On the effective aerodynamic and scalar roughness length of Weddell Sea ice

Abstract

We study the effective aerodynamic roughness length z 0 and scalar roughness length for temperature z T -eff over different compact sea ice types in the Antarctic Weddell Sea by aircraft measurements during two austral summer seasons. z 0 and z T are highly variable in the Weddell Sea ice area. The averaged value of T in all main sea ice areas was smaller than the averaged value of z0. The ratio between the two roughness lengths was relatively small for new/young sea ice with z 0 z T 2, but the ratio became significantly large for the multiyear pack ice with z 0 z T 227. For the pack ice area, with sea ice concentration ranging between 95% to 100%, we determined a median z 0 = 4.1 × 10 -03 m and a median z T = 1.8 × 10 -05 m. In the new, young sea ice area, with sea ice concentration ranging between 98% and 100%, we observed a median z 0 = × 10 -04 m and a median z T = 2.2 × 10 -04 m. These values of z 0 and z T differ from published observations conducted in a pack ice and new, young sea ice area in the northern hemisphere, such as the Arctic. Most model parameterizations require the roughness lengths as constant values as boundary input parameters. Our study shows that by using the z 0 and z T values of this study, instead of commonly used sea ice roughness length values, the accuracy of parameterized heat and momentum fluxes in the Weddell Sea ice area can significantly be improved. Copyright 2011 by the American Geophysical Union.