scholarly journals Equilibrium Radius of Cloud Droplets Competitively Grown on Cloud Condensation Nuclei Containing Water-Insoluble Dust

2004 ◽  
Vol 12 ◽  
pp. 247-252
Author(s):  
Sadataka SHIBA ◽  
Yushi HIRATA ◽  
Shunsaku YAGI
Keyword(s):  
Cloud Condensation Nuclei ◽  
Condensation Nuclei ◽  
Cloud Droplets ◽  
Equilibrium Radius

scholarly journals Estimation of cloud condensation nuclei number concentrations and comparison to in situ and lidar observations during the HOPE experiments

2020 ◽  
Vol 20 (14) ◽  
pp. 8787-8806 ◽  
Author(s):  
Christa Genz ◽  
Roland Schrödner ◽  
Bernd Heinold ◽  
Silvia Henning ◽  
Holger Baars ◽  
...  
Keyword(s):  
Ammonium Nitrate ◽  
Ammonium Sulfate ◽  
Cloud Condensation Nuclei ◽  
Chemical Species ◽  
Ground Level ◽  
Radiative Properties ◽  
Condensation Nuclei ◽  
Cloud Droplets ◽  
Sensitivity Studies

Abstract. Atmospheric aerosol particles are the precondition for the formation of cloud droplets and therefore have large influence on the microphysical and radiative properties of clouds. In this work, four different methods to derive or measure number concentrations of cloud condensation nuclei (CCN) were analyzed and compared for present-day aerosol conditions: (i) a model parameterization based on simulated particle concentrations, (ii) the same parameterization based on gravimetrical particle measurements, (iii) direct CCN measurements with a CCN counter, and (iv) lidar-derived and in situ measured vertical CCN profiles. In order to allow for sensitivity studies of the anthropogenic impact, a scenario to estimate the maximum CCN concentration under peak aerosol conditions of the mid-1980s in Europe was developed as well. In general, the simulations are in good agreement with the observations. At ground level, average values between 0.7 and 1.5×109 CCN m−3 at a supersaturation of 0.2 % were found with the different methods under present-day conditions. The discrimination of the chemical species revealed an almost equal contribution of ammonium sulfate and ammonium nitrate to the total number of CCN for present-day conditions. This was not the case for the peak aerosol scenario, in which it was assumed that no ammonium nitrate was formed while large amounts of sulfate were present, consuming all available ammonia during ammonium sulfate formation. The CCN number concentration at five different supersaturation values has been compared to the measurements. The discrepancies between model and in situ observations were lowest for the lowest (0.1 %) and highest supersaturations (0.7 %). For supersaturations between 0.3 % and 0.5 %, the model overestimated the potentially activated particle fraction by around 30 %. By comparing the simulation with observed profiles, the vertical distribution of the CCN concentration was found to be overestimated by up to a factor of 2 in the boundary layer. The analysis of the modern (year 2013) and the peak aerosol scenario (expected to be representative of the mid-1980s over Europe) resulted in a scaling factor, which was defined as the quotient of the average vertical profile of the peak aerosol and present-day CCN concentration. This factor was found to be around 2 close to the ground, increasing to around 3.5 between 2 and 5 km and approaching 1 (i.e., no difference between present-day and peak aerosol conditions) with further increasing height.

scholarly journals Relationships between particles, cloud condensation nuclei and cloud droplet activation during the third Pallas Cloud Experiment

2012 ◽  
Vol 12 (6) ◽  
pp. 13691-13732
Author(s):  
T. Anttila ◽  
D. Brus ◽  
A. Jaatinen ◽  
A.-P. Hyvärinen ◽  
N. Kivekäs ◽  
...  
Keyword(s):  
Size Distribution ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Droplet Surface ◽  
The Arctic ◽  
Condensation Nuclei ◽  
Cloud Droplets ◽  
The Third ◽  
Droplet Activation ◽  
Experimental Values

Abstract. Concurrent measurement of aerosols, cloud condensation nuclei (CCN) and cloud droplet activation were carried out as a part of the third Pallas Cloud Experiment (PaCE-3) which took place at a ground based site located on northern Finland during the autumn of 2009. In this study, we investigate relationships between the aerosol properties, CCN and size resolved cloud droplet activation. During the investigated cloudy periods, the inferred number of cloud droplets (CDNC) varied typically between 50 and 150 cm−3 and displayed a linear correlation both with the number of particles having sizes over 100 nm and with the CCN concentrations at 0.4% supersaturation. Furthermore, the diameter corresponding to the 50% activation fraction, D50, was generally in the range of 80 to 120 nm. The measured CCN concentrations were compared with predictions of a numerical model which used the measured size distribution and size resolved hygroscopicity as input. Assuming that the droplet surface tension is equal to that of water, the measured and predicted CCN concentrations were generally within 30%. We also simulated size dependent cloud droplet activation with a previously developed air parcel model. By forcing the model to reproduce the experimental values of CDNC, adiabatic estimates for the updraft velocity and the maximum supersaturation reached in the clouds were derived. Performed sensitivity studies showed further that the observed variability in CDNC was driven mainly by changes in the particle size distribution while the variations in the updraft velocity and hygroscopicity contributed to a lesser extent. The results of the study corroborate conclusions of previous studies according to which the number of cloud droplets formed in clean air masses close to the Arctic is determined mainly by the number of available CCN.

scholarly journals Relationships between particles, cloud condensation nuclei and cloud droplet activation during the third Pallas Cloud Experiment

2012 ◽  
Vol 12 (23) ◽  
pp. 11435-11450 ◽  
Author(s):  
T. Anttila ◽  
D. Brus ◽  
A. Jaatinen ◽  
A.-P. Hyvärinen ◽  
N. Kivekäs ◽  
...  
Keyword(s):  
Size Distribution ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Droplet Surface ◽  
The Arctic ◽  
Condensation Nuclei ◽  
Cloud Droplets ◽  
The Third ◽  
Droplet Activation ◽  
Experimental Values

Abstract. Concurrent measurement of aerosols, cloud condensation nuclei (CCN) and cloud droplet activation were carried out as a part of the third Pallas Cloud Experiment (PaCE-3) which took place at a ground based site located on northern Finland during the autumn of 2009. In this study, we investigate relationships between the aerosol properties, CCN and size resolved cloud droplet activation. During the investigated cloudy periods, the inferred number of cloud droplets (CDNC) varied typically between 50 and 150 cm−3 and displayed a linear correlation both with the number of particles having sizes over 100 nm and with the CCN concentrations at 0.4% supersaturation. Furthermore, the diameter corresponding to the 50% activation fraction, D50, was generally in the range of 80 to 120 nm. The measured CCN concentrations were compared with predictions of a numerical model which used the measured size distribution and size resolved hygroscopicity as input. Assuming that the droplet surface tension is equal to that of water, the measured and predicted CCN concentrations were generally within 30%. We also simulated size dependent cloud droplet activation with a previously developed air parcel model. By forcing the model to reproduce the experimental values of CDNC, adiabatic estimates for the updraft velocity and the maximum supersaturation reached in the clouds were derived. Performed sensitivity studies showed further that the observed variability in CDNC was driven mainly by changes in the particle size distribution while the variations in the updraft velocity and hygroscopicity contributed to a lesser extent. The results of the study corroborate conclusions of previous studies according to which the number of cloud droplets formed in clean air masses close to the Arctic is determined mainly by the number of available CCN.

scholarly journals Regional New Particle Formation as Modulators of Cloud Condensation Nuclei and Cloud Droplet Number in the Eastern Mediterranean

2018 ◽  
Author(s):  
Panayiotis Kalkavouras ◽  
Aikaterini Bougiatioti ◽  
Nikos Kalivitis ◽  
Maria Tombrou ◽  
Athanasios Nenes ◽  
...  
Keyword(s):  
Gas Phase ◽  
Particle Number ◽  
Eastern Mediterranean ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Significant Fraction ◽  
Size Distributions ◽  
Condensation Nuclei ◽  
Cloud Droplets ◽  
Condensational Growth

Abstract. A significant fraction of atmospheric particles that serve as cloud condensation nuclei (CCN), and furthermore as cloud droplets are thought to originate from the condensational growth of new particles formed from the gas phase. Here, particle number size distributions (

scholarly journals Chinese SO<sub>2</sub> pollution over Europe – Part 2: Simulation of aerosol and cloud condensation nuclei formation

2009 ◽  
Vol 9 (1) ◽  
pp. 2763-2790 ◽  
Author(s):  
V. Fiedler ◽  
F. Arnold ◽  
H. Schlager ◽  
L. Pirjola
Keyword(s):  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Fossil Fuel Combustion ◽  
Condensation Nuclei ◽  
East Atlantic ◽  
Cloud Droplets ◽  
Chinese Origin ◽  
Range Transport ◽  
Research Aircraft ◽  
Vapor Supersaturation

Abstract. We report on sulfur dioxide (SO2) induced formation of aerosols and cloud condensation nuclei in an SO2 rich aged (9 days) pollution plume of Chinese origin, which we have detected at 5–7 km altitude during a research aircraft mission over the East Atlantic off the West coast of Ireland. Building on our measurements of SO2 and other trace gases along with plume trajectory simulations, we have performed model simulations of SO2 induced formation of gaseous sulfuric acid (GSA, H2SO4) followed by GSA induced formation and growth of aerosol particles. We find that efficient photochemical SO2 conversion to GSA took place in the plume followed by efficient formation and growth of H2SO4-H2O aerosol particles. Most particles reached sufficiently large sizes to act as cloud condensation nuclei whenever water vapor supersaturation exceeded 0.1–0.2%. As a consequence, smaller but more numerous cloud droplets are formed, which tend to increase the cloud albedo and to decrease the rainout efficiency. The detected plume represents an interesting example of the environmental impact of long range transport of fossil fuel combustion generated SO2.

scholarly journals Ultraclean Layers and Optically Thin Clouds in the Stratocumulus-to-Cumulus Transition. Part II: Depletion of Cloud Droplets and Cloud Condensation Nuclei through Collision–Coalescence

2018 ◽  
Vol 75 (5) ◽  
pp. 1653-1673 ◽  
Author(s):  
Kuan-Ting O ◽  
Robert Wood ◽  
Christopher S. Bretherton
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Liquid Water Content ◽  
Cloud Base ◽  
Condensation Nuclei ◽  
Cloud Droplets ◽  
Droplet Concentration ◽  
Cloud Thickness

In Part I, aircraft observations are used to show that ultraclean layers (UCLs) in the marine boundary layer (MBL) are a common feature of the stratocumulus-to-cumulus transition (SCT) region over the northeast Pacific. The ultraclean layers are defined as layers of either cloud or clear air in which the concentration of particles with diameter larger than 0.1 μm is below 10 cm−3. Here, idealized microphysical parcel modeling shows that in the cumulus regime, collision–coalescence can strongly deplete cloud droplet concentration in cumulus (Cu) updrafts, thereby removing cloud condensation nuclei (CCN) from the atmosphere, suggesting that collision scavenging is likely the key process causing the low particle concentration in UCLs. Furthermore, the model results suggest that the stratocumulus regime is typically not favorable for UCL formation, because condensate amounts are generally not large enough to deplete drops in the time it takes to loft air to the upper planetary boundary layer (PBL). A bulk parameterization of the coalescence-scavenging rate is derived based on in situ measurements. The fractional coalescence-scavenging rate is found to be strongly dependent upon liquid water content (LWC) and, hence, the height above cloud base, indicating that a higher cloud top and thus a greater cloud thickness in a Cu updraft is an important factor accounting for the observed sharp rise of UCL coverage in the SCT region. An important implication is that PBL height, which controls maximum cloud thickness, and therefore LWC in updrafts, could be a crucial factor constraining coalescence scavenging and thus the formation of UCLs in the MBL.

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