Evidence for global circuit current flow through water droplet layers |
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| Authors: | AJ Bennett RG Harrison |
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| Institution: | 1. Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria;2. School of Chemistry, Bangor University, Bangor, United Kingdom;1. Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanova St., 603950, Nizhny Novgorod, Russia;2. Lobachevsky State University of Nizhny Novgorod, 23 Gagarina Ave., 603950, Nizhny Novgorod, Russia;1. School of Earth and Space Sciences, Peking University, Bejing 100871, China;2. Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China;3. State Key Laboratory of Enhanced oil Recovery, Beijing 100083, China;1. Dept of Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7, Canada;2. Centre for Planetary Science and Exploration, University of Western Ontario, London, Ontario, N6A 5B7, Canada;3. Ann and H. J. Smead Department of Aerospace Engineering Sciences, University of Colorado Boulder, Colorado, 80303, USA |
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| Abstract: | Foggy air and clear air have appreciably different electrical conductivities. The conductivity gradient at horizontal droplet boundaries causes droplet charging, as a result of vertical current flow in the global atmospheric electrical circuit. The charging is poorly known, as both the current flow through atmospheric water droplet layers and the air conductivity are poorly characterised experimentally. Surface measurements during three days of continuous fog using new instrument techniques show that a shallow (of order 100 m deep) fog layer still permits the vertical conduction current to pass. Further, the conductivity in the fog is estimated to be approximately 20% lower than in clear air. Assuming a fog transition thickness of one metre, this implies a vertical conductivity gradient of order 10 fS m?2 at the boundary. The actual vertical conductivity gradient at a cloud boundary would probably be greater, due to the presence of larger droplets in clouds compared to fog, and cleaner, more conductive clear air aloft. |
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