Determining the time constant of the global atmospheric electric circuit through modelling and observations

Rycroft, M. J., Odzimek, A. and Harrison, R. G. ORCID: https://orcid.org/0000-0003-0693-347X (2024) Determining the time constant of the global atmospheric electric circuit through modelling and observations. Journal of Atmospheric and Solar-Terrestrial Physics, 260. 106267. ISSN 1879-1824 doi: 10.1016/j.jastp.2024.106267

Abstract/Summary

The DC global electric circuit (GEC) distributes charge in the lower atmosphere by current flow between “generator regions” (thunderstorms and rain clouds) and “load regions” (distant conductive air), with a timescale defined by circuit properties. Previously, the load has only been modelled by assuming fair weather (FW) conditions, neglecting cloud. As stratiform clouds cover 30 % of the Earth’s surface, load resistance has been added to represent them, considered to provide semi fair weather (semi-FW) conditions. This increases the GEC timescale by 9 % for stratocumulus, or 33 % for stratus at a lower level. Including mutual capacitance between the outer charged layer and an electrode representing stratocumulus clouds increases the timescale by 35 %, to 8.6 minutes. These modelled results - the first including the semi-FW aspects - are demonstrated to be consistent with experimentally determined timescales of the real GEC, of between 7 and 12 minutes, derived from volcanic lightning variations associated with the May 2011 Grímsvötn eruption in Iceland. Accounting for semi-FW circumstances improves the modelled representation of the natural global circuit. Further, the GEC timescale is comparable with cloud droplet charging timescales in the updrafts of extensive layer clouds, suggesting its possible relevance to the microphysical behaviour of stratiform (layer) clouds in the climate system.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/116654
Identification Number/DOI	10.1016/j.jastp.2024.106267
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Elsevier
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