Article
 

Measurements of Cloud Condensation Nuclei Spectra within Maritime Cumulus Cloud Droplets: Implications for Mixing Processes

Public Deposited

Downloadable Content

Download PDF
https://ir.library.oregonstate.edu/concern/articles/9593tw69f

Descriptions

Attribute NameValues
Creator
Abstract
  • In a cloud formed during adiabatic expansion, the droplet size distribution will be systematically related to the critical supersaturation of the cloud condensation nuclei (CCN), but this relationship can be complicated in entraining clouds. Useful information about cloud processes, such as mixing, can be obtained from direct measurements of the CCN involved in droplet nucleation. This was accomplished by interfacing two instruments for a series of flights in maritime cumulus clouds. One instrument, the counterflow virtual impactor, collected cloud droplets, and the nonvolatile residual nuclei of the droplets was then passed to a CCN spectrometer, which measured the critical supersaturation (S[subscript]c) spectrum of the droplet nuclei. The measured S[subscript]c spectra of the droplet nuclei were compared with the Sc spectra of ambient aerosol particles in order to identify which CCN were actually incorporated into droplets and to determine when mixing processes were active at different cloud levels. The droplet nuclei nearly always exhibited lower median S[subscript]c's than the ambient aerosol, as expected since droplets nucleate preferentially on particles with lower critical supersaturations. Critical supersaturation spectra from nuclei of droplets near cloud base were similar to those predicted for cloud regions formed adiabatically, but spectra of droplet nuclei from middle cloud levels showed some evidence that mixing had occurred. Near cloud top, the greatest variation in the spectra of the droplet nuclei was observed, and nuclei with high S[subscript]c's were sometimes present even within relatively large droplets. This suggests that the extent of mixing increases with height in cumulus clouds and that inhomogeneous mixing may be important near cloud top. These promising initial results suggest improvements to the experimental technique that will permit more quantitative results in future experiments.
Resource Type
DOI
Date Available
Date Issued
Citation
  • Twohy, Cynthia H., James G. Hudson, 1995: Measurements of Cloud Condensation Nuclei Spectra within Maritime Cumulus Cloud Droplets: Implications for Mixing Processes. Journal of Applied Meteorology, 34, 815–833.
Journal Title
Journal Volume
  • 34
Journal Issue/Number
  • 4
Rights Statement
Funding Statement (additional comments about funding)
  • The NCAR Advanced Studies Program, as well as NASA through Cooperative Agreement ATM-9209181, provided funding for C. Twohy. J. Hudson was supported by ONR N00014-91-J-1090 and NSF ATM 8919935.
Publisher
Language
Replaces

Relationships

Parents:

This work has no parents.

Items

Thumbnail Title Date Uploaded Visibility Actions
file details TwohyCynthiaH.CEOAS.MeasurementsCloudCondensation.pdf 2017-07-24 Public Download