scholarly journals Technical note: Characterization of a static thermal-gradient CCN counter

2006 ◽  
Vol 6 (2) ◽  
pp. 2151-2174 ◽  
Author(s):  
G. P. Frank ◽  
U. Dusek ◽  
M. O. Andreae
Keyword(s):  
Water Vapor ◽  
Thermal Gradient ◽  
Cloud Condensation Nuclei ◽  
Diffusion Chamber ◽  
Calibration Method ◽  
Theoretical Description ◽  
Technical Note ◽  
Number Concentration ◽  
Gradient Diffusion

Abstract. The static (parallel-plate thermal-gradient) diffusion chamber (SDC) was one of the first instruments designed to measure cloud condensation nuclei (CCN) concentrations as a function of supersaturation. It has probably also been the most widely used type of CCN counter. This paper describes the detailed experimental characterization of a SDC CCN counter, including calibration with respect to supersaturation and particle number concentration. In addition, we investigated the proposed effect of lowered supersaturation because of water vapor depletion with increasing particle concentration. The results obtained gives a larger understanding why and in which way it is necessary to calibrate the SDC CCN counter. The calibration method is described in detail as well. The method can, in parts, be used for calibrations also for other types of CCN counters. We conclude the following: 1) it is important to experimentally calibrate SDC CCN counters with respect to supersaturation, and not only base the supersaturation on the theoretical description of the instrument; 2) the number concentration calibration needs to be performed as a function of supersaturation, also for SDC CCN counter using the photographic technique; and 3) we observed no evidence that water vapor depletion lowered the supersaturation.

scholarly journals Technical Note: Characterization of a static thermal-gradient CCN counter

2007 ◽  
Vol 7 (12) ◽  
pp. 3071-3080 ◽  
Author(s):  
G. P. Frank ◽  
U. Dusek ◽  
M. O. Andreae
Keyword(s):  
Water Vapor ◽  
Thermal Gradient ◽  
Cloud Condensation Nuclei ◽  
Diffusion Chamber ◽  
Calibration Method ◽  
Theoretical Description ◽  
Technical Note ◽  
Number Concentration ◽  
Gradient Diffusion

Abstract. The static (parallel-plate thermal-gradient) diffusion chamber (SDC) was one of the first instruments designed to measure cloud condensation nuclei (CCN) concentrations as a function of supersaturation. It has probably also been the most widely used type of CCN counter. This paper describes the detailed experimental characterization of a SDC CCN counter, including calibration with respect to supersaturation and particle number concentration. In addition, we investigated the proposed effect of lowered supersaturation because of water vapor depletion with increasing particle concentration. The results obtained give a better understanding why and in which way it is necessary to calibrate the SDC CCN counter. The calibration method is described in detail and can, in parts, be used for calibrations also for other types of CCN counters. We conclude the following: 1) it is important to experimentally calibrate SDC CCN counters with respect to supersaturation, and not only base the supersaturation on the theoretical description of the instrument; 2) the number concentration calibration needs to be performed as a function of supersaturation, also for SDC CCN counter using the photographic technique; and 3) we observed no evidence that water vapor depletion lowered the supersaturation.

scholarly journals Organic acids as cloud condensation nuclei: Laboratory studies of highly soluble and insoluble species

2003 ◽  
Vol 3 (1) ◽  
pp. 949-982 ◽  
Author(s):  
P. Pradeep Kumar ◽  
K. Broekhuizen ◽  
J. P. D. Abbatt
Keyword(s):  
Organic Acids ◽  
Room Temperature ◽  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
Diffusion Chamber ◽  
Laboratory Studies ◽  
Condensation Nuclei ◽  
Gradient Diffusion ◽  
Kohler Theory ◽  
Good Agreement

Abstract. The ability of sub-micron-sized organic acid particles to act as cloud condensation nuclei (CCN) has been examined at room temperature using a newly constructed continuous-flow, thermal-gradient diffusion chamber (TGDC). The organic acids studied were: oxalic, malonic, glutaric, oleic and stearic. The CCN properties of the highly soluble acids – oxalic, malonic and glutaric – match very closely Kohler theory predictions which assume full dissolution of the dry particle and a surface tension of the growing droplet equal to that of water. In particular, for supersaturations between 0.3 and 0.6, agreement between the dry particle diameter which gives 50% activation and that calculated from Kohler theory is to within 3 nm on average. In the course of the experiments, considerable instability of glutaric acid particles was observed as a function of time and there is evidence that they fragment to some degree to smaller particles. Stearic acid and oleic acid, which are both highly insoluble in water, did not activate at supersaturations of 0.6% with dry diameters up to 140 nm. Finally, to validate the performance of the TGDC, we present results for the activation of ammonium sulfate particles that demonstrate good agreement with Kohler theory if solution non-ideality is considered. Our findings support earlier studies in the literature that showed highly soluble organics to be CCN active but insoluble species to be largely inactive.

scholarly journals Technical note: A method for measuring size-resolved CCN in the atmosphere

2006 ◽  
Vol 6 (3) ◽  
pp. 4879-4895 ◽  
Author(s):  
G. P. Frank ◽  
U. Dusek ◽  
M. O. Andreae
Keyword(s):  
Particle Size ◽  
Water Vapor ◽  
Size Range ◽  
Cloud Condensation Nuclei ◽  
Technical Note ◽  
Condensation Nuclei ◽  
Ambient Aerosols ◽  
Condensation Particle Counter ◽  
Set Up ◽  
Vapor Supersaturation

Abstract. We present a method to investigate cloud condensation nuclei (CCN) concentrations and activation efficiencies as a function of two independent variables, aerosol particle size and water vapor supersaturation. To date, most ambient CCN measurements have been made as the integral (total) CCN concentration as a function of water vapor supersaturation only. However, since CCN properties of aerosol particles are strongly dependent on particle size, as well as on chemical composition, which commonly varies with particle size, more detailed measurements can provide additional important information about the CCN activation. With size-resolved measurements, the effect of particle size on CCN activity can be kept constant, which makes it possible to directly assess the influence of particle chemistry. The instrumental set-up consists of a differential mobility analyzer (DMA) to select particles of a known size, within a narrow size range. A condensation nuclei (CN) counter (condensation particle counter, CPC) is used to count the total number of particles in that size range, and a CCN counter is used to count the number of CCN as a function of supersaturation, in that same size range. The activation efficiency, expressed as CCN/CN ratios, can thus directly be calculated as a function of particle size and supersaturation. We present examples of the application of this technique, using salt and smoke aerosols produced in the laboratory as well as ambient aerosols.

scholarly journals Closure between measured and modeled cloud condensation nuclei (CCN) using size-resolved aerosol compositions in downtown Toronto

2005 ◽  
Vol 5 (4) ◽  
pp. 6263-6293 ◽  
Author(s):  
K. Broekhuizen ◽  
R. Y.-W. Chang ◽  
W. R. Leaitch ◽  
S.-M. Li ◽  
J. P. D. Abbatt
Keyword(s):  
Cloud Condensation Nuclei ◽  
Compositional Analysis ◽  
Diffusion Chamber ◽  
Aerosol Size Distribution ◽  
Condensation Nuclei ◽  
Aerosol Composition ◽  
Average Value ◽  
Aerosol Mass ◽  
Gradient Diffusion ◽  
Kohler Theory

Abstract. Measurements of cloud condensation nuclei (CCN) were made in downtown Toronto during August and September, 2003. CCN measurements were performed at 0.58% supersaturation using a thermal-gradient diffusion chamber, whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and APS system and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively. Aerosol composition data shows that the particles were predominately organic in nature, in particular for those with a vacuum aerodynamic diameter of <25 μm. In this study, the largest contribution to CCN concentrations came from this size range, suggesting that the CCN are also organic-rich. Using the size and composition information, a detailed CCN closure analysis was performed. In all analyses, the particles were assumed to be internally mixed, the organic fraction was assumed to be insoluble, and the inorganic fraction was assumed to be ammonium sulfate. The AMS time-of-flight data were used for Köhler theory predictions for each particle size and composition to obtain the dry diameter required for activation. By so doing, this closure analysis yielded an average value of CCNpredicted/CCNobserved= 1.04 (R2=0.87). Several other closure analyses were performed to mimic other methods of aerosol compositional analysis. In all cases, by assuming uniform aerosol composition across a wider range of particle sizes, significant overprediction of CCN concentrations resulted.

scholarly journals Closure between measured and modeled cloud condensation nuclei (CCN) using size-resolved aerosol compositions in downtown Toronto

2006 ◽  
Vol 6 (9) ◽  
pp. 2513-2524 ◽  
Author(s):  
K. Broekhuizen ◽  
R.Y.-W. Chang ◽  
W. R. Leaitch ◽  
S.-M. Li ◽  
J. P. D. Abbatt
Keyword(s):  
Cloud Condensation Nuclei ◽  
Diffusion Chamber ◽  
Droplet Surface ◽  
Aerosol Size Distribution ◽  
Condensation Nuclei ◽  
Aerosol Composition ◽  
Average Value ◽  
Aerosol Mass ◽  
Gradient Diffusion ◽  
Kohler Theory

Abstract. Measurements of cloud condensation nuclei (CCN) were made in downtown Toronto during August and September, 2003. CCN measurements were performed at 0.58% supersaturation using a thermal-gradient diffusion chamber, whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and APS system and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively. Aerosol composition data shows that the particles were predominately organic in nature, in particular for those with a vacuum aerodynamic diameter of <0.25 µm. In this study, the largest contribution to CCN concentrations came from this size range, suggesting that the CCN are also organic-rich. Using the size and composition information, detailed CCN closure analyses were performed. In the first analysis, the particles were assumed to be internally mixed, the organic fraction was assumed to be insoluble, and the inorganic fraction was assumed to be ammonium sulfate. The AMS time-of-flight data were used for Köhler theory predictions for each particle size and composition to obtain the dry diameter required for activation. By so doing, this closure analysis yielded an average value of CCNpredicted/CCNobserved=1.12±0.05. However, several sample days showed distinct bimodal distributions, and a closure analysis was performed after decoupling the two particle modes. This analysis yielded an average value of CCNpredicted/CCNobserved=1.03±0.05. A sensitivity analysis was also performed to determine the aerosol/CCN closure if the organic solubility, droplet surface tension, or chamber supersaturation were varied.

scholarly journals Organic acids as cloud condensation nuclei: Laboratory studies of highly soluble and insoluble species

2003 ◽  
Vol 3 (3) ◽  
pp. 509-520 ◽  
Author(s):  
P. Pradeep Kumar ◽  
K. Broekhuizen ◽  
J. P. D. Abbatt
Keyword(s):  
Organic Acids ◽  
Room Temperature ◽  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
Diffusion Chamber ◽  
Laboratory Studies ◽  
Condensation Nuclei ◽  
Gradient Diffusion ◽  
Kohler Theory ◽  
Good Agreement

Abstract. The ability of sub-micron-sized organic acid particles to act as cloud condensation nuclei (CCN) has been examined at room temperature using a newly constructed continuous-flow, thermal-gradient diffusion chamber (TGDC). The organic acids studied were: oxalic, malonic, glutaric, oleic and stearic. The CCN properties of the highly soluble acids - oxalic, malonic and glutaric - match very closely Köhler theory predictions which assume full dissolution of the dry particle and a surface tension of the growing droplet equal to that of water. In particular, for supersaturations between 0.3 and 0.6, agreement between the dry particle diameter which gives 50% activation and that calculated from Köhler theory is to within 3nm on average. In the course of the experiments, considerable instability of glutaric acid particles was observed as a function of time and there is evidence that they fragment to some degree to smaller particles. Stearic acid and oleic acid, which are both highly insoluble in water, did not activate at supersaturations of 0.6% with dry diameters up to 140nm. Finally, to validate the performance of the TGDC, we present results for the activation of ammonium sulfate particles that demonstrate good agreement with Köhler theory if solution non-ideality is considered. Our findings support earlier studies in the literature that showed highly soluble organics to be CCN active but insoluble species to be largely inactive.

scholarly journals Evaluation of the contribution of new particle formation to cloud droplet number concentration in the urban atmosphere

2021 ◽  
Vol 21 (18) ◽  
pp. 14293-14308
Author(s):  
Sihui Jiang ◽  
Fang Zhang ◽  
Jingye Ren ◽  
Lu Chen ◽  
Xing Yan ◽  
...  
Keyword(s):  
Water Vapor ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Particle Formation ◽  
Number Concentration ◽  
Urban Atmosphere ◽  
New Particle Formation ◽  
High Background ◽  
Effect Of Water ◽  
Cloud Droplet Number Concentration

Abstract. The effect of new particle formation (NPF) on cloud condensation nuclei (CCN) varies widely in diverse environments. CCN or cloud droplets from NPF sources remain highly uncertain in the urban atmosphere; they are greatly affected by the high background aerosols and frequent local emissions. In this study, we quantified the effect of NPF on cloud droplet number concentration (CDNC, or Nd) at typical updraft velocities (V) in clouds based on field observations on 25 May–18 June 2017 in urban Beijing. We show that NPF increases the Nd by 32 %–40 % at V=0.3–3 m s−1 during the studied period. The Nd is reduced 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 calculated from constant supersaturations due to the water vapor competition effect, which suppresses the cloud droplet formation by decreasing the environmental maximum supersaturation (Smax). The effect of water vapor competition becomes smaller at larger V that can provide more sufficient water vapor. However, under extremely high aerosol particle number concentrations, the effect of water vapor competition becomes more pronounced. As a result, although a larger increase of CCN-sized particles by NPF events is derived on clean NPF days when the number concentration of preexisting background aerosol particles is very low, no large discrepancy is presented in the enhancement of Nd by NPF between clean and polluted NPF days. We finally reveal a considerable impact of the primary sources on the evaluation of the contribution of NPF to CCN number concentration (NCCN) and Nd based on a case study. Our study highlights the importance of full consideration of both the environmental meteorological conditions and multiple sources (i.e., secondary and primary) to evaluate the effect of NPF on clouds and the associated climate effects in polluted regions.

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