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Intraseasonal response of the northern Indian Ocean coastal waveguide to the Madden-Julian Oscillation

DRS at CSIR-National Institute of Oceanography

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Title Intraseasonal response of the northern Indian Ocean coastal waveguide to the Madden-Julian Oscillation
 
Creator Vialard, J.
Shenoi, S.S.C.
McCreary, J.P.
Shankar, D.
Durand, F.
Fernando, V.
Shetye, S.R.
 
Subject Indian Ocean
coastal waveguide
Kelvin waves
intraseasonal energy
 
Description A new observational record of upper-ocean currents at 15 degrees N on the western coast of India is dominated by intraseasonal (55-110 day) variations of alongshore currents, whereas sea level at the same location has a clear seasonal signal. These observations can be interpreted within the framework of linear wave theory. At 15 degrees N, the minimum period for planetary waves is approx. 90 day, meaning that intraseasonal energy is largely trapped at the coast in the form of poleward-propagating Kelvin waves, while lower-frequency signals associated with the annual cycle can radiate offshore as planetary waves. This dynamical difference results in a steeper offshore slope of sea level at intraseasonal timescale, and thus stronger geostrophic alongshore currents. A consequence is that the alongshore currents are in-phase with intraseasonally-filtered sea level near the coast, and a gridded satellite product is shown to reproduce the current variations reasonably well. The intraseasonal current variations along the west coast of India are part of basin-scale sea-level fluctuations of the Northern Indian Ocean equatorial and coastal waveguides. The wind forcing associated with this basin scale circulation closely matches surface wind signals associated with the Madden-Julian Oscillation.
 
Date 2009-11-17T11:52:00Z
2009-11-17T11:52:00Z
2009
 
Type Journal Article
 
Identifier Geophysical Research Letters, vol.36(14); 2009; doi:10.1029/2009GL038450; 5 pp
http://drs.nio.org/drs/handle/2264/3449
 
Language en
 
Rights An edited version of this paper was published by AGU. Copyright [2009] AGU. To view the published open abstract, go to http://dx.doi.org and enter the DOI.
 
Publisher American Geophysical Union