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Observational evidence of lower-frequency Yanai waves in the central equatorial Indian Ocean

DRS at CSIR-National Institute of Oceanography

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Title Observational evidence of lower-frequency Yanai waves in the central equatorial Indian Ocean
 
Creator David, D.T.
PrasannaKumar, S.
Byju, P.
Sarma, M.S.S.
Suryanarayana, A.
Murty, V.S.N.
 
Subject Indian Ocean Dipole
positive IOD
sea level anomaly
long time series data
 
Description Analysis of long time series of current meter data from a mooring at 77 degrees E and the equator during 2003–2007, along with mean sea level anomaly data, throws light on the occurrence of the lower-frequency (24 to 40 day) Yanai waves in the upper water column of the central equatorial Indian Ocean (EIO) during the positive Indian Ocean dipole (IOD) years of 2003, 2004, 2006, and 2007 and its absence during the negative IOD year 2005. This result is in contrast with the earlier studies that observed only the higher-frequency (biweekly period) Yanai wave in this region. We propose a new notion for the generation of the lower-frequency Yanai wave in the upper central EIO owing to the positive IOD phenomenon. The strong meridional current shear created by the northward shifting and strengthening of the westward flowing south equatorial current associated with positive IOD and the eastward flowing southwest monsoon current provides energy for the generation of lower-frequency Yanai waves. Vertical stratification of the water column appears to be responsible for the trapping of the different frequency of Yanai waves, with only the higher-frequency Yanai wave in the region of lower pycnocline. During positive IOD the strongly stratified upper water column responds to the lower-frequency Yanai wave, while the deeper ocean (4000 m) exhibited a longer-period (47 day) oscillation. The expected surface signature of Madden-Julian oscillation seems to be suppressed by strong easterlies during the positive IOD years.
 
Date 2011-07-07T11:44:54Z
2011-07-07T11:44:54Z
2011
 
Type Journal Article
 
Identifier Journal of Geophysical Research. C: Oceans, vol.116(6); 2011; doi:10.1029/2010JC006603, 17p.
http://drs.nio.org/drs/handle/2264/3876
 
Language en
 
Rights An edited version of this paper was published by AGU. Copyright [2010] AGU. To view the published open abstract, go to http://dx.doi.org/10.1029/2010JC006603
 
Publisher American Geophysical Union