The Global Atmospheric Electrical Circuit and Climate

Abstract

Evidence is emerging for physical links among clouds, global temperatures, the global atmospheric electrical circuit and cosmic ray ionisation. The global circuit extends throughout the atmosphere from the planetary surface to the lower layers of the ionosphere. Cosmic rays are the principal source of atmospheric ions away from the continental boundary layer: the ions formed permit a vertical conduction current to flow in the fair weather part of the global circuit. Through the (inverse) solar modulation of cosmic rays, the resulting columnar ionisation changes may allow the global circuit to convey a solar influence to meteorological phenomena of the lower atmosphere. Electrical effects on non-thunderstorm clouds have been proposed to occur via the ionassisted formation of ultrafine aerosol, which can grow to sizes able to act as cloud condensation nuclei, or through the increased ice nucleation capability of charged aerosols. Even small atmospheric electrical modulations on the aerosol size distribution can affect cloud properties and modify the radiative balance of the atmosphere, through changes communicated globally by the atmospheric electrical circuit. Despite a long history of work in related areas of geophysics, the direct and inverse relationships between the global circuit and global climate remain largely quantitatively unexplored. From reviewing atmospheric electrical measurements made over two centuries and possible paleoclimate proxies, global atmospheric electrical circuit variability should be expected on many timescales.Keywords: cloud microphysics; atmospheric aerosols; cosmic rays; climate change; solar variability; solar-terrestrial physics; global circuit; ionosphere-troposphere coupling; paleoclimate; GEOP220 2 SummaryThe atmospheric electrical circuit is modulated by variations in shower clouds and tropical thunderstorms, and generates a vertical electric field in non-thunderstorm (or fair weather) regions globally. Modulation of the fair weather electric field occurs on daily, seasonal, solar cycle and century timescales. There is a long history of atmospheric electric field measurements.Variations in the atmospheric electrical circuit have a new relevance because of empirical relationships found between cosmic ray ion production, cloud properties and global temperature. Mechanisms have been proposed linking clouds and the solar modulation of cosmic rays through the microphysics of ions, aerosols and clouds. Theories exist which explain ion-assisted aerosol particle formation and the increased capture rates of charged aerosols over neutral aerosols by cloud droplets, possibly enhancing droplet freezing. Atmospheric electrical modification of cloud properties may have significant global implications for climate, via changes in the atmospheric energy balance.Combining studies of cloud microphysics and cosmic rays with the global atmospheric electrical circuit presents a relatively unexplored area of climate science, in which progress can clearly be expected. Events such as the atmo...

The global lightning-induced nitrogen oxides source

“…Positive correlations between surface temperature, lightning activity, and the global electric circuit have been identified from observations at daily to interannual time scales (Williams, 1992;Harrison, 2004;Williams, 2005). The amplitude of the Schumann resonance oscillations in the ground-ionospheric cavity (Schumann, 1952;Rycroft et al, 2000;Price et al, 2007) and temperature fluctuations in the tropical atmosphere are positively correlated mainly because of lightning activity increasing with temperature (Williams, 1992).…”

“…(2) Assuming a discharge energy of 6.7 GJ per flash (Price et al, 1997b), a flash rate of 44 s −1 , a global discharge current of 1 kA (Donohoe et al, 1977) (the total air-Earth current is about 1.8 kA (Harrison, 2004)), and the molar mass of the respective species.…”

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

“…Techniques for measurement of air conductivity and conduction current density are not discussed further here, but summaries of the associated methods required are given in Harrison (2004), Aplin and Harrison (2001) and Bennett and Harrison (2008).…”

Multi-station synthesis of early twentieth century surface atmospheric electricity measurements for upper tropospheric properties

“…Solar activity increased during the twentieth century, and a greater change occurred in approximately the first half of the century than the second half of the century (Lockwood, 2001). Most atmospheric electricity measurements in the first half of the twentieth century were made at the surface (Harrison, 2004), but a 1909 to 1959 reduction in lower atmosphere ion production is apparent in early European balloon-carried atmospheric electricity measurements (Harrison and Bennett, 2007).…”