Geometric and aerodynamic roughness of sea ice

✍ Scribed by S. Mai; C. Wamser; C. Kottmeier

• Publisher: Springer
• Year: 1996
• Tongue: English
• Weight: 821 KB
• Volume: 77
• Category: Article
• ISSN: 0006-8314
• DOI: 10.1007/bf00123526

✦ Synopsis

The aerodynamic drag of Arctic sea ice is calculated using surface data, measured by an airborne laser altimeter and a digital camera in the marginal ice zone of Fram Strait. The influence of the surface morphology on the momentum transfer under neutral thermal stratification in the atmospheric boundary layer is derived with the aid of model concepts, based on the partitioning of the surface drag into a form drag and a skin drag. The drag partitioning concept pays attention to the probability density functions of the geometric surface parameters. We found for the marginal ice zone that the form drag, caused by floe edges, can amount to 140% of the skin drag, while the effect of pressure ridges never exceeded 40%. Due to the narrow spacing of obstacles, the skin drag is significantly reduced by shadowing effects on the leeward side of floe edges. For practical purposes, the fractional sea-ice coverage can be used to parameter&e the drag coefficient Cdn, related to the 10 m-wind. Cdn increases from 1.2. 10e3 over open water to 2.8 t 10V3 for 55% ice coverage and decreases to 1.5 . 10m3 for 100% ice coverage.

Aircraft turbulence measurements are used to compare the model values of Cdn with measurements. The correlation between measured and modelled drag coefficients results in r2 = 0.9 1, where r is the correlation coefficient.