Atmospheric Electricity and Cloud Microphysics
نویسنده
چکیده
The terrestrial atmospheric electrical system covers a range of dimensional scales, from charged molecular clusters to convective cloud systems. Charge-exchange associated with thunderclouds leads to positive charge in the upper conductive regions of the atmosphere and a net negative charge on the planetary surface. In non-thunderstorm regions, a vertical ionic current flows, replenishing the air with molecular ions otherwise removed by attachment, recombination or nucleation processes. Ions may have indirect effects on non-thunderstorm clouds, and therefore conceivably on climate, via cloud microphysical processes. Cloud Condensation Nuclei (CCN) and Ice Nuclei (IN) are necessary for the formation of water clouds and freezing of ice clouds respectively. In both cases, ionisation may be important: it is now known that ultrafine aerosol can be formed from ionisation, probably providing an additional source of CCN. It is also known that electrified aerosol, perhaps active as IN, can be collected by droplets more effectively than neutral particles.
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