On the size dependence of the chemical properties of cloud droplets: Exploratory studies by aircraft

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7018012

Twohy, C H

Clouds play an important role in the climate of the earth and in the transport and transformation of chemical species. The chemical properties of droplets may vary with droplet size, with potentially important consequences. The counterflow virtual impactor (CVI) separates droplets from interstitial particles and gases in a cloud and also can collect droplets in discrete size ranges. The CVI is a useful tool for investigating the chemical components present in droplets of different sizes and their potential interactions with cloud processes. The purpose of this work is twofold. First, the sampling characteristics of the airborne CVI are investigated, using data from a variety of experiments. Although the impaction characteristics of the CVI seem to be predictable by theory, the airborne instrument is subject to influences that may result in a reduced transmission efficiency for droplets, particularly if the inlet is not properly aligned. Ways to alleviate this problem are being investigated. Relationships between the physical and chemical properties of residual particles from droplets collected by the CVI and droplet size are then explored in both stratiform and cumulus clouds. The effects of various cloud processes and measurement limitations upon these relationships are discussed. In one study, chemical analysis of different-sized droplets sampled in stratiform clouds showed a dependence of chemical composition on droplet size, with larger droplets containing higher proportions of sodium than non-sea-salt sulfate and ammonium. Larger droplets were also associated with larger residual particles. In a study of marine cumulus clouds, the CVI was combined with a cloud condensation nucleus spectrometer to study the supersaturation of the droplet residual particles was consistently less than or equal to the median critical supersaturation of ambient particles except at cloud top, where residual particles exhibited a variety of critical supersaturations.

• Research Organization: Washington Univ., Seattle, WA (United States)
• OSTI ID: 7018012
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540120* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (1990-)
AERIAL MONITORING
ATMOSPHERIC CHEMISTRY
CHEMICAL PROPERTIES
CHEMISTRY
CLOUDS
CONDENSATION NUCLEI
METEOROLOGY
MONITORING
PARTICLE SIZE
SIZE