通过建模和观测确定全球大气电路的时间常数

IF 1.8 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
Michael J. Rycroft , Anna Odzimek , R. Giles Harrison
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引用次数: 0

摘要

直流全球电路(GEC)通过 "发电机区域"(雷暴和雨云)和 "负载区域"(远处的导电空气)之间的电流在低层大气中分布电荷,其时间尺度由电路特性确定。以前,只在假设天气晴朗(FW)的条件下模拟负载,忽略了云层。由于层状云覆盖了地球表面的 30%,因此增加了负载电阻来代表它们,以提供半晴朗天气(semi-FW)条件。这将使层积云的 GEC 时间尺度增加 9%,或使较低层的层云的 GEC 时间尺度增加 33%。如果将带电外层与代表层积云的电极之间的相互电容计算在内,则时间尺度将增加 35%,达到 8.6 分钟。这些模拟结果--第一个包括半风向的模拟结果--被证明与根据 2011 年 5 月冰岛 Grímsvötn 火山喷发相关的火山闪电变化得出的实际 GEC 时间尺度一致,即介于 7 至 12 分钟之间。考虑到半闪电的情况,改进了对全球自然回路的模拟表示。此外,GEC 时间尺度与大范围层云上升气流中的云滴充电时间尺度相当,表明它可能与气候系统中层状(层)云的微物理行为有关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Determining the time constant of the global atmospheric electric circuit through modelling and observations

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 min. 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 min, 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.

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来源期刊
Journal of Atmospheric and Solar-Terrestrial Physics
Journal of Atmospheric and Solar-Terrestrial Physics 地学-地球化学与地球物理
CiteScore
4.10
自引率
5.30%
发文量
95
审稿时长
6 months
期刊介绍: The Journal of Atmospheric and Solar-Terrestrial Physics (JASTP) is an international journal concerned with the inter-disciplinary science of the Earth''s atmospheric and space environment, especially the highly varied and highly variable physical phenomena that occur in this natural laboratory and the processes that couple them. The journal covers the physical processes operating in the troposphere, stratosphere, mesosphere, thermosphere, ionosphere, magnetosphere, the Sun, interplanetary medium, and heliosphere. Phenomena occurring in other "spheres", solar influences on climate, and supporting laboratory measurements are also considered. The journal deals especially with the coupling between the different regions. Solar flares, coronal mass ejections, and other energetic events on the Sun create interesting and important perturbations in the near-Earth space environment. The physics of such "space weather" is central to the Journal of Atmospheric and Solar-Terrestrial Physics and the journal welcomes papers that lead in the direction of a predictive understanding of the coupled system. Regarding the upper atmosphere, the subjects of aeronomy, geomagnetism and geoelectricity, auroral phenomena, radio wave propagation, and plasma instabilities, are examples within the broad field of solar-terrestrial physics which emphasise the energy exchange between the solar wind, the magnetospheric and ionospheric plasmas, and the neutral gas. In the lower atmosphere, topics covered range from mesoscale to global scale dynamics, to atmospheric electricity, lightning and its effects, and to anthropogenic changes.
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