Atmos. Chem. Phys. Discuss., 8, 17691-17737, 2008
www.atmos-chem-phys-discuss.net/8/17691/2008/
doi:10.5194/acpd-8-17691-2008
© Author(s) 2008. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Large surface radiative forcing from surface-based ice crystal events measured in the High Arctic at Eureka
G. Lesins1, L. Bourdages1, T. J. Duck1, J. R. Drummond1, E. W. Eloranta2, and V. P. Walden3
1Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada
2Space Science and Engineering Center, University of Wisconsin, Madison, USA
3Department of Geography, University of Idaho, Moscow, ID, USA

Abstract. Ice crystals, also known as diamond dust, are suspended in the boundary layer air under clear sky conditions during most of the Arctic winter in Northern Canada. Occasionally ice crystal events can produce significantly thick layers with optical depths in excess of 2.0 even in the absence of liquid water clouds. Four case studies of high optical depth ice crystal events at Eureka in the Nunavut Territory of Canada during the winter of 2006–2007 are presented. They show that the measured ice crystal surface infrared downward radiative forcing ranged from 8 to 36 W m−2 in the wavelength band from 5.6 to 20 μm for visible optical depths ranging from 0.2 to 1.7. MODIS infrared and visible images and the operational radiosonde wind profile were used to show that these high optical depth events were caused by surface snow being blown off 600 to 800 m high mountain ridges about 20 to 30 km North-West of Eureka and advected by the winds towards Eureka as they settled towards the ground within the highly stable boundary layer. This work presents the first study that demonstrates the important role that surrounding topography plays in determining the occurrence of high optical depth ice crystal events and points to a new source of boundary layer ice crystal events distinct from the classical diamond dust phenomenon.

Citation: Lesins, G., Bourdages, L., Duck, T. J., Drummond, J. R., Eloranta, E. W., and Walden, V. P.: Large surface radiative forcing from surface-based ice crystal events measured in the High Arctic at Eureka, Atmos. Chem. Phys. Discuss., 8, 17691-17737, doi:10.5194/acpd-8-17691-2008, 2008.
 
Search ACPD
Discussion Paper
    XML
    Citation
    Final Revised Paper
    Share