The Role of Ice Nuclei in the Evolution of Supercooled and Mixed-phase Clouds

OVERVIEW

Measurements of ice nuclei with the CSU CFDC instrument were made on the NCAR C-130 aircraft in the international Alliance Icing Research Study – II held in November 2003. Description of the overall goals and objectives of AIRS-2 may be found on the project web pages. A coordinated and collaborative effort focused on the study of mixed-phase cloud processes was made by a group of U.S. investigators on the C-130. These activities were funded by the National Science Foundation Division of Atmospheric Sciences . The specific grant for this research was ATM-0313628. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

GOALS

• Characterize the concentrations of ice nuclei, as a function of temperature and saturation ratio, feeding different cloud regions in winter storm scenarios.

• Analysis will focus on assessing origins of nuclei or reasons for absence of nuclei for ice formation in observed clouds; on the role of seeding from cold overlying ice layers and on the spatial distribution of the nuclei in relation to mixed phase cloud regions.

• Determine ice nuclei chemical composition to give inference to their sources.

METHODS

Note: The counterflow virtual impactor was operated by Cynthia Twohy of Oregon State University.

RESULTS

Activities (PDF)

Findings (PDF)

PUBLICATIONS

DeMott, P. J., C. H. Towhy, D. C. Rogers, S. D. Brooks and S. M. Kreidenweis, 2007: Ice formation in supercooled clouds: Dependence on the spatial distribution, physical and chemical properties of ice nuclei and other aerosol particles. In preparation for submission to J. Atmos. Sci.

DeMott, P. J., A. J. Prenni, D. C. Rogers, and S. M. Kreidenweis, 2007: Multi-study compilation of ice nuclei concentrations, physical and chemical characteristics, and their implications for numerical model parameterization development. In preparation for submission to J. Atmos. Sci.

DeMott, P. J., C. H. Twohy, A. J. Prenni, S. D. Brooks, S. M. Kreidenweis, D. C. Rogers, and M. Poellot, Ice nucleation by cloud particle residues: Chemical compositions and inferences regarding ice initiation in clouds. Eos Trans. AGU, 85(47), Fall Meet. Suppl., Abstract A51E-0845, 2004.

DeMott, P. J., C. H. Twohy, A. J. Prenni, S. M. Kreidenweis, S. D. Brooks, and D. C. Rogers, Ice nuclei variability and ice formation in mixed-phase clouds, Eos Trans. AGU, 86(52), Fall Meet. Suppl., Abstract A33E-03, 2005.

DeMott, P. J., A. J. Prenni, S. M. Kreidenweis, C. H. Twohy, and D. C. Rogers, Ice Nuclei Variability and Ice Formation in Mixed-phase Clouds, DOE-ARM Annual Science Team Meeting, Albuquerque, NM, March 27-30, 2006 (On CD-ROM).

DeMott, P. J., A. J. Prenni, M. S. Richardson, S. M. Kreidenweis, C. H. Twohy, and D. C. Rogers, Ice nuclei variability, relation to ambient aerosol properties, and impacts on mixed-phase clouds, AMS Conf. on Cloud Physics, Madison, WI, 2006 (On CD-ROM).

PHOTO GALLERY