scholarly journals Particle-resolved simulation of aerosol size, composition, mixing state, and the associated optical and cloud condensation nuclei activation properties in an evolving urban plume

2010 ◽  
Vol 115 (D17) ◽  
Author(s):  
Rahul A. Zaveri ◽  
James C. Barnard ◽  
Richard C. Easter ◽  
Nicole Riemer ◽  
Matthew West
Keyword(s):  
Cloud Condensation Nuclei ◽  
Size Composition ◽  
Condensation Nuclei ◽  
Mixing State ◽  
Urban Plume

scholarly journals Impact of dry intrusion events on the composition and mixing state of particles during the winter Aerosol and Cloud Experiment in the Eastern North Atlantic (ACE-ENA)

2021 ◽  
Vol 21 (24) ◽  
pp. 18123-18146
Author(s):  
Jay M. Tomlin ◽  
Kevin A. Jankowski ◽  
Daniel P. Veghte ◽  
Swarup China ◽  
Peiwen Wang ◽  
...  
Keyword(s):  
Long Range ◽  
North Atlantic ◽  
Cloud Condensation Nuclei ◽  
Aerosol Size Distribution ◽  
Condensation Nuclei ◽  
Mixing State ◽  
Carbonaceous Particles ◽  
X Ray ◽  
Eastern North Atlantic ◽  
Individual Particles

Abstract. Long-range transport of continental emissions has a far-reaching influence over remote regions, resulting in substantial change in the size, morphology, and composition of the local aerosol population and cloud condensation nuclei (CCN) budget. Here, we investigate the physicochemical properties of atmospheric particles collected on board a research aircraft flown over the Azores during the winter 2018 Aerosol and Cloud Experiment in the Eastern North Atlantic (ACE-ENA) campaign. Particles were collected within the marine boundary layer (MBL) and free troposphere (FT) after long-range atmospheric transport episodes facilitated by dry intrusion (DI) events. Chemical and physical properties of individual particles were investigated using complementary capabilities of computer-controlled scanning electron microscopy and X-ray spectromicroscopy to probe particle external and internal mixing state characteristics. Furthermore, real-time measurements of aerosol size distribution, cloud condensation nuclei (CCN) concentration, and back-trajectory calculations were utilized to help bring into context the findings from offline spectromicroscopy analysis. While carbonaceous particles were found to be the dominant particle type in the region, changes in the percent contribution of organics across the particle population (i.e., external mixing) shifted from 68 % to 43 % in the MBL and from 92 % to 46 % in FT samples during DI events. This change in carbonaceous contribution is counterbalanced by the increase in inorganics from 32 % to 57 % in the MBL and 8 % to 55 % in FT. The quantification of the organic volume fraction (OVF) of individual particles derived from X-ray spectromicroscopy, which relates to the multi-component internal composition of individual particles, showed a factor of 2.06 ± 0.16 and 1.11 ± 0.04 increase in the MBL and FT, respectively, among DI samples. We show that supplying particle OVF into the κ-Köhler equation can be used as a good approximation of field-measured in situ CCN concentrations. We also report changes in the κ values in the MBL from κMBL, non-DI=0.48 to κMBL, DI=0.41, while changes in the FT result in κFT, non-DI=0.36 to κFT, DI=0.33, which is consistent with enhancements in OVF followed by the DI episodes. Our observations suggest that entrainment of particles from long-range continental sources alters the mixing state population and CCN properties of aerosol in the region. The work presented here provides field observation data that can inform atmospheric models that simulate sources and particle composition in the eastern North Atlantic.

scholarly journals Size-resolved cloud condensation nuclei (CCN) activity and closure analysis at the HKUST Supersite in Hong Kong

2014 ◽  
Vol 14 (18) ◽  
pp. 10267-10282 ◽  
Author(s):  
J. W. Meng ◽  
M. C. Yeung ◽  
Y. J. Li ◽  
B. Y. L. Lee ◽  
C. K. Chan
Keyword(s):  
Particle Size ◽  
Hong Kong ◽  
Atmospheric Aerosols ◽  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
Volume Ratio ◽  
Condensation Nuclei ◽  
Mixing State ◽  
Scanning Mobility Particle Sizer ◽  
The Mean

Abstract. The cloud condensation nuclei (CCN) properties of atmospheric aerosols were measured on 1–30 May 2011 at the HKUST (Hong Kong University of Science and Technology) Supersite, a coastal site in Hong Kong. Size-resolved CCN activation curves, the ratio of number concentration of CCN (NCCN) to aerosol concentration (NCN) as a function of particle size, were obtained at supersaturation (SS) = 0.15, 0.35, 0.50, and 0.70% using a DMT (Droplet Measurement Technologies) CCN counter (CCNc) and a TSI scanning mobility particle sizer (SMPS). The mean bulk size-integrated NCCN ranged from ~500 cm−3 at SS = 0.15% to ~2100 cm−3 at SS = 0.70%, and the mean bulk NCCN / NCN ratio ranged from 0.16 at SS = 0.15% to 0.65 at SS = 0.70%. The average critical mobility diameters (D50) at SS = 0.15, 0.35, 0.50, and 0.70% were 116, 67, 56, and 46 nm, respectively. The corresponding average hygroscopic parameters (κCCN) were 0.39, 0.36, 0.31, and 0.28. The decrease in κCCN can be attributed to the increase in organic to inorganic volume ratio as particle size decreases, as measured by an Aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The κCCN correlates reasonably well with κAMS_SR based on size-resolved AMS measurements: κAMS_SR = κorg × forg + κinorg × finorg, where forg and finorg are the organic and inorganic volume fractions, respectively, κorg = 0.1 and κinorg = 0.6, with a R2 of 0.51. In closure analysis, NCCN was estimated by integrating the measured size-resolved NCN for particles larger than D50 derived from κ assuming internal mixing state. Estimates using κAMS_SR show that the measured and predicted NCCN were generally within 10% of each other at all four SS. The deviation increased to 26% when κAMS was calculated from bulk PM1 AMS measurements of particles because PM1 was dominated by particles of 200 to 500 nm in diameter, which had a larger inorganic fraction than those of D50 (particle diameter < 200 nm). A constant κ = 0.33 (the average value of κAMS_SR over the course of campaign) was found to give an NCCN prediction within 12% of the actual measured values. We also compared NCCN estimates based on the measured average D50 and the average size-resolved CCN activation ratio to examine the relative importance of hygroscopicity and mixing state. NCCN appears to be relatively more sensitive to the mixing state and hygroscopicity at a high SS = 0.70% and a low SS = 0.15%, respectively.

scholarly journals Hygroscopic mixing state of urban aerosol derived from size-resolved cloud condensation nuclei measurements during the MEGAPOLI campaign in Paris

2013 ◽  
Vol 13 (1) ◽  
pp. 2035-2075 ◽  
Author(s):  
Z. Jurányi ◽  
T. Tritscher ◽  
M. Gysel ◽  
M. Laborde ◽  
L. Gomes ◽  
...  
Keyword(s):  
Water Uptake ◽  
Cloud Condensation Nuclei ◽  
Pure Water ◽  
Particle Diameter ◽  
Complex Mixture ◽  
Average Particle ◽  
Hygroscopic Growth ◽  
Condensation Nuclei ◽  
Mixing State ◽  
Ambient Aerosols

Abstract. Ambient aerosols are a complex mixture of particles with different physical and chemical properties and consequently distinct hygroscopic behaviour. The hygroscopicity of a particle determines its water uptake at subsaturated relative humidity (RH) and its ability to form a cloud droplet at supersaturated RH. These processes influence the Earth's climate and the atmospheric lifetime of the particles. Cloud condensation nuclei (CCN) number size distributions (i.e. CCN number concentrations as a function of dry particle diameter) were measured close to Paris during the MEGAPOLI campaign in January–February 2010 covering 10 different supersaturations (SS = 0.1–1.0%). The time-resolved hygroscopic mixing state with respect to CCN activation was also derived from these measurements. Simultaneously, a Hygroscopicity Tandem Differential Mobility Analyser (HTDMA) was used to measure the hygroscopic growth factor (ratio of wet to dry mobility diameter) distributions at RH = 90%. The aerosol was highly externally mixed and its mixing state showed significant temporal variability. The average particle hygroscopicity was relatively low at subsaturation, RH = 90% (mean hygroscopicity parameter κ = 0.12–0.27) and increased with increasing dry diameter in the range 35–265 nm. The mean κ value, derived from the CCN measurements at supersaturation, ranged from 0.08 to 0.24 at SS = 1.0–0.%. Two types of mixing state resolved hygroscopicity closure studies were performed comparing the water uptake ability measured below and above saturation. In the first type the CCN counter was coupled with the HTDMA and closure was achieved over the whole range of probed dry diameters, growth factors and supersaturations using the κ-parameterisation for the water activity and assuming surface tension of pure water in the Köhler theory. In the second closure type we compared hygroscopicity distributions derived from parallel monodisperse CCN measurements and HTDMA measurements. Very good agreement was found at all supersaturations which shows that monodisperse CCN measurements are a reliable alternative to determine the hygroscopic mixing state of ambient aerosols.

scholarly journals External and internal cloud condensation nuclei (CCN) mixtures: controlled laboratory studies of varying mixing states

2019 ◽  
Vol 12 (8) ◽  
pp. 4277-4289 ◽  
Author(s):  
Diep Vu ◽  
Shaokai Gao ◽  
Tyler Berte ◽  
Mary Kacarab ◽  
Qi Yao ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Unknown Origin ◽  
Carbonaceous Aerosol ◽  
Condensation Nuclei ◽  
Mixing State ◽  
Flow Tube ◽  
Kohler Theory ◽  
Sigmoid Curve ◽  
Internal Particle ◽  
Mixing States

Abstract. Changes in aerosol chemical mixtures modify cloud condensation nuclei (CCN) activity. Previous studies have developed CCN models and validated changes in external and internal mixing state with ambient field data. Here, we develop an experimental method to test and validate the CCN activation of known aerosol chemical composition with multicomponent mixtures and varying mixing states. CCN activation curves consisting of one or more activation points are presented. Specifically, simplified two-component systems of varying hygroscopicity were generated under internal, external, and transitional mixing conditions. κ-Köhler theory predictions were calculated for different organic and inorganic mixtures and compared to experimentally derived kappa values and respective mixing states. This work employs novel experimental methods to provide information on the shifts in CCN activation data due to external to internal particle mixing from controlled laboratory sources. Results show that activation curves consisting of single and double activation points are consistent with internal and external mixtures, respectively. In addition, the height of the plateau at the activation points is reflective of the externally mixed concentration in the mixture. The presence of a plateau indicates that CCN activation curves consisting of multiple inflection points are externally mixed aerosols of varying water-uptake properties. The plateau disappears when mixing is promoted in the flow tube. At the end of the flow tube experiment, the aerosols are internally mixed and the CCN activated fraction data can be fit with a single-sigmoid curve. The technique to mimic externally to internally mixed aerosol is applied to non-hygroscopic carbonaceous aerosol with organic and inorganic components. To our knowledge, this work is the first to show controlled CCN activation of mixed non-hygroscopic soot with hygroscopic material as the aerosol population transitions from externally to internally mixed states in laboratory conditions. Results confirm that CCN activation analysis methods used here and in ambient data sets are robust and may be used to infer the mixing state of complex aerosol compositions of unknown origin.

scholarly journals The impact of aerosol size-dependent hygroscopicity and mixing state on the cloud condensation nuclei potential over the Northeast Atlantic

2021 ◽  
Author(s):  
Wei Xu ◽  
Kirsten N. Fossum ◽  
Jurgita Ovadnevaite ◽  
Chunshui Lin ◽  
Ru-Jin Huang ◽  
...  
Keyword(s):  
Biological Activity ◽  
Chemical Composition ◽  
Growth Factor ◽  
Cloud Condensation Nuclei ◽  
Condensation Nuclei ◽  
Mixing State ◽  
Northeast Atlantic ◽  
Size Dependent ◽  
Internal Mixing ◽  
The Impact

Abstract. We present an aerosol cloud condensation nuclei (CCN) closure study over the Northeast Atlantic Ocean using six approximating methods. The CCN number concentrations (NCCN) were measured at four discrete super-saturations (SS, 0.25, 0.5, 0.75 and 1.0 %). Concurrently, aerosol number size distribution, sub-saturation hygroscopic growth factor and bulk PM1 chemical composition were obtained at matching time resolution and after a careful data validation exercise. Method A used a constant bulk hygroscopicity parameter κ of 0.3; method B used bulk PM1 chemical composition measured by an aerosol mass spectrometer (AMS); method C and D utilized a single size (165 nm) growth factor (GF) measured by humidified tandem differential mobility analyzer (HTDMA); method C utilized size-dependent GFs measured at 35, 50, 75, 110 and 165 nm; method E divided the aerosol population into three hygroscopicity modes (near-hydrophobic, more-hygroscopic and sea-salt modes) and the total CCN number in each mode was cumulatively added up; method F used the full size scale GF probability density function (GF-PDF) in the most complex approach. The studied periods included high biological activity and low biological activity seasons in clean marine and polluted continental air masses to represent and discuss the most contrasting aerosol populations. Overall, a good agreement was found between estimated and measured NCCN with a linear regression slopes ranging from 0.64 and 1.6. The temporal variability was captured very well with Pearson's R value ranging from 0.76 to 0.98 depending on the method and air mass type. We further compared the results of using different methods to quantify the impact of size-dependent hygroscopicity and mixing state and found that ignoring size-dependent hygroscopicity induced overestimation of NCCN by up to 12 %, and ignoring a mixing state induced overestimation of NCCN by up to 15 %. The error induced by assuming an internal mixing in highly polluted cases was largely eliminated by dividing the full GF-PDf into three conventional hygroscopic modes while assuming an internal mixing in clean marine aerosol did not induced significant error.

scholarly journals Hygroscopic mixing state of urban aerosol derived from size-resolved cloud condensation nuclei measurements during the MEGAPOLI campaign in Paris

2013 ◽  
Vol 13 (13) ◽  
pp. 6431-6446 ◽  
Author(s):  
Z. Jurányi ◽  
T. Tritscher ◽  
M. Gysel ◽  
M. Laborde ◽  
L. Gomes ◽  
...  
Keyword(s):  
Water Uptake ◽  
Cloud Condensation Nuclei ◽  
Pure Water ◽  
Particle Diameter ◽  
Complex Mixture ◽  
Average Particle ◽  
Hygroscopic Growth ◽  
Condensation Nuclei ◽  
Mixing State ◽  
Ambient Aerosols

Abstract. Ambient aerosols are a complex mixture of particles with different physical and chemical properties and consequently distinct hygroscopic behaviour. The hygroscopicity of a particle determines its water uptake at subsaturated relative humidity (RH) and its ability to form a cloud droplet at supersaturated RH. These processes influence Earth's climate and the atmospheric lifetime of the particles. Cloud condensation nuclei (CCN) number size distributions (i.e. CCN number concentrations as a function of dry particle diameter) were measured close to Paris during the MEGAPOLI campaign in January–February 2010, covering 10 different supersaturations (SS = 0.1–1.0%). The time-resolved hygroscopic mixing state with respect to CCN activation was also derived from these measurements. Simultaneously, a hygroscopicity tandem differential mobility analyser (HTDMA) was used to measure the hygroscopic growth factor (ratio of wet to dry mobility diameter) distributions at RH = 90%. The aerosol was highly externally mixed and its mixing state showed significant temporal variability. The average particle hygroscopicity was relatively low at subsaturation (RH = 90%; mean hygroscopicity parameter κ = 0.12–0.27) and increased with increasing dry diameter in the range 35–265 nm. The mean κ value, derived from the CCN measurements at supersaturation, ranged from 0.08 to 0.24 at SS = 1.0–0.1%. Two types of mixing-state resolved hygroscopicity closure studies were performed, comparing the water uptake ability measured below and above saturation. In the first type the CCN counter was connected in series with the HTDMA and and closure was achieved over the whole range of probed dry diameters, growth factors and supersaturations using the κ-parametrization for the water activity and assuming surface tension of pure water in the Köhler theory. In the second closure type we compared hygroscopicity distributions derived from parallel monodisperse CCN measurements and HTDMA measurements. Very good agreement was found at all supersaturations, which shows that monodisperse CCN measurements are a reliable alternative to determine the hygroscopic mixing state of ambient aerosols.

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