HR: 13:45h
AN: A33E-01 INVITED     [Abstracts]
TI: Ice particle collision electrification in mixed phase cloud.
AU: Saunders, C
EM: clive.saunders@manchester.ac.uk
AF: School of Earth, Atmospheric and Environmental Sciences, The University of Manchester Sackville Street, Manchester, M60 1QD United Kingdom
AU: * Hallett, J
EM: hallett@dri.edu
AF: Desert Research Institute , 2215 Raggio Parkway, Reno, NV 89512-1095 United States
AB: Over the last 50 years, laboratory experiments have demonstrated the dependence and complexity of ice particle electrification following particle impact and bounce from actively riming simulated graupel particles. Results showed dependence on temperature, liquid water content, particle size, and impact velocity as well as the effect of trace impurity. In these experiments, the relative concentration of ice and water has been provided in different ways for simulating the growth environment, leading to questions about the most appropriate situation in the atmosphere to apply the results. In early experiments, particle growth was simulated in ice and supercooled cloud, well mixed mechanically. In more recent experiments, the environment has been provided by forming the ice and water cloud separately until quasi-equilibrium is reached and bringing the clouds together to be mixed a few seconds prior to impact on the growth particle. This may be accomplished in turbulent or laminar flow depending on the system size and velocity chosen. Thus results are to be compared with differing scales of bringing together of ice and supercooled cloud flows in the atmosphere (as in a convective or a stratiform system) and the decay of large cloud scale motions having ice or water mixed on a variety of scales as the cloud size turbulent motions decay to smaller turbulent and ultimately laminar eddies. These considerations predicate the utility of experiments already carried out and suggest new experiments under different conditions to seek results which up to now have been elusive.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0320 Cloud physics and chemistry
DE: 3304 Atmospheric electricity
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005