Chemical composition and droplet size distribution of cloud at the summit of Mount Tai, China

Abstract. The chemical composition of 39 cloud samples and droplet size distributions in 24 cloud events were investigated at the summit of Mt. Tai from July to October 2014. Inorganic ions, organic acids, metals, HCHO, H2O2, sulfur(IV), organic carbon, and elemental carbon as well as pH and electrical conductivity were analyzed. The acidity of the cloud water significantly decreased from a reported value of pH 3.86 during 2007–2008 (Guo et al., 2012) to pH 5.87 in the present study. The concentrations of nitrate and ammonium were both increased since 2007–2008, but the overcompensation of ammonium led to an increase in the mean pH value. The microphysical properties showed that cloud droplets were smaller than 26.0 µm and most were in the range of 6.0–9.0 µm at Mt. Tai. The maximum droplet number concentration (Nd) was associated with a droplet size of 7.0 µm. High liquid water content (LWC) values could facilitate the formation of larger cloud droplets and broadened the droplet size distribution. Cloud droplets exhibited a strong interaction with atmospheric aerosols. Higher PM2. 5 levels resulted in higher concentrations of water-soluble ions and smaller sizes with increased numbers of cloud droplets. The lower pH values were likely to occur at higher PM2. 5 concentrations. Clouds were an important sink for soluble materials in the atmosphere. The dilution effect of cloud water should be considered when estimating concentrations of soluble components in the cloud phase.

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Chemical composition and droplet size distribution of cloud at the summit of Mount Tai, China

10.5194/acp-2016-1175 ◽

2017 ◽

Author(s):

Jiarong Li ◽

Xinfeng Wang ◽

Jianmin Chen ◽

Chao Zhu ◽

Weijun Li ◽

...

Keyword(s):

Chemical Composition ◽

Size Distribution ◽

Droplet Size ◽

Atmospheric Aerosols ◽

Ph Value ◽

Inorganic Ions ◽

Droplet Size Distribution ◽

Dilution Effect ◽

Water Soluble ◽

Cloud Droplets

Abstract. Chemical composition of 39 cloud samples and droplet size distribution in 24 cloud events were investigated at the summit of Mt. Tai from July to October 2014. Inorganic ions, organic acids, metals, HCHO, H2O2, sulfur(IV), organic carbon, element carbon as well as pH and electrical conductivity were analyzed. The acidity of the cloud water significantly decreased from a reported value of pH 3.86 in 2007–2008 (Guo et al., 2012) to pH 5.87 in the present study. The concentrations of nitrate and ammonium were both increased since 2007–2008, but the overcompensation of ammonium led to the increase of the mean pH value. The microphysical properties showed that cloud droplets were smaller than 26.0 μm and the most were in the range of 6.0–9.0 μm. The maximum droplet number concentration (Nd) was associated with droplet sizes of 7.0 μm. Cloud droplets exhibited a strong interaction with atmospheric aerosols. High PM2.5 level resulted in higher concentrations of water soluble ions and smaller sizes with more numbers of cloud droplets, and further gave rise to relatively high acidity. High degrees of relative humidity facilitated the formation of large cloud droplets and led to high liquid water contents under low PM2.5 level. The cloud droplets to wet deposition acted as an important sink of soluble material in the atmosphere and the dilution effect of the water content should be considered when estimating concentrations of soluble components in the cloud phase.

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A Comprehensive Approach from Interfacial to Bulk Properties of Legume Protein-Stabilized Emulsions

Fluids ◽

10.3390/fluids4020065 ◽

2019 ◽

Vol 4 (2) ◽

pp. 65 ◽

Cited By ~ 2

Author(s):

Manuel Félix ◽

Alberto Romero ◽

Cecilio Carrera-Sanchez ◽

Antonio Guerrero

Keyword(s):

Rheological Properties ◽

Size Distribution ◽

Droplet Size ◽

Electrostatic Interactions ◽

Ph Value ◽

Droplet Size Distribution ◽

Interfacial Properties ◽

Industrial Applications ◽

Droplet Sizes ◽

Legume Protein

The correlation between interfacial properties and emulsion microstructure is a topic of special interest that has many industrial applications. This study deals with the comparison between the rheological properties of oil-water interfaces with adsorbed proteins from legumes (chickpea or faba bean) and the properties of the emulsions using them as the only emulsifier, both at microscopic (droplet size distribution) and macroscopic level (linear viscoelasticity). Two different pH values (2.5 and 7.5) were studied as a function of storage time. Interfaces were characterized by means of dilatational and interfacial shear rheology measurements. Subsequently, the microstructure of the final emulsions obtained was evaluated thorough droplet size distribution (DSD), light scattering and rheological measurements. Results obtained evidenced that pH value has a strong influence on interfacial properties and emulsion microstructure. The best interfacial results were obtained for the lower pH value using chickpea protein, which also corresponded to smaller droplet sizes, higher viscoelastic moduli, and higher emulsion stability. Thus, results put forward the relevance of the interfacial tension values, the adsorption kinetics, the viscoelastic properties of the interfacial film, and the electrostatic interactions among droplets, which depend on pH and the type of protein, on the microstructure, rheological properties, and stability of legume protein-stabilized emulsions.

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Cloud water composition in relation to the droplet size distribution and cloud base altitude

Journal of Aerosol Science ◽

10.1016/s0021-8502(00)90311-2 ◽

2000 ◽

Vol 31 ◽

pp. 301-302

Author(s):

W. Wieprecht ◽

D. Moeller ◽

K. Acker ◽

R. Auel ◽

D. Kalass

Keyword(s):

Size Distribution ◽

Droplet Size ◽

Droplet Size Distribution ◽

Cloud Water ◽

Cloud Base ◽

Water Composition

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Turbulence Effects of Collision Efficiency and Broadening of Droplet Size Distribution in Cumulus Clouds

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-17-0123.1 ◽

2018 ◽

Vol 75 (1) ◽

pp. 203-217 ◽

Cited By ~ 18

Author(s):

Sisi Chen ◽

M. K. Yau ◽

Peter Bartello

Keyword(s):

Size Distribution ◽

Droplet Size ◽

Droplet Size Distribution ◽

Droplet Growth ◽

Small Scale ◽

Cumulus Clouds ◽

Collision Efficiency ◽

Cloud Droplets ◽

R Ratio ◽

Condensational Growth

This paper aims to investigate and quantify the turbulence effect on droplet collision efficiency and explore the broadening mechanism of the droplet size distribution (DSD) in cumulus clouds. The sophisticated model employed in this study individually traces droplet motions affected by gravity, droplet disturbance flows, and turbulence in a Lagrangian frame. Direct numerical simulation (DNS) techniques are implemented to resolve the small-scale turbulence. Collision statistics for cloud droplets of radii between 5 and 25 μm at five different turbulence dissipation rates (20–500 cm2 s−3) are computed and compared with pure-gravity cases. The results show that the turbulence enhancement of collision efficiency highly depends on the r ratio (defined as the radius ratio of collected and collector droplets r/ R) but is less sensitive to the size of the collector droplet investigated in this study. Particularly, the enhancement is strongest among comparable-sized collisions, indicating that turbulence can significantly broaden the narrow DSD resulting from condensational growth. Finally, DNS experiments of droplet growth by collision–coalescence in turbulence are performed for the first time in the literature to further illustrate this hypothesis and to monitor the appearance of drizzle in the early rain-formation stage. By comparing the resulting DSDs at different turbulence intensities, it is found that broadening is most pronounced when turbulence is strongest and similar-sized collisions account for 21%–24% of total collisions in turbulent cases compared with only 9% in the gravitational case.

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Influence of pH value on microstructure of oil-in-water emulsions stabilized by chickpea protein flour

Food Science and Technology International ◽

10.1177/1082013218774707 ◽

2018 ◽

Vol 24 (7) ◽

pp. 555-563 ◽

Cited By ~ 3

Author(s):

Manuel Felix ◽

Nadia Isurralde ◽

Alberto Romero ◽

Antonio Guerrero

Keyword(s):

Size Distribution ◽

Droplet Size ◽

Protein Concentration ◽

Ph Value ◽

Droplet Size Distribution ◽

Laser Scanning Microscopy ◽

Plant Proteins ◽

Small Amplitude Oscillatory Shear ◽

Oil In Water ◽

Influence Of Ph

Food industry is highly interested in the development of healthier formulations of oil-in-water emulsions, stabilized by plant proteins instead of egg or milk proteins. These emulsions would avoid allergic issues or animal fat. Among other plant proteins, legumes are a cost-competitive product. This work evaluates the influence of pH value (2.5, 5.0 and 7.5) on emulsions stabilized by chickpea-based emulsions at two different protein concentration (2.0 and 4.0 wt%). Microstructure of chickpea-based emulsions is assessed by means of backscattering, droplet size distributions and small amplitude oscillatory shear measurements. Visual appearances as well as confocal laser scanning microscopy images are obtained to provide useful information on the emulsions structure. Interestingly, results indicate that the pH value and protein concentration have a strong influence on emulsion microstructure and stability. Thus, the system which contains protein surfaces positively charged shows the highest viscoelastic properties, a good droplet size distribution profile and non-apparent destabilization phenomena. Interestingly, results also reveal the importance of rheological measurements in the prediction of protein interactions and emulsion stability since this technique is able to predict destabilization mechanisms sooner than other techniques such as backscattering or droplet size distribution measurements.

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A New Mechanism of Droplet Size Distribution Broadening during Diffusional Growth

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-12-0182.1 ◽

2013 ◽

Vol 70 (7) ◽

pp. 2051-2071 ◽

Cited By ~ 22

Author(s):

Alexei Korolev ◽

Mark Pinsky ◽

Alex Khain

Keyword(s):

Size Distribution ◽

Droplet Size ◽

Initial Conditions ◽

Droplet Size Distribution ◽

Cloud Base ◽

Diffusional Growth ◽

Cloud Droplets ◽

Droplet Concentration ◽

Droplet Sizes ◽

Precipitation Formation

Abstract A new mechanism has been developed for size distribution broadening toward large droplet sizes. This mechanism may explain the rapid formation of large cloud droplets, which may subsequently trigger precipitation formation through the collision–coalescence process. The essence of the new mechanism consists of a sequence of mixing events between ascending and descending parcels. When adiabatically ascending and descending parcels having the same initial conditions at the cloud base arrive at the same level, they will have different droplet sizes and temperatures, as well as different supersaturations. Isobaric mixing between such parcels followed by further ascents and descents enables the enhanced growth of large droplets. The numerical simulation of this process suggests that the formation of large 30–40-μm droplets may occur within 20–30 min inside a shallow adiabatic stratiform layer. The dependencies of the rate of the droplet size distribution broadening on the intensity of the vertical fluctuations, their spatial amplitude, rate of mixing, droplet concentration, and other parameters are considered here. The effectiveness of this mechanism in different types of clouds is discussed.

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Condensational and Collisional Growth of Cloud Droplets in a Turbulent Environment

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-19-0107.1 ◽

2019 ◽

Vol 77 (1) ◽

pp. 337-353 ◽

Cited By ~ 2

Author(s):

Xiang-Yu Li ◽

Axel Brandenburg ◽

Gunilla Svensson ◽

Nils E. L. Haugen ◽

Bernhard Mehlig ◽

...

Keyword(s):

Size Distribution ◽

Droplet Size ◽

Early Stage ◽

Droplet Size Distribution ◽

Energy Dissipation Rate ◽

Cloud Droplets ◽

Navier Stokes Equation ◽

Droplet Dynamics ◽

Condensational Growth ◽

Rain Formation

Abstract We investigate the effect of turbulence on the combined condensational and collisional growth of cloud droplets by means of high-resolution direct numerical simulations of turbulence and a superparticle approximation for droplet dynamics and collisions. The droplets are subject to turbulence as well as gravity, and their collision and coalescence efficiencies are taken to be unity. We solve the thermodynamic equations governing temperature, water vapor mixing ratio, and the resulting supersaturation fields together with the Navier–Stokes equation. We find that the droplet size distribution broadens with increasing Reynolds number and/or mean energy dissipation rate. Turbulence affects the condensational growth directly through supersaturation fluctuations, and it influences collisional growth indirectly through condensation. Our simulations show for the first time that, in the absence of the mean updraft cooling, supersaturation-fluctuation-induced broadening of droplet size distributions enhances the collisional growth. This is contrary to classical (nonturbulent) condensational growth, which leads to a growing mean droplet size, but a narrower droplet size distribution. Our findings, instead, show that condensational growth facilitates collisional growth by broadening the size distribution in the tails at an early stage of rain formation. With increasing Reynolds numbers, evaporation becomes stronger. This counteracts the broadening effect due to condensation at late stages of rain formation. Our conclusions are consistent with results of laboratory experiments and field observations, and show that supersaturation fluctuations are important for precipitation.

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