scholarly journals The important roles of surface tension and growth rate in the contribution of new particle formation (NPF) to cloud condensation nuclei (CCN) number concentration: evidence from field measurements in southern China

2020 ◽  
Author(s):  
Mingfu Cai ◽  
Baoling Liang ◽  
Qibin Sun ◽  
Li Liu ◽  
Bin Yuan ◽  
...  
Keyword(s):  
Surface Tension ◽  
Growth Rate ◽  
Cloud Condensation Nuclei ◽  
Formation Rate ◽  
High Growth ◽  
High Growth Rate ◽  
Number Concentration ◽  
Condensation Nuclei ◽  
Scanning Mobility Particle Sizer ◽  
Particle Sizer

Abstract. The contribution of new particle formation (NPF) to cloud condensation nuclei (CCN) number concentration varies largely under different environments, depending on several key factors such as formation rate (J), growth rate (GR), distribution of preexisting particles and properties of new particles during NPF events. This study investigated the contribution of NPF to the NCCN and its controlling factors based on measurements conducted at the Heshan supersite, in the Pearl River Delta (PRD) region of China during fall-time 2019. The size-resolved cloud condensation nuclei activity and size-resolved particle hygroscopicity were measured by a cloud condensation nuclei counter (CCNc) and a hygroscopic tandem differential mobility analyzer (HTDMA), respectively, along with a scanning mobility particle sizer (SMPS) and a diethylene glycol scanning mobility particle sizer (DEG-SMPS) for particle number size distribution (PNSD). A typical NPF event on 29th October was chosen to investigate the contribution of the NPF to NCCN under several supersaturation ratios. Two particle properties (hygroscopicity and surface tension) affect CCN activation with the latter being more important in terms of the CCN concentration (NCCN). A lower value of surface tension (i.e., 0.06 N m−1) than pure water assumption (0.073 N m−1) could increase the NCCN at SS = 1.0 % by about 20 % during non-event period and by about 40 % during the event. In addition, an earlier peak time corresponding to a lower critical diameter (D50) was also observed. The results show that high formation rate, growth rate, and low background particle concentration lead to high number concentrations of newly-formed particles. The high growth rate was found to have the most profound impact on the NCCN which can be attributed to the facts that a higher growth rate can grow particles to the CCN size in a shorter time before they are scavenged by pre-existing particles. Two other NPF events (an event on 18th October in this campaign and an event on 12th December, 2014 in Panyu) were chosen to perform sensitivity tests under different scenarios (growth rate, formation rate, and background particle concertation). The calculated NCCN at SS = 1.0 % on 12th December, 2014 was significantly lower than that from the other two events. The event on 12th December was re-simulated using high growth rate taken from the event on 18th October which resulted in similar CCN concentrations between the two events (12th December and 18th October), implying that the growth rate is the most controlling factor for CCN activation. Our results highlight the importance of growth rate and surface tension when evaluating the contribution of NPF to the NCCN.

scholarly journals The important roles of surface tension and growth rate in the contribution of new particle formation (NPF) to cloud condensation nuclei (CCN) number concentration: evidence from field measurements in southern China

2021 ◽  
Vol 21 (11) ◽  
pp. 8575-8592
Author(s):  
Mingfu Cai ◽  
Baoling Liang ◽  
Qibin Sun ◽  
Li Liu ◽  
Bin Yuan ◽  
...  
Keyword(s):  
Surface Tension ◽  
Growth Rate ◽  
Particle Concentration ◽  
Cloud Condensation Nuclei ◽  
Formation Rate ◽  
Number Concentration ◽  
Condensation Nuclei ◽  
Scanning Mobility Particle Sizer ◽  
Particle Sizer ◽  
Background Particle

Abstract. The contribution of new particle formation (NPF) to cloud condensation nuclei (CCN) number concentration (NCCN) varies largely under different environments and depends on several key factors such as formation rate (J), growth rate (GR), distribution of preexisting particles, and properties of new particles during NPF events. This study investigates the contribution of NPF to the NCCN and its controlling factors based on measurements conducted at the Heshan supersite, in the Pearl River Delta (PRD) region of China during fall 2019. The size-resolved cloud condensation nuclei activity and size-resolved particle hygroscopicity were measured by a cloud condensation nuclei counter (CCNc) and a hygroscopic tandem differential mobility analyzer (HTDMA), respectively, along with a scanning mobility particle sizer (SMPS) and a diethylene glycol scanning mobility particle sizer (DEG-SMPS) for particle number size distribution (PNSD). A typical NPF event on 29 October was chosen to investigate the contribution of the NPF to NCCN under several supersaturation (SS) ratios. Two particle properties (hygroscopicity and surface tension) affect CCN activation with the latter being more important in terms of the CCN concentration (NCCN). A lower value of surface tension (i.e., 0.06 N m−1) than the pure-water assumption (0.073 N m−1) could increase the NCCN at SS  =  1.0 % by about 20 % during the nonevent period and by about 40 % during the event. In addition, an earlier peak time corresponding to a lower critical diameter (D50) was also observed. The results show that high formation rate, growth rate, and low background particle concentration lead to high number concentrations of newly formed particles. The high growth rate was found to have the most significant impact on the NCCN, which can be attributed to the fact that a higher growth rate can grow particles to the CCN size in a shorter time before they are scavenged by preexisting particles. Two other NPF events (an event on 18 October in this campaign and an event on 12 December 2014 in Panyu) were chosen to perform sensitivity tests under different scenarios (growth rate, formation rate, and background particle concentration). The calculated NCCN at SS = 1.0 % on 12 December 2014 was significantly lower than that from the other two events. The event on 12 December was re-simulated using the growth rate taken from the event on 18 October which resulted in similar CCN concentrations between the two events (12 December and 18 October), implying that the growth rate is the major impact factor for CCN activation. Our results highlight the importance of growth rate and surface tension when evaluating the contribution of NPF to the NCCN.

scholarly journals Assessment of cloud supersaturation by size-resolved aerosol particle and cloud condensation nuclei (CCN) measurements

2014 ◽  
Vol 7 (8) ◽  
pp. 2615-2629 ◽  
Author(s):  
M. L. Krüger ◽  
S. Mertes ◽  
T. Klimach ◽  
Y. F. Cheng ◽  
H. Su ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Aerosol Size Distribution ◽  
Distribution Data ◽  
Research Station ◽  
Condensation Nuclei ◽  
Scanning Mobility Particle Sizer ◽  
Average Value ◽  
Alpine Research ◽  
Particle Sizer

Abstract. In this study we show how size-resolved measurements of aerosol particles and cloud condensation nuclei (CCN) can be used to characterize the supersaturation of water vapor in a cloud. The method was developed and applied during the ACRIDICON-Zugspitze campaign (17 September to 4 October 2012) at the high-Alpine research station Schneefernerhaus (German Alps, 2650 m a.s.l.). Number size distributions of total and interstitial aerosol particles were measured with a scanning mobility particle sizer (SMPS), and size-resolved CCN efficiency spectra were recorded with a CCN counter system operated at different supersaturation levels. During the evolution of a cloud, aerosol particles are exposed to different supersaturation levels. We outline and compare different estimates for the lower and upper bounds (Slow, Shigh) and the average value (Savg) of peak supersaturation encountered by the particles in the cloud. A major advantage of the derivation of Slow and Savg from size-resolved CCN efficiency spectra is that it does not require the specific knowledge or assumptions about aerosol hygroscopicity that are needed to derive estimates of Slow, Shigh, and Savg from aerosol size distribution data. For the investigated cloud event, we derived Slow ≈ 0.07–0.25%, Shigh ≈ 0.86–1.31% and Savg ≈ 0.42–0.68%.

scholarly journals Assessment of cloud supersaturation by aerosol particle and cloud condensation nuclei (CCN) measurements

2013 ◽  
Vol 6 (6) ◽  
pp. 10021-10056 ◽  
Author(s):  
M. L. Krüger ◽  
S. Mertes ◽  
T. Klimach ◽  
Y. Cheng ◽  
H. Su ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Aerosol Size Distribution ◽  
Distribution Data ◽  
Research Station ◽  
Condensation Nuclei ◽  
Scanning Mobility Particle Sizer ◽  
Average Value ◽  
Alpine Research ◽  
Particle Sizer

Abstract. In this study we show how size-resolved measurements of aerosol particles and cloud condensation nuclei (CCN) can be used to characterize the supersaturation of water vapor in a cloud. The method was developed and applied for the investigation of a cloud event during the ACRIDICON-Zugspitze campaign (17 September to 4 October 2012) at the high-alpine research station Schneefernerhaus (German Alps, 2650 m a.s.l.). Number size distributions of total and interstitial aerosol particles were measured with a scanning mobility particle sizer (SMPS), and size-resolved CCN efficiency spectra were recorded with a CCN counter system operated at different supersaturation levels. During the evolution of a cloud, aerosol particles are exposed to different supersaturation levels. We outline and compare different estimates for the lower and upper bounds (Slow, Shigh) and the average value (Savg) of peak supersaturation encountered by the particles in the cloud. For the investigated cloud event, we derived Slow ≈ 0.19–0.25%, Shigh ≈ 0.90–1.64% and Savg ≈ 0.38–0.84%. Estimates of Slow, Shigh and Savg based on aerosol size distribution data require specific knowledge or assumptions of aerosol hygroscopicity, which are not required for the derivation of Slow and Savg from the size-resolved CCN efficiency spectra.

Exploring SiC Growth Limitation of Vapor-Liquid-Solid Mechanism when Using Two Different Carbon Precursors

2013 ◽  
Vol 740-742 ◽  
pp. 323-326
Author(s):  
Kassem Alassaad ◽  
François Cauwet ◽  
Davy Carole ◽  
Véronique Soulière ◽  
Gabriel Ferro
Keyword(s):  
Growth Rate ◽  
High Growth ◽  
High Growth Rate ◽  
Carbon Precursor ◽  
Growth Limitation ◽  
Vapor Liquid Solid ◽  
Partial Pressures ◽  
Vapor Liquid Solid Mechanism ◽  
Vls Growth ◽  
Vapor Liquid

Abstract. In this paper, conditions for obtaining high growth rate during epitaxial growth of SiC by vapor-liquid-solid mechanism are investigated. The alloys studied were Ge-Si, Al-Si and Al-Ge-Si with various compositions. Temperature was varied between 1100 and 1300°C and the carbon precursor was either propane or methane. The variation of layers thickness was studied at low and high precursor partial pressure. It was found that growth rates obtained with both methane and propane are rather similar at low precursor partial pressures. However, when using Ge based melts, the use of high propane flux leads to the formation of a SiC crust on top of the liquid, which limits the growth by VLS. But when methane is used, even at extremely high flux (up to 100 sccm), no crust could be detected on top of the liquid while the deposit thickness was still rather small (between 1.12 μm and 1.30 μm). When using Al-Si alloys, no crust was also observed under 100 sccm methane but the thickness was as high as 11.5 µm after 30 min growth. It is proposed that the upper limitation of VLS growth rate depends mainly on C solubility of the liquid phase.

Very High Growth Rate of 4H-SiC Using MTS as Chloride-Based Precursor

2008 ◽  
Vol 600-603 ◽  
pp. 115-118 ◽  
Author(s):  
Henrik Pedersen ◽  
Stefano Leone ◽  
Anne Henry ◽  
Franziska Christine Beyer ◽  
Vanya Darakchieva ◽  
...  
Keyword(s):  
Growth Rate ◽  
Linear Dependence ◽  
Growth Rates ◽  
Molar Fraction ◽  
High Growth ◽  
High Growth Rate ◽  
Epitaxial Layers ◽  
Single Precursor ◽  
Very High

The chlorinated precursor methyltrichlorosilane (MTS), CH3SiCl3, has been used to grow epitaxial layers of 4H-SiC in a hot wall CVD reactor, with growth rates as high as 170 µm/h at 1600°C. Since MTS contains both silicon and carbon, with the C/Si ratio 1, MTS was used both as single precursor and mixed with silane or ethylene to study the effect of the C/Si and Cl/Si ratios on growth rate and doping of the epitaxial layers. When using only MTS as precursor, the growth rate showed a linear dependence on the MTS molar fraction in the reactor up to about 100 µm/h. The growth rate dropped for C/Si < 1 but was constant for C/Si > 1. Further, the growth rate decreased with lower Cl/Si ratio.

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