Aerosol and Clouds
Ice iron/sodium film as cause for high noctilucent cloud radar reflectivity
Article first published online: 26 AUG 2008
Copyright 2008 by the American Geophysical Union.
Journal of Geophysical Research: Atmospheres (1984–2012)
Volume 113, Issue D16, 27 August 2008
How to Cite
2008), Ice iron/sodium film as cause for high noctilucent cloud radar reflectivity, J. Geophys. Res., 113, D16215, doi:10.1029/2008JD009927.(
- Issue published online: 26 AUG 2008
- Article first published online: 26 AUG 2008
- Manuscript Accepted: 12 JUN 2008
- Manuscript Revised: 30 APR 2008
- Manuscript Received: 6 FEB 2008
- Noctilucent cloud;
- sodium/iron layer
 Noctilucent clouds, tiny cold electrically charged ice grains located at about 85 km altitude, exhibit anomalously high radar reflectivity. It is shown that this observed high radar reflectivity can be explained by assuming the ice grains are coated by a thin metal film; substantial evidence exists indicating that such a film exists and is caused by the deposition of iron and sodium atoms on the ice grain from iron and sodium layers located immediately above the noctilucent cloud layer. The number of conduction electrons in the thin metal film coating an ice grain is very large. When averaged over the volume occupied by a large number of ice grains, the quivering of these metal film electrons provides a much larger contribution to radar reflectivity than does the much smaller number of dusty plasma electrons or electron holes. Using observations indicating that noctilucent clouds are the dominant sink for the summer-time iron and sodium layers, it is shown that a sufficiently thick metal layer should form on a typical ice grain in a few hours to a few days.