Vertical current flow through extensive layer clouds

Nicoll, Keri; Harrison, Richard G.

doi:10.1016/j.jastp.2009.09.011

Cited by 31 publications

(25 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is a consequence of Gauss's Law applied vertically to the sharp change in air conductivity in the transition from clear air to cloudy air: in steady state, the vertical current density on both sides of the boundary is the same and so the electric field is greater on the lower conductivity side of the boundary, requiring a space charge to reside on the boundary, referred to as the 'traffic jam' effect (Chalmers 1967). Recent experimental analyses have confirmed these theoretical expectations, both in that the current density does pass through cloud layers (Nicoll & Harrison 2009) and, quantitatively, that the layer cloud charge measured using balloon-carried instrumentation is consistent with predicted values (Nicoll & Harrison 2010). A response in cloud properties to conduction current changes, for example resulting from charge effects on the formation of small water droplets containing negligible dissolved salt (Harrison & Ambaum 2008), may therefore occur at cloud edges.…”

Section: Introductionmentioning

confidence: 92%

Cloud base height and cosmic rays

2011

View full text Add to dashboard Cite

Cosmic rays modify current flow in the global atmospheric electrical circuit. Charging at horizontal layer cloud edges has been observed to be consistent with global circuit vertical current flow through the cloud, which can modify the properties of small and pure water droplets. Studies have been hampered by the absence of cloud edge observations, hence cloud base height information is investigated here. Cloud base height measured at the Lerwick Observatory, Shetland, UK, is analysed using threshold tests and spectral analysis. The cloud base height distributions for low cloud (cloud base less than 800 m) are found to vary with cosmic ray conditions. Further, 27 day and 1.68 year periodicities characteristic of cosmic ray variations are present, weakly, in the cloud base height data of stratiform clouds, when such periodicities are present in neutron monitor cosmic ray data. These features support the idea of propagation of heliospheric variability into layer clouds, through the global atmospheric electric circuit.

show abstract

Section: Introductionmentioning

confidence: 92%

Cloud base height and cosmic rays

2011

View full text Add to dashboard Cite

show abstract

“…As we have noted above, all the mechanisms work at the boundaries of super-cooled and liquid clouds. Direct experimental evidence for a link between atmospheric electricity and cloud microphysics were obtained by Harrison and Ambaum (2009) as well as Nicoll and Harrison (2009). It should be considered also that the global circuit is dependent on atmospheric column resistance, which, in turn is influenced not only by ionization but also by concentration of sulfate aerosol in the stratosphere, concentration of cosmic dust in upper atmosphere and, probably other factors.…”

Section: Cosmic Ray Flux and Terrestrial Climatementioning

confidence: 96%

Solar Activity, Space Weather and the Earth’s Climate

Ogurtsov¹,

Lindholm²,

Jalkanen³

2012

Climate Variability - Some Aspects, Challenges and Prospects

View full text Add to dashboard Cite

“…Surprisingly, the model shows areas of higher column resistance in areas of high cloud coverage, yet the global resistance is smaller than from ISCCP, driven by the areas of little cloud coverage, i.e., small column resistance. The only available measurements of air-to-earth current density depending on cloud coverage were presented by Nicoll and Harrison (2009). The authors found little change in the current density measurements, only fully overcast conditions with thick clouds led to current density reductions.…”

Section: Global Effectmentioning

confidence: 99%

“…As previously shown by Zhou and Tinsley (2010), the conductivity reduction inside a cloud can be approximated by a fraction η of ambient conductivity. Estimates for η range from 1/10 (Nicoll and Harrison, 2009) to 1/50 (Zhou and Tinsley, 2010).…”

Section: Single Cloudsmentioning

confidence: 99%

“…5. Nicoll and Harrison (2009) presented air-to-earth current density measurements from two sites in the UK, together with solar radiation measurements, and showed that current density below the cloud can be reduced, depending on cloud height and cloud thickness. Space charge development at the boundaries of clouds in the fair weather part of the GEC has been addressed by Zhou and Tinsley (2007), using model simulations, whereas a discussion of measurements of cloud edge charging from balloon flights has been presented by Nicoll and Harrison (2010).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the role of clouds in the fair weather part of the global electric circuit

Baumgaertner

Lucas²,

Thayer³

et al. 2014

Atmos. Chem. Phys.

View full text Add to dashboard Cite

Abstract. Clouds in the fair weather return path of the global electric circuit (GEC) reduce conductivity because of the limited mobility of charge due to attachment to cloud water droplets, effectively leading to a loss of ions. A highresolution GEC model, which numerically solves the current continuity equation in combination with Ohm's law, is used to show that return currents partially flow around clouds, with current divergence above the cloud and convergence below the cloud. An analysis of this effect is presented for various types of clouds, i.e., for different altitude extents and for different horizontal dimensions, finding that the effect is most pronounced for high clouds with a diameter below 100 km. Based on these results, a method to calculate column and global resistance is developed that can account for all cloud sizes and altitudes. The CESM1(WACCM) (Community Earth System Model -Whole Atmosphere Community Climate Model) as well as ISCCP (International Satellite Cloud Climatology Project) cloud data are used to calculate the effect of this phenomenon on global resistance. From CESM1(WACCM), it is found that when including clouds in the estimate of resistance the global resistance increases by up to 73 %, depending on the parameters used. Using ISCCP cloud cover leads to an even larger increase, which is likely to be overestimated because of time averaging of cloud cover. Neglecting current divergence/convergence around small clouds overestimates global resistance by up to 20 % whereas the method introduced by previous studies underestimates global resistance by up to 40 %. For global GEC models, a conductivity parameterization is developed to account for the current divergence/convergence phenomenon around clouds. Conductivity simulations from CESM1(WACCM) using this parameterization are presented.

show abstract

Vertical current flow through extensive layer clouds

Cited by 31 publications

References 22 publications

Cloud base height and cosmic rays

Cloud base height and cosmic rays

Solar Activity, Space Weather and the Earth’s Climate

On the role of clouds in the fair weather part of the global electric circuit

Contact Info

Product

Resources

About