Seasonal variation of CCN concentrations and aerosol activation properties in boreal forest

Abstract. As a part of EUCAARI activities, the annual cycle of cloud condensation nuclei (CCN) concentrations and critical diameter for cloud droplet activation as a function of supersaturation were measured using a CCN counter and a HTDMA (hygroscopic tandem DMA) at SMEAR II station, Hyytiälä, Finland. The critical diameters for cloud droplet activation were estimated from (i) the CCN concentration and particle size distribution data, and (ii) the hygroscopic growth factors by applying κ-Köhler theory. The critical diameters derived by these two methods were in good agreement with each other. The effect of new particle formation on the diurnal variation of CCN concentration and critical diameters was studied. New particle formation was observed to increase the CCN concentrations by 70–110%, depending on the supersaturation level. The average value for the κ-parameter determined from hygroscopicity measurements was κ = 0.18 and it predicted well the CCN activation in Hyytiälä boreal forest conditions. The derived critical diameters and κ-parameter indicate that aerosol particles at CCN sizes in Hyytiälä are mostly organic, but contain also more soluble, probably inorganic salts like ammonium sulphate, making the particles more CCN active than pure secondary organic aerosol.

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Seasonal variation of CCN concentrations and aerosol activation properties in boreal forest

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-13269-2011 ◽

2011 ◽

Vol 11 (24) ◽

pp. 13269-13285 ◽

Cited By ~ 84

Author(s):

S.-L. Sihto ◽

J. Mikkilä ◽

J. Vanhanen ◽

M. Ehn ◽

L. Liao ◽

...

Keyword(s):

Boreal Forest ◽

Cloud Condensation Nuclei ◽

Critical Diameter ◽

Cloud Droplet ◽

Particle Formation ◽

Distribution Data ◽

New Particle Formation ◽

Hygroscopic Growth ◽

Average Value ◽

Kohler Theory

Abstract. As a part of EUCAARI activities, the annual cycle of cloud condensation nuclei (CCN) concentrations and critical diameter for cloud droplet activation as a function of supersaturation were measured using a CCN counter and a HTDMA (hygroscopicity tandem differential mobility analyzer) at SMEAR II station, Hyytiälä, Finland. The critical diameters for CCN activation were estimated from (i) the measured CCN concentration and particle size distribution data, and (ii) the hygroscopic growth factors by applying κ-Köhler theory, in both cases assuming an internally mixed aerosol. The critical diameters derived by these two methods were in good agreement with each other. The effect of new particle formation on the diurnal variation of CCN concentration and critical diameters was studied. New particle formation was observed to increase the CCN concentrations by 70–110%, depending on the supersaturation level. The average value for the κ-parameter determined from hygroscopicity measurements was κ = 0.18 and it predicted well the CCN activation in boreal forest conditions in Hyytiälä. The derived critical diameters and κ-parameter confirm earlier findings with other methods, that aerosol particles at CCN sizes in Hyytiälä are mostly organic, but contain also more hygrosopic, probably inorganic salts like ammonium sulphate, making the particles more CCN active than pure secondary organic aerosol.

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Hygroscopic properties of ultrafine aerosol particles in the boreal forest: diurnal variation, solubility and the influence of sulfuric acid

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-9937-2006 ◽

2006 ◽

Vol 6 (5) ◽

pp. 9937-9965

Author(s):

M. Ehn ◽

T. Petäjä ◽

H. Aufmhoff ◽

P. Aalto ◽

K. Hämeri ◽

...

Keyword(s):

Sulfuric Acid ◽

Boreal Forest ◽

Cloud Condensation Nuclei ◽

Aerosol Particles ◽

Early Morning ◽

Particle Formation ◽

New Particle Formation ◽

Hygroscopic Growth ◽

Hygroscopic Properties ◽

Hygroscopic Particles

Abstract. Freshly formed atmospheric aerosol particles are neither large enough to efficiently scatter incoming solar radiation nor able to act as cloud condensation nuclei. As the particles grow larger, their hygroscopicity determines the limiting size after which they are important in both of the aforementioned processes. The condensing species resulting in growth alter the hygroscopicity of the particles. We have measured hygroscopic growth of aerosol particles present in a boreal forest, along with the very hygroscopic atmospheric trace gas sulfuric acid. The focus was on days with new particle formation by nucleation. The measured hygroscopic growth factors (GF) correlated positively with gaseous phase sulfuric acid concentrations. This correlation had a strong size dependency; the smaller the particle, the more condensing sulfuric acid is bound to alter the GF due to initially smaller mass. In addition, water uptake of nucleation mode particles was monitored during new particle formation events and followed during their growth to Aitken mode sizes. As the modal diameter increased, the solubility of the particles decreased. This indicated that initially more hygroscopic particles transformed into less hygroscopic or even hydrophobic particles. A similar behavior was seen also during days with no particle formation, with GF decreasing during the evenings and increasing during early morning. This can be tentatively explained by day- and nighttime differences in the hygroscopicity of condensable vapors.

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Hygroscopic properties of ultrafine aerosol particles in the boreal forest: diurnal variation, solubility and the influence of sulfuric acid

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-211-2007 ◽

2007 ◽

Vol 7 (1) ◽

pp. 211-222 ◽

Cited By ~ 82

Author(s):

M. Ehn ◽

T. Petäjä ◽

H. Aufmhoff ◽

P. Aalto ◽

K. Hämeri ◽

...

Keyword(s):

Sulfuric Acid ◽

Boreal Forest ◽

Diurnal Variation ◽

Gas Phase ◽

Aerosol Particles ◽

Particle Formation ◽

Time Of Day ◽

New Particle Formation ◽

Hygroscopic Growth ◽

Hygroscopic Properties

Abstract. The hygroscopic growth of aerosol particles present in a boreal forest was measured at a relative humidity of 88%. Simultaneously the gas phase concentration of sulfuric acid, a very hygroscopic compound, was monitored. The focus was mainly on days with new particle formation by nucleation. The measured hygroscopic growth factors (GF) correlated positively with the gaseous phase sulfuric acid concentrations. The smaller the particles, the stronger the correlation, with r=0.20 for 50 nm and r=0.50 for 10 nm particles. The increase in GF due to condensing sulfuric acid is expected to be larger for particles with initially smaller masses. During new particle formation, the changes in solubility of the new particles were calculated during their growth to Aitken mode sizes. As the modal diameter increased, the solubility of the particles decreased. This indicated that the initial particle growth was due to more hygroscopic compounds, whereas the later growth during the evening and night was mainly caused by less hygroscopic or even hydrophobic compounds. For all the measured sizes, a diurnal variation in GF was observed both during days with and without particle formation. The GF was lowest at around midnight, with a mean value of 1.12–1.24 depending on particle size and if new particle formation occurred during the day, and increased to 1.25–1.34 around noon. This can be tentatively explained by day- and nighttime gas-phase chemistry; different vapors will be present depending on the time of day, and through condensation these compounds will alter the hygroscopic properties of the particles in different ways.

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Atmospheric new particle formation as source of CCN in the Eastern Mediterranean marine boundary layer

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-11143-2015 ◽

2015 ◽

Vol 15 (7) ◽

pp. 11143-11178 ◽

Cited By ~ 1

Author(s):

N. Kalivitis ◽

V.-M. Kerminen ◽

G. Kouvarakis ◽

I. Stavroulas ◽

A. Bougiatioti ◽

...

Keyword(s):

Organic Material ◽

Marine Boundary Layer ◽

Size Range ◽

Eastern Mediterranean ◽

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Particle Formation ◽

New Particle Formation ◽

Multiple Sources ◽

Marine Air

Abstract. While Cloud Condensation Nuclei (CCN) production associated with atmospheric new particle formation (NPF) is thought to be frequent throughout the continental boundary layers, few studies on this phenomenon in marine air exist. Here, based on simultaneous measurement of particle number size distributions, CCN properties and aerosol chemical composition, we present the first direct evidence on CCN production resulting from NPF in the Eastern Mediterranean atmosphere. We show that condensation of both gaseous sulfuric acid and organic compounds from multiple sources leads to the rapid growth of nucleated particles to CCN sizes in this environment during the summertime. Sub-100 nm particles were found to be substantially less hygroscopic than larger particles during the period with active NPF and growth (0.2–0.4 lower κ between the 60 and 120 nm particles), probably due to enrichment of organic material in the sub-100 nm size range. The aerosol hygroscopicity tended to be at minimum just before the noon and at maximum in afternoon, which was very likely due to the higher sulfate to organic ratios and higher degree of oxidation of the organic material during the afternoon. Simultaneously to the formation of new particles during daytime, particles formed in the previous day or even earlier were growing into the size range relevant to cloud droplet activation, and the particles formed in the atmosphere were possibly mixed with long-range transported particles.

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Evaluation of the contribution of new particle formation to cloud droplet in urban atmosphere

10.5194/acp-2021-23 ◽

2021 ◽

Author(s):

Sihui Jiang ◽

Fang Zhang ◽

Jingye Ren ◽

Lu Chen ◽

Xing Yan ◽

...

Keyword(s):

Water Vapor ◽

Cloud Condensation Nuclei ◽

Aerosol Particles ◽

Cloud Droplet ◽

Particle Formation ◽

Urban Atmosphere ◽

Primary Sources ◽

New Particle Formation ◽

Multiple Sources ◽

Considerable Impact

Abstract. New particle formation (NPF) is a large source of cloud condensation nuclei (CCN) and cloud droplet in the troposphere. In this study, we quantified the contribution of NPF to cloud droplet number concentration (CDNC, or Nd) at typical updraft velocities (V) in clouds using a field campaign data of aerosol number size distribution and chemical composition observed on May 25–June 18, 2017 in urban Beijing. We show that the NPF drives the variations of CCN and cloud droplet and increases Nd by 30–33 % at V = 0.3–3 m s−1 in urban atmosphere. A markedly reduction in Nd is observed due to water vapor competition with consideration of actual environmental updraft velocity, decreasing by 11.8 ± 5.0 % at V = 3 m s−1 and 19.0 ± 4.5 % at V = 0.3 m s−1 compared to that from a prescribed supersaturation. The effect of water vapor competition becomes smaller at larger V that can provide more sufficient water vapor. Essentially, water vapor competition led to the reduction in Nd by decreasing the environmental maximum supersaturation (Smax) for the activation of aerosol particles. It is shown that Smax was decreased by 14.5–11.7 % for V = 0.3–3 m s−1. Particularly, the largest suppression of cloud droplet formation due to the water vapor competition is presented at extremely high aerosol particle number concentrations. As a result, although a larger increase of CCN-size particles by NPF event is derived on clean NPF day when pre-existing background aerosol particles are very low, there is no large discrepancy in the enhancement of Nd by NPF between the clean and polluted NPF day. We finally show a considerable impact of the primary sources when evaluating the NPF contribution to cloud droplet based on a case study. Our study highlights the importance of fully consideration of both the environmental meteorological conditions and multiple sources (i.e. secondary and primary) to evaluate the NPF effect on clouds and the associated climate effects in polluted regions.

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Atmospheric new particle formation as a source of CCN in the eastern Mediterranean marine boundary layer

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-9203-2015 ◽

2015 ◽

Vol 15 (16) ◽

pp. 9203-9215 ◽

Cited By ~ 24

Author(s):

N. Kalivitis ◽

V.-M. Kerminen ◽

G. Kouvarakis ◽

I. Stavroulas ◽

A. Bougiatioti ◽

...

Keyword(s):

Organic Material ◽

Marine Boundary Layer ◽

Size Range ◽

Eastern Mediterranean ◽

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Particle Formation ◽

New Particle Formation ◽

Multiple Sources ◽

Marine Air

Abstract. While cloud condensation nuclei (CCN) production associated with atmospheric new particle formation (NPF) is thought to be frequent throughout the continental boundary layers, few studies on this phenomenon in marine air exist. Here, based on simultaneous measurement of particle number size distributions, CCN properties and aerosol chemical composition, we present the first direct evidence on CCN production resulting from NPF in the eastern Mediterranean atmosphere. We show that condensation of both gaseous sulfuric acid and organic compounds from multiple sources leads to the rapid growth of nucleated particles to CCN sizes in this environment during the summertime. Sub-100 nm particles were found to be substantially less hygroscopic than larger particles during the period with active NPF and growth (the value of κ was lower by 0.2–0.4 for 60 nm particles compared with 120 nm particles), probably due to enrichment of organic material in the sub-100 nm size range. The aerosol hygroscopicity tended to be at minimum just before the noon and at maximum in the afternoon, which was very likely due to the higher sulfate-to-organic ratios and higher degree of oxidation of the organic material during the afternoon. Simultaneous with the formation of new particles during daytime, particles formed during the previous day or even earlier were growing into the size range relevant to cloud droplet activation, and the particles formed in the atmosphere were possibly mixed with long-range-transported particles.

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Secondary new particle formation in Northern Finland Pallas site between the years 2000 and 2010

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-12959-2011 ◽

2011 ◽

Vol 11 (24) ◽

pp. 12959-12972 ◽

Cited By ~ 59

Author(s):

E. Asmi ◽

N. Kivekäs ◽

V.-M. Kerminen ◽

M. Komppula ◽

A.-P. Hyvärinen ◽

...

Keyword(s):

Growth Rates ◽

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Detailed Examination ◽

Particle Formation ◽

New Particle Formation ◽

Air Masses ◽

Event Frequency ◽

Marine Air

Abstract. Secondary new particle formation affects atmospheric aerosol and cloud droplet numbers and thereby, the aerosol effects on climate. In this paper, the frequency of nucleation events and the associated particle formation and growth rates, along with their seasonal variation, was analysed based on over ten years of aerosol measurements conducted at the Pallas GAW station in northern Finland. The long-term measurements also allowed a detailed examination of factors possibly favouring or suppressing particle formation. Effects of meteorological parameters and air mass properties as well as vapour sources and sinks for particle formation frequency and event parameters were inspected. In addition, the potential of secondary particle formation to increase the concentration of cloud condensation nuclei (CCN) sized particles was examined. Findings from these long-term measurements confirmed previous observations: event frequency peaked in spring and the highest growth rates were observed in summer, affiliated with increased biogenic activity. Events were almost exclusively observed in marine air masses on sunny cloud-free days. A low vapour sink by the background particle population as well as an elevated sulphuric acid concentration were found to favour particle formation. These were also conditions taking place most likely in marine air masses. Inter-annual trend showed a minimum in event frequency in 2003, when also the smallest annual median of growth rate was observed. This gives further evidence of the importance and sensitivity of particle formation for the condensing vapour concentrations at Pallas site. The particle formation was observed to increase CCN80 (>80 nm particle number) concentrations especially in summer and autumn seasons when the growth rates were the highest. When the growing mode exceeded the selected 80 nm limit, on average in those cases, 211 ± 114% increase of CCN80 concentrations was observed.

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New particle formation in the southern Aegean Sea during the Etesians: importance for CCN production and cloud droplet number

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-175-2017 ◽

2017 ◽

Vol 17 (1) ◽

pp. 175-192 ◽

Cited By ~ 21

Author(s):

Panayiotis Kalkavouras ◽

Elissavet Bossioli ◽

Spiros Bezantakos ◽

Aikaterini Bougiatioti ◽

Nikos Kalivitis ◽

...

Keyword(s):

Water Vapor ◽

Eastern Mediterranean ◽

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Aegean Sea ◽

Particle Formation ◽

Cloud Formation ◽

Particle Nucleation ◽

Surface Winds ◽

New Particle Formation

Abstract. This study examines how new particle formation (NPF) in the eastern Mediterranean in summer affects CCN (cloud condensation nuclei) concentrations and cloud droplet formation. For this, the concentration and size distribution of submicron aerosol particles, along with the concentration of trace gases and meteorological variables, were studied over the central (Santorini) and southern Aegean Sea (Finokalia, Crete) from 15 to 28 July 2013, a period that includes Etesian events and moderate northern surface winds. Particle nucleation bursts were recorded during the Etesian flow at both stations, with those observed at Santorini reaching up to 1.5  ×  104 particles cm−3; the fraction of nucleation-mode particles over Crete was relatively diminished, but a higher number of Aitken-mode particles were observed as a result of aging. Aerosol and photochemical pollutants covaried throughout the measurement period; lower concentrations were observed during the period of Etesian flow (e.g., 43–70 ppbv for ozone and 1.5–5.7 µg m−3 for sulfate) but were substantially enhanced during the period of moderate surface winds (i.e., increase of up to 32 for ozone and 140 % for sulfate). We find that NPF can double CCN number (at 0.1 % supersaturation), but the resulting strong competition for water vapor in cloudy updrafts decreases maximum supersaturation by 14 % and augments the potential droplet number only by 12 %. Therefore, although NPF events may strongly elevate CCN numbers, the relative impacts on cloud droplet number (compared to pre-event levels) is eventually limited by water vapor availability and depends on the prevailing cloud formation dynamics and the aerosol levels associated with the background of the region.

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New particle formation events persistently reduce cloud droplets in boundary layer clouds

10.5194/egusphere-egu2020-13194 ◽

2020 ◽

Author(s):

David Patoulias ◽

Kalliopi Florou ◽

Spyros N. Pandis ◽

Athanasios Nenes

Keyword(s):

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Particle Formation ◽

New Particle Formation ◽

Cloud Droplets ◽

Convective Clouds ◽

Boundary Layer Clouds ◽

Stratiform Clouds ◽

Local Warming ◽

Climate Cooling

<p>&#913; considerable fraction of cloud condensation nuclei (CCN) originates from new particle formation (NPF). Because of this, NPF events themselves are thought to also increase CCN and cloud droplet number (CDN) and contribute to climate cooling. High resolution state-of-the-art simulations over Europe however portray a different view: radiatively important stratiform clouds influenced by NPF events experience a systematic and substantial decrease in droplet number during and after nucleation events. The drop in CDN occurs because particles present prior to the NPF experiences slower growth during and after each event (as the condensable material is consumed by the growth of the NPF particles that do not typically activate), leading to fewer CCN at the low supersaturation levels characteristic of stratiform clouds (~0.1%). Convective clouds, however, tend to experience a modest increase in cloud droplet number &#8211; consistent with established views on the NPF-cloud link. Our results are corroborated by published observational evidence and all together reshape our conceptual understanding of NPF events on clouds, where droplets in stratiform clouds tend to be reduced (leading to local warming from reductions in cloud albedo) but enhance in convection. Combined, these effects could bear important impacts on cloud structure following NPF events.</p>

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Regional new particle formation as modulators of cloud condensation nuclei and cloud droplet number in the eastern Mediterranean

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-6185-2019 ◽

2019 ◽

Vol 19 (9) ◽

pp. 6185-6203 ◽

Cited By ~ 8

Author(s):

Panayiotis Kalkavouras ◽

Aikaterini Bougiatioti ◽

Nikos Kalivitis ◽

Iasonas Stavroulas ◽

Maria Tombrou ◽

...

Keyword(s):

Eastern Mediterranean ◽

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Particle Formation ◽

Cloud Formation ◽

New Particle Formation ◽

Condensation Nuclei ◽

Low Cloud ◽

Condensational Growth ◽

The Impact

Abstract. A significant fraction of atmospheric particles that serve as cloud condensation nuclei (CCN) are thought to originate from the condensational growth of new particle formation (NPF) from the gas phase. Here, 7 years of continuous aerosol and meteorological measurements (June 2008 to May 2015) at a remote background site of the eastern Mediterranean were recorded and analyzed to assess the impact of NPF (of 162 episodes identified) on CCN and cloud droplet number concentration (CDNC) formation in the region. A new metric is introduced to quantitatively determine the initiation and duration of the influence of NPF on the CCN spectrum. NPF days were found to increase CCN concentrations (from 0.10 % to 1.00 % supersaturation) between 29 % and 77 %. Enhanced CCN concentrations from NPF are mostly observed, as expected, under low preexisting particle concentrations and occur in the afternoon, relatively later in the winter and autumn than in the summer. Potential impacts of NPF on cloud formation were quantified by introducing the observed aerosol size distributions and chemical composition into an established cloud droplet parameterization. We find that the supersaturations that develop are very low (ranging between 0.03 % and 0.27 %) for typical boundary layer dynamics (σw ∼0.3 m s−1) and NPF is found to enhance CDNC by a modest 13 %. This considerable contrast between CCN and CDNC response is in part from the different supersaturation levels considered, but also because supersaturation drops from increasing CCN because of water vapor competition effects during the process of droplet formation. The low cloud supersaturation further delays the appearance of NPF impacts on CDNC to clouds formed in the late evening and nighttime – which has important implications for the extent and types of indirect effects induced by NPF events. An analysis based on CCN concentrations using prescribed supersaturation can provide very different, even misleading, conclusions and should therefore be avoided. The proposed approach here offers a simple, yet highly effective way for a more realistic impact assessment of NPF events on cloud formation.

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