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Title: QuikSCAT-based momentum flux analysis over the Southern Ocean
Authors: Luis, Alvarinho J.
Ravindra, Rasik
Keywords: Southern Ocean
QuikSCAT vector winds
Momentum flux
Antarctic circumpolar current
Wind stress curl
Vector winds
Issue Date: Mar-2008
Publisher: CSIR
Abstract: Using QuikSCAT vector winds, the seasonal and interannual variability of momentum flux were studied to explore the underlining dynamics for its modulation over the Southern Ocean (SO) during August 1999 to July 2003. The wind speed validation of ship and QuikSCAT measurements in the western Indian sector of the SO showed a bias and root mean square error of 0.3 and 1.6 m/s, respectively. On seasonal time scales, the spatial wind stress patterns reveal a basin-wide variability and the boreal summer monsoon significantly influencing it in the Indian Ocean (IO) sector. The temporal march of the momentum flux for different ocean sectors exhibit a seasonal cycle with a maximum range between 0.13 and 0.18 N/m2 during August-September and a minimum range between 0.07 and 0.11 N/m2 during December – January, with a temporal shift of ±1 month between the sectors. The atmospheric pressure gradient between tropics and high latitudes enhances the momentum flux in the IO sector during austral winter. On interannual time scales the momentum flux maps indicate a marked regional variability which is highest in IO sector and an evolution of cyclonic circulation south of 50°S during austral winter. Based on earlier studies and after a detailed examination of SST and wind stress curl fields, it is argued that orientation of the SST gradient relative to direction of wind stress drive an atmospheric response through wind stress curl and divergence modulations, which in turn dictates the intensity of momentum flux on seasonal time scales.
Description: 47-54
ISSN: 0379-5136
Appears in Collections:IJMS Vol.37(1) [March 2008]

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