Numerical Study of the Effect of CCN on the Size Distribution of Cloud Droplets

Kuba, Naomi; Takeda, Takeshi

doi:10.2151/jmsj1965.61.3_375

Cited by 13 publications

(7 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our results suggest, as do others (Kuba and Takeda, 1983;Cooper et al, 1997;Feingold et al, 1999;Saleeby and Cotton, 2004), that the effects of hygroscopic seeding can vary with the background CCN number concentrations (not shown in this paper) and updraft velocity at the cloud base (or cloud types) as well as the sizes and amounts of seeding particles and the timing of seeding (not shown in this paper). Therefore, more observational data must be collected on background CCN number concentrations and cloud-base updraft velocities.…”

Section: Discussionsupporting

confidence: 84%

“…Figure 3 shows the wind field at the time of peak updraft velocity for the shallow convective cloud case (a) and the stratiform cloud case (b). Kuba and Takeda (1983), Cooper et al (1997), Feingold et al (1999), and Saleeby and Cotton (2004) showed that giant CCN have the greatest effect on the precipitation efficiency of warm rain clouds in cases with numerous small background CCN. When low concentrations of small CCN are present, adding giant CCN results in a slight decrease in rainfall, suggesting that almost all rainwater is produced by condensation onto small CCN.…”

Section: Numerical Experimentsmentioning

confidence: 98%

See 1 more Smart Citation

Effect of hygroscopic seeding on warm rain clouds – numerical study using a hybrid cloud microphysical model

Kuba

Murakami²

2010

Atmos. Chem. Phys.

View full text Add to dashboard Cite

Abstract. The effect of hygroscopic seeding on warm rain clouds was examined using a hybrid cloud microphysical model combining a Lagrangian Cloud Condensation Nuclei (CCN) activation model, a semi-Lagrangian droplet growth model, and an Eulerian spatial model for advection and sedimentation of droplets. This hybrid cloud microphysical model accurately estimated the effects of CCN on cloud microstructure and suggested the following conclusions for a moderate continental air mass (an air mass with a large number of background CCN). (1) Seeding can hasten the onset of surface rainfall and increase the accumulated amount of surface rainfall if the amount and radius of seeding particles are appropriate. (2) The optimal radius of monodisperse particles to increase rainfall becomes larger with the increase in the total mass of seeding particles. (3) Seeding with salt micro-powder can hasten the onset of surface rainfall and increase the accumulated amount of surface rainfall if the amount of seeding particles is sufficient. (4) Seeding by a hygroscopic flare decreases rainfall in the case of large updraft velocity (shallow convective cloud) and increases rainfall slightly in the case of small updraft velocity (stratiform cloud). (5) Seeding with hygroscopic flares including ultragiant particles (r>5 µm) hastens the onset of surface rainfall but may not significantly increase the accumulated surface rainfall amount. (6) Hygroscopic seeding increases surface rainfall by two kinds of effects: the "competition effect" by Correspondence to: N. Kuba (kuba@jamstec.go.jp) which large soluble particles prevent the activation of smaller particles and the "raindrop embryo effect" in which giant soluble particles can immediately become raindrop embryos. In some cases, one of the effects works, and in other cases, both effects work, depending on the updraft velocity and the amount and size of seeding particles.

show abstract

Section: Discussionsupporting

confidence: 84%

Section: Numerical Experimentsmentioning

confidence: 98%

Effect of hygroscopic seeding on warm rain clouds – numerical study using a hybrid cloud microphysical model

Kuba

Murakami²

2010

Atmos. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…The cloud parcel model used in this study has been explained elsewhere [Takeda and Kuba, 1982;Kuba and Takeda, 1983;Kuba et al, 2003]. Here the calculation scheme has been modified from the previous versions by calculating the growth and activation of particles by κ-Köhler theory.…”

Section: Cloud Parcel Modelmentioning

confidence: 99%

Assessment of cloud condensation nucleus activation of urban aerosol particles with different hygroscopicity and the application to the cloud parcel model

Kawana

Kuba

Mochida

2014

J. Geophys. Res. Atmos.

Self Cite

View full text Add to dashboard Cite

Size-resolved measurements of the ratios of cloud condensation nuclei (CCN) to condensation nuclei for particles with different hygroscopic growth factors (g) and distributions of g at 85% relative humidity were performed for urban aerosols over Nagoya, Japan. The CCN efficiency spectra of less hygroscopic particles (g of 1.0 and 1.1) were very different from those of more hygroscopic particles (g of 1.25 and 1.4). While the differences between the CCN activation diameters predicted from g (d act,g85 ) and those measured (d act,CCN ) were within 12% for more hygroscopic particles, the differences were larger (16%-41%) for less hygroscopic particles. Possible causes of this included surface tension reduction, the dependence of κ on the concentration of the solution, the existence of sparingly soluble materials, and asphericity of particles. The number concentrations of CCN (N CCN ) and cloud droplets (N cd ) and the effective radius of cloud droplets (R eff ) were estimated from the distributions of g using a cloud parcel model. The influences of the differences between d act,g85 and d act,CCN and the existence of CCN-inactive particles on the model assessment were small. With high updraft velocity, incorporating both less and more hygroscopic particles into the model led to substantial increases in N CCN and N cd and a decrease in R eff as compared to the hypothetical cases that only more hygroscopic particles were present. The results indicated that less hygroscopic particles significantly contribute to cloud droplet formation and assessments of g distributions are useful in this regard.

show abstract

“…Moreover, this will be a key technique for understanding the rainout mechanisms of pollutants and optical properties of clouds. In addition, information about the size distribution of cloud droplets is an important factor for estimating the precipitation efficiency of clouds and the chemical composition of rain (Kuba and Takeda, 1983).…”

Section: Introductionmentioning

confidence: 99%

Preliminary Study on the Visualization and Quantification of Elemental Compositions in Individual Microdroplets using Solidification and Synchrotron Radiation Techniques

Ma¹,

Tohno²,

Kasahara³

2011

Asian J. Atmos. Environ

View full text Add to dashboard Cite

Quantifying the solute composition of a cloud droplet (or a whole droplet) is an important task for understanding formation processes and heating/cooling rates. In this study, a combination of droplet fixation and SR-XRF microprobe analysis was used to visualize and quantify elements in a micro-scale droplet. In this study, we report the preliminary outcome of this experiment. A spherical micro-scale droplet was successfully solidified through exposure to α-cyanoacrylate vapor without affecting its size or shape. An X-ray microprobe system equipped at the beam line 37XU of Super Photon ring 8 GeV (SPring-8) was applied to visualize and quantify the elemental composition in an individual micro-scale droplet. It was possible to reconstruct 2D elemental maps for the K and Cl contained in a microdroplet that was dispensed from the 10-ppm KCl standard solution. Multi-elemental peaks corresponding to X-ray energy were also successfully resolved. Further experiments to determine quantitative measures of elemental mass in individual droplets and high-resolution Xray microtomography (i.e., 3D elemental distribution) are planned for the future.

show abstract

Numerical Study of the Effect of CCN on the Size Distribution of Cloud Droplets

Cited by 13 publications

References 15 publications

Effect of hygroscopic seeding on warm rain clouds – numerical study using a hybrid cloud microphysical model

Effect of hygroscopic seeding on warm rain clouds – numerical study using a hybrid cloud microphysical model

Assessment of cloud condensation nucleus activation of urban aerosol particles with different hygroscopicity and the application to the cloud parcel model

Preliminary Study on the Visualization and Quantification of Elemental Compositions in Individual Microdroplets using Solidification and Synchrotron Radiation Techniques

Contact Info

Product

Resources

About