Cloud base height and cosmic rays
Harrison, R. G., Ambaum, M. P. H. and Lockwood, M. (2011) Cloud base height and cosmic rays. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 467 (2134). pp. 2777-2791. ISSN 1471-2946
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To link to this article DOI: 10.1098/rspa.2011.0040
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.