Parameterizing Turbulent Exchange over Sea Ice in Winter
Author
Andreas, Edgar L.
Persson, P. Ola G.
Jordan, Rachel E.
Horst, Thomas W.
Guest, Peter S.
Grachev, Andrey A.
Fairall, Christopher W.
Date
2010-02Metadata
Show full item recordAbstract
The Surface Heat Budget of the Arctic Ocean (SHEBA) experiment produced 18 000 h of turbulence data
from the atmospheric surface layer over sea ice while the ice camp drifted for a year in the Beaufort Gyre.
Multiple sites instrumented during SHEBA suggest only two aerodynamic seasons over sea ice. In ‘‘winter’’
(October 1997 through 14 May 1998 and 15 September 1998 through the end of the SHEBA deployment in
early October 1998), the ice was compact and snow covered, and the snow was dry enough to drift and blow. In
‘‘summer’’ (15 May through 14 September 1998 in this dataset), the snow melted, and melt ponds and leads
appeared and covered as much as 40% of the surface with open water. This paper develops a bulk turbulent
flux algorithm to explain the winter data. This algorithm predicts the surface fluxes of momentum, and
sensible and latent heat from more readily measured or modeled quantities. A main result of the analysis is
that the roughness length for wind speed z0 does not depend on the friction velocity u* in the drifting snow
regime (u* $ 0.30 m s21) but, rather, is constant in the SHEBA dataset at about 2.3 3 1024 m. Previous
analyses that found z0 to increase with u* during drifting snow may have suffered from fictitious correlation
because u* also appears in z0. The present analysis mitigates this fictitious correlation by plotting measured z0
against the corresponding u* computed from the bulk flux algorithm. Such plots, created with data from six
different SHEBA sites, show z0 to be independent of the bulk u* for 0.15 , u* # 0.65 m s21. This study also
evaluates the roughness lengths for temperature zT and humidity zQ, incorporates new profile stratification
corrections for stable stratification, addresses the singularities that often occur in iterative flux algorithms in
very light winds, and includes an extensive analysis of whether atmospheric stratification affects z0, zT, and zQ.
Description
The article of record as published may be located at http://dx.doi.org/10.1175/2009JHM1102.1
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.Collections
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