The influence of Langmuir turbulence on the scaling for the dissipation rate in the oceanic boundary layer

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Teixeira, MAC (Author) Other

Journal

Title: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS

Vol. 117

ISSN: 2169-9275

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 14 Citations

Scopus - 14 Citations

Other information

Authenticus ID: P-002-A4C

DOI: 10.1029/2011jc007235

Abstract (EN): A model for estimating the turbulent kinetic energy dissipation rate in the oceanic boundary layer, based on insights from rapid-distortion theory, is presented and tested. This model provides a possible explanation for the very high dissipation levels found by numerous authors near the surface. It is conceived that turbulence, injected into the water by breaking waves, is subsequently amplified due to its distortion by the mean shear of the wind-induced current and straining by the Stokes drift of surface waves. The partition of the turbulent shear stress into a shear-induced part and a wave-induced part is taken into account. In this picture, dissipation enhancement results from the same mechanism responsible for Langmuir circulations. Apart from a dimensionless depth and an eddy turn-over time, the dimensionless dissipation rate depends on the wave slope and wave age, which may be encapsulated in the turbulent Langmuir number La-t. For large La-t, or any La-t but large depth, the dissipation rate tends to the usual surface layer scaling, whereas when Lat is small, it is strongly enhanced near the surface, growing asymptotically as epsilon (proportional to) La-t(-2) when Lat(t) -> 0. Results from this model are compared with observations from the WAVES and SWADE data sets, assuming that this is the dominant dissipation mechanism acting in the ocean surface layer and statistical measures of the corresponding fit indicate a substantial improvement over previous theoretical models. Comparisons are also carried out against more recent measurements, showing good order-of-magnitude agreement, even when shallow-water effects are important.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 15