Atmos. Chem. Phys., 7, 6161-6173, 2007
www.atmos-chem-phys.net/7/6161/2007/
doi:10.5194/acp-7-6161-2007
© Author(s) 2007. This work is licensed under the
Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
Alignment of atmospheric mineral dust due to electric field
Z. Ulanowski1, J. Bailey2, P. W. Lucas1, J. H. Hough1, and E. Hirst1
1Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB, UK
2Australian Centre for Astrobiology, Macquarie University, Sydney NSW 2109, Australia

Abstract. Optical polarimetry observations on La Palma, Canary Islands, during a Saharan dust episode show dichroic extinction indicating the presence of vertically aligned particles in the atmosphere. Modelling of the extinction together with particle orientation indicates that the alignment could have been due to an electric field of the order of 2 kV/m. Two alternative mechanisms for the origin of the field are examined: the effect of reduced atmospheric conductivity and charging of the dust layer, the latter effect being a more likely candidate. It is concluded that partial alignment may be a common feature of Saharan dust layers. The modelling indicates that the alignment can significantly alter dust optical depth. This "Venetian blind effect" may have decreased optical thickness in the vertical direction by as much as 10% for the case reported here. It is also possible that the alignment and the electric field modify dust transport.

Citation: Ulanowski, Z., Bailey, J., Lucas, P. W., Hough, J. H., and Hirst, E.: Alignment of atmospheric mineral dust due to electric field, Atmos. Chem. Phys., 7, 6161-6173, doi:10.5194/acp-7-6161-2007, 2007.
 
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