5a.4
The air-ice drag coefficient measured for a year over Arctic sea ice
Edgar L Andreas, U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, NH; and C. W. Fairall, P. S. Guest, and O. P. G. Persson
During SHEBA, the experiment to study the Surface Heat Budget of the Arctic Ocean, we measured the air-ice drag coefficient by both eddy-correlation and profile analysis on a 20-m tower in the main camp and by eddy-correlation at four remote sites within 1-10 km of the main camp. From the eddy-correlation measurements in the main camp alone, we have over 4000 hourly averaged estimates of the neutral-stability drag coefficient for a reference height of 10 meters, CDN10. Monthly averages of these CDN10 values show a gradual increase from 1.1x10-3 in November 1997 to 1.5x10-3 in May 1998, probably as a consequence of ridge building. CDN10 increases more steeply in June, July, and August to its August 1998 annual peak of 1.9x10-3 as melt ponds formed and grew in spatial extent. In September 1998, CDN10 began decreasing as snow filled in the now-frozen melt ponds and, thus, smoothed the ice surface. We will look for corroboration of this trend in CDN10 values from the four remote sites but will also use these data, collected over various ice types, to try to understand the distribution of CDN10 values that went into constituting the monthly averages. In other words, we will explore ways to predict and parameterize the individual CDN10 values.
Session 5a, Atmosphere-Surface Exchanges and Forcings (Parallel with Session 5B)
Friday, 18 May 2001, 8:00 AM-10:00 AM
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