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GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L14111, doi:10.1029/2004GL020465, 2004

Aircraft measurements of high average charges on cloud drops in layer clouds

Kenneth V. Beard

Department of Atmospheric Sciences, University of Illinois, Urbana-Champaign, Illinois, USA


Harry T. Ochs III

Department of Atmospheric Sciences, University of Illinois, Urbana-Champaign, Illinois, USA


Cynthia H. Twohy

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA


Abstract

The first reliable aircraft measurements of characteristic cloud drop charges were obtained by utilizing a counterflow virtual impactor to substantially increase charge sensitivity and eliminate spurious contact charging that contaminated previous aircraft measurements. We find average drop charges more than an order of magnitude larger than expected from mountain surface measurements in similar clouds. Our evaluation of the data indicates that the high average charges on cloud drops originate in charge layers at the cloud boundaries and are carried into the cloud layer by vertical motions. These initial aircraft results demonstrate that cloud drop charges in layer clouds may be high enough to influence microphysical processes that promote precipitation.

Received 6 May 2004; accepted 6 July 2004; published 31 July 2004.

Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 0394 Atmospheric Composition and Structure: Instruments and techniques.

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Citation: Beard, K. V., H. T. Ochs III, and C. H. Twohy (2004), Aircraft measurements of high average charges on cloud drops in layer clouds, Geophys. Res. Lett., 31, L14111, doi:10.1029/2004GL020465.