On the microphysical effects of observed cloud edge charging

Harrison, R. G. ORCID: https://orcid.org/0000-0003-0693-347X, Nicoll, K. A. ORCID: https://orcid.org/0000-0001-5580-6325 and Ambaum, M. H. P. ORCID: https://orcid.org/0000-0002-6824-8083 (2015) On the microphysical effects of observed cloud edge charging. Quarterly Journal of the Royal Meteorological Society, 141 (692). pp. 2690-2699. ISSN 1477-870X doi: 10.1002/qj.2554 (Part A)

Abstract/Summary

Liquid layer clouds are abundant globally. Lacking strong convection, they do not become electrified by the usual thunderstorm mechanisms of collisional electrification between hydrometeors of different phases. Instead, the background global circuit current flow in fair weather is largely unaffected by the layer cloud’s presence, and, if the layer cloud is extensive horizontally, the vertical fair weather conduction current passes through the cloud. A consequence of the vertical current flow is that, at the cloud-air boundary where there is a conductivity transition and droplets form or evaporate, droplet charging occurs. Charge can affect both droplet evaporation and droplet-droplet collisions. Using new radiosonde instrumentation, the charge observed at layer cloud edges is evaluated for both these microphysical droplet processes. This shows that the charging is more likely to affect collision processes than activation, for small droplets. Enhancing the collection efficiency of small droplets modifies their evolution and propagates through the size distribution to shorten the autoconversion timescale to rain drops, and the cloud radiative properties. Because the conduction current density is influenced by both external (e.g. solar modulation of high energy particles) and internal (e.g. ENSO) factors, current flow leading to layer cloud edge charging provides a possible route for expressing solar influences on the climate system and a teleconnection mechanism for communicating internal climate variability.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/39864
Identification Number/DOI	10.1002/qj.2554
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Royal Meteorological Society
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