Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 5 2008 10.5194/acpd-8-17691-2008 http://www.atmos-chem-phys-discuss.net/8/17691/2008/ http://www.atmos-chem-phys-discuss.net/8/17691/2008/acpd-8-17691-2008.html http://www.atmos-chem-phys-discuss.net/8/17691/2008/acpd-8-17691-2008.pdf 17691 17737 2008-09-29 Large surface radiative forcing from surface-based ice crystal events measured in the High Arctic at Eureka G. Lesins glen.lesins@dal.ca L. Bourdages T. J. Duck J. R. Drummond E. W. Eloranta V. P. Walden Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada Space Science and Engineering Center, University of Wisconsin, Madison, USA Department of Geography, University of Idaho, Moscow, ID, USA 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. Blanchet, J.-P. and Girard, E.: Water-vapor temperature feedback in the formation of continental arctic air: implications for climate, Sci. Total Environ., 160/161, 793–802, 1995. Chen, W.-N., Chiang, C.-W., and Nee, J.-B.: Lidar ratio and depolarization ratio for cirrus clouds, Appl. Optics, 41, 6470–6476, 2002. Curry, J. A., Rossow, W. B., Randall, D., and Schramm, J. L.: Overview of arctic cloud and radiation characteristics, J. Climate, 9, 1731–1764, 1996. Ellingson, R. G. and Wiscombe, W. J.: The spectral radiance experiment (SPECTRE): Project description and sample results, B. Am. Meteorol. Soc., 77, 1967–1985, 1996. Eloranta, E. E.: High spectral resolution lidar, in: Lidar: range-resolved optical remote sensing of the atmosphere, edited by: Weitkamp, C., Springer, Singapore, 143–163, 2005. Girard, E. and Blanchet, J.-P.: Microphysical parameterization of arctic diamond dust, ice fog and thin stratus for climate models, J. Atmos. Sci., 58, 1181–1198, 2001a. Girard, E. and Blanchet, J.-P.: Simulation of arctic diamond dust and ice fog and thin stratus using an explicit aerosol-cloud-radiation model, J. Atmos. Sci., 58, 1199–1221, 2001b. Intrieri, J. M., Shupe, M. D., Uttal, T., and McCarty, B. J.: An annual cycle of Arctic cloud characteristics observed by radar and lidar at SHEBA, J. Geophys. Res., 107, 8030, doi:10.1029/2000JC000423, 2002. Intrieri, J. M. and Shupe, M. D.: Characteristics and radiative effects of diamond dust over the western Arctic Ocean region, J. Climate, 17, 2953–2960, 2004. Knuteson, R. O., Best, F. A., Ciganovich, N. C., Dedecker, R. G., Dirkx, T. P., Ellington, S., Feltz, W. F., Garcia, R. K., Herbsleb, R. A., Howell, H. B., Revercomb, H. E., Smith, W. L., and Short, J. F.: Atmospheric Emitted Radiance Interferometer (AERI): Part I: Instrument Design, J. Atmos. Ocean. Tech., 21, 1763–1776, 2004a. Knuteson, R. O., Best, F. A., Ciganovich, N. C., Dedecker, R. G., Dirkx, T. P., Ellington, S., Feltz, W. F., Garcia, R. K., Herbsleb, R. A., Howell, H. B., Revercomb, H. E., Smith, W. L., and Short, J. F.: Atmospheric Emitted Radiance Interferometer (AERI): Part II: Instrument Performance, J. Atmos. Ocean. Tech., 21, 1777–1789, 2004b. MANOBS: Manual of Surface Weather Observations, 7th Edition, Amendment No. 15, Meteorological Service of Canada, Toronto, Canada, 374 pp., 2006. Mishchenko, M. I. and Hovenier, J. W.: Depolarization of light backscattered by randomly oriented nonspherical particles, Opt. Lett., 20, 1356–1358, 1995. Overland, J. E. and Guest, P. S.: The Arctic snow and air temperature budget over sea ice during winter, J. Geophys. Res., 96, 4651–4662, 1991. Ricchiazzi, P., Yang, S., Gautier, C., and Sowle, D.: SBDART: A research and teaching software tool for plane-parallel radiative transfer in the Earth's atmosphere, B. Am. Meteorol. Soc., 79, 2101–2114, 1998. Sakai, T., Nagai, T., Nakazato, M., Mano, Y., and Matsumura, T.: Ice clouds and Asian dust studied with lidar measurements of particle extinction-to-backscatter ratio, particle depolarization, and water-vapor mixing ratio over Tsukuba, Appl. Optics, 42, 7103–7116, 2003. Savelyev, S. A., Gordon, M., Hanesiak, J., Papakyriakou, T., and Taylor, P. A.: Blowing snow studies in the Canadian Arctic Shelf Exchange Study, 2003-04, Hydrol. Process., 20, 817–827, 2006. Uttal, T., Curry, J. A., McPhee, M. G., Perovich, D. K., et al.: The surface heat budget of the Arctic Ocean, B. Am. Meteorol. Soc., 83, 255–275, 2002. Walden, V. P., Town, M. S., Halter, B., and Storey, J. W. V.: First measurements of the infrared sky brightness at Dome C, Antarctica, Proc. Pac. Astron. Soc., 117, 300–308, 2005. Walden, V. P., Roth, W. L., Stone, R. S., and Halter, B.: Radiometric validation of the Atmospheric Infrared Sounder over the Antarctic Plateau, J. Geophys. Res., 111, D09S03, doi:10.1029/2005JD006357, 2006. Witt, H. J.: Airborne observations of cloud particles and infrared flux density in the Arctic, MSc. Thesis, Department of Atmospheric Sciences, University of Washington, USA, 1968. Yang, P., Wei, H., Huang, H.-L., Baum, B. A., Hu, Y. X., Kattawar, G. W., Mishchenko, M. I., and Fu, Q.: Scattering and absorption property database for nonspherical ice particles in the near- through far-infrared spectral region, Appl. Optics, 44, 5512–5523, 2005.