NaCl(aq) particles effloresced to a mixture of hydrated and non-hydrated particles at temperatures between 236 and 252 K. The aqueous particles effloresced into the non-hydrated form at temperatures warmer than 252 K. At temperatures colder than 236 K all particles effloresced into the hydrated form. The deliquescence relative humidities (DRH) of hydrated NaCl(s) particles ranged from 76.6 to 93.2 % RH. Based on the measured DRH and efflorescence relative humidities (ERH), we estimate crystalline NaCl particles could be in the hydrated form 40–80 % of the time in the troposphere. Additionally, the ice nucleating abilities of NaCl(s) and hydrated NaCl(s) were determined at temperatures ranging from 221 to 238 K. NaCl(s) particles depositionally nucleated ice at an average Sice value of 1.11 ± 0.07. Hydrated NaCl(s) particles depositionally nucleated ice at an average Sice value of 1.02 ± 0.04. When a mixture of hydrated and anhydrous NaCl(s) particles was present in the same sample, ice preferentially nucleated on the hydrated particles 100 % of the time. While both types of particles are efficient ice nuclei, hydrated NaCl(s) particles are better ice nuclei than NaCl(s) particles.

scholarly journals Closure study between chemical composition and hygroscopic growth of aerosol particles during TORCH2

2007 ◽  
Vol 7 (24) ◽  
pp. 6131-6144 ◽  
Author(s):  
M. Gysel ◽  
J. Crosier ◽  
D. O. Topping ◽  
J. D. Whitehead ◽  
K. N. Bower ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Aerosol Particles ◽  
Residence Times ◽  
Hygroscopic Growth ◽  
Data Set ◽  
Composition Data ◽  
The North ◽  
Aerosol Mass ◽  
Hygroscopic Properties ◽  
Evaporation Losses

Abstract. Measurements of aerosol properties were made in aged polluted and clean background air masses encountered at the North Norfolk (UK) coastline as part of the TORCH2 field campaign in May 2004. Hygroscopic growth factors (GF) at 90% relative humidity (RH) for D0=27–217 nm particles and size-resolved chemical composition were simultaneously measured using a Hygroscopicity Tandem Differential Mobility Analyser (HTDMA) and an Aerodyne aerosol mass spectrometer (Q-AMS), respectively. Both hygroscopic properties and chemical composition showed pronounced variability in time and with particles size. With this data set we could demonstrate that the Zdanovskii-Stokes-Robinson (ZSR) mixing rule combined with chemical composition data from the AMS makes accurate quantitative predictions of the mean GF of mixed atmospheric aerosol particles possible. In doing so it is crucial that chemical composition data are acquired with high resolution in both particle size and time, at least matching the actual variability of particle properties. The closure results indicate an ensemble GF of the organic fraction of ~1.20±0.10 at 90% water activity. Thus the organics contribute somewhat to hygroscopic growth, particularly at small sizes, however the inorganic salts still dominate. Furthermore it has been found that most likely substantial evaporation losses of NH4NO3 occurred within the HTDMA instrument, exacerbated by a long residence time of ~1 min. Such an artefact is in agreement with our laboratory experiments and literature data for pure NH4NO3, both showing similar evaporation losses within HTDMAs with residence times of ~1 min. Short residence times and low temperatures are hence recommended for HTDMAs in order to minimise such evaporation artefacts.

Sign in / Sign up

Export Citation Format

Share Document