Extended Abstract (2.4M)7.1
Determining wintertime heterogeneous pack ice characteristics and their impact on the aggregate atmospheric surface fluxes
P. O. G. Persson, CIRES/Univ. of Colorado, NOAA/ETL, Boulder, CO; and E. L. Andreas, J. -. W. Bao, C. W. Fairall, A. A. Grachev, P. S. Guest, and R. E. Jordan
During the Surface heat Budget of the Arctic Ocean (SHEBA) field program in 1997-1998, detailed measurements of near-surface temperatures, momentum flux, sensible and latent heat fluxes, radiation, and basic meteorological parameters, including precipitation, were made at the main SHEBA site and 3 remote stations. In addition, extensive in-situ measurements were made of the evolution of the snow and ice thickness at several locations. Satellite remote sensing measurements were also made of the surface ice type from synthetic aperture radar (SAR) and of the surface temperature distribution from AVHRR. Surface remote sensing was used to obtain measurements of the cloud macrostructure (cloud base, top, cloud fraction) and precipitation. All of these observations are combined as input to a 1-D snow and ice model with parameterized surface heat flux and forced by observed basic atmospheric variables to estimate the spatial distribution of the snow and ice thickness and the associated surface temperature during a mostly clear-sky week in January. The thickness distributions are shown to be in acceptable agreement with observations, and the resultant surface temperature distribution during clear sky conditions is validated with AVHRR satellite data. The 1-D ice/snow model then provides the spatial distribution of surface temperature estimates during both cloudy and clear conditions. In a 100 X 100 km region centered on the main SHEBA site, the spatial variation of surface temperature can be greater than 10°C due to large meso-beta-scale areas of relatively thin ice, with temperatures over the thinner ice significantly warmer than the temperatures of -35°C observed over the multi-year pack ice at the main SHEBA site. The spatial distribution of the surface fluxes can then be estimated from the recent Grachev et al (2004) bulk flux algorithm, allowing the computation of GCM-scale surface fluxes. A 3-D simulation is also run using the MM5 with a 1 X 1 km fine-mesh resolution and a snow/ice module permitting spatially varying snow and ice thickness. This simulation provides a likely improved estimate of the GCM-scale surface fluxes by permitting mesoscale boundary-layer circulations to develop and horizontal advection to affect the fluxes over the heterogeneous surface.
Session 7, Atmospheric/Sea-Ice/Ocean Exchanges
Wednesday, 12 January 2005, 8:30 AM-9:30 AM
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