Ocean-atmosphere momentum coupling in the Kuroshio Extension observed from space
- 128 Downloads
Using a combination of Quick Scatterometer (QuikSCAT), Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E), and Lagrangian drifter measurements, we demonstrate that wind data alone are not sufficient to derive ocean surface stress (momentum flux) over mid-latitude ocean fronts, specifically the Kuroshio Extension. There was no continuous and large-scale stress measurement over ocean until the launch of the scatterometers. Stress had been derived from winds through a drag coefficient, and our concept of stress distribution may be largely influenced by our knowledge of wind distribution. QuikSCAT reveals that the variability of stress could be very different from wind. The spatial coherence between the magnitude of stress and sea surface temperature (SST), between the divergence of surface stress and the downwind SST gradient, and between the vorticity of stress and crosswind SST gradient, are the inherent characteristics of stress (turbulence production by buoyancy) that would exist even under a uniform wind field. The coherence between stress vorticity and SST gradient is masked by the rotation of ocean currents over the Kuroshio meanders. Surface stress rotates in the opposite direction to surface currents because stress is the vector difference between wind and current. The results are in agreement with a previous study of the Agulhas Extension and confirm the unique stress measuring capability of the scatterometer.
KeywordsWind-stress ocean-front buoyancy current-shear scatterometer ocean-atmosphere-coupling divergence vorticity
Unable to display preview. Download preview PDF.
- Chelton, D. B., S. K. Esbensen, M. G. Schlax, N. Thum, M. H. Freilich, F. J. Wentz, C. L. Gentemann, M. J. McPhaden and P. S. Schoff (2001): Observations of coupling between surface wind stress and sea surface temperature in the eastern tropical Pacific. J. Climate, 14, 1479–1498.CrossRefGoogle Scholar
- Liu, W. T. and W. Tang (1996): Equivalent Neutral Wind. JPL Pub., 96-17, Jet Propulsion Lab., Pasadena, 8 pp.Google Scholar
- Liu, W. T., W. Tang and X. Xie (2008): Wind power distribution over global oceans. Geophys. Res. Lett. (submitted).Google Scholar
- Niiler, P. P. (2001): The world ocean surface circulation. p. 193–204. In Ocean Circulation and Climate—Observing and Modeling the Global Ocean, ed. by G. Siedler, J. Church and J. Gould, Academic Press, Volume 77 of International Geophysics Series.Google Scholar
- Wentz, F. J. and T. Meissner (1999): AMSR Ocean Algorithm, Version 2. RSS Tech. Report 121599A, Remote Sensing Systems.Google Scholar