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Yanai waves in the western equatorial Indian Ocean

DRS at CSIR-National Institute of Oceanography

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Title Yanai waves in the western equatorial Indian Ocean
 
Creator Chatterjee, A.
Shankar, D.
McCreary, J.P.
Vinayachandran, P.N.
 
Subject equatorial dynamics
instability
energy
water waves
 
Description Observations and models have shown the presence of intraseasonal fluctuations in 20-30-day and 10-20-day bands in the equatorial Indian Ocean west of 60 degrees E (WEIO). Their spatial and temporal structures characterize them as Yanai waves, which we label low-frequency (LFYW) and high-frequency (HFYW) Yanai waves, respectively. We explore the dynamics of these intraseasonal signals, using an ocean general circulation model (Modular Ocean Model) and a linear, continuously stratified model. Yanai waves are forced by the meridional wind tau sup(y) everywhere in the WEIO most strongly during the monsoon seasons. They are forced both directly in the interior ocean and by reflection of the interior response from the western boundary; interference between the interior and boundary responses results in a complex surface pattern that propagates eastward and has nodes. Yanai waves are also forced by instabilities primarily during June/July in a region offshore from the western boundary (52-55 degrees E). At that time, eddies, generated by barotropic instability of the Southern Gyre, are advected southward to the equator. There, they generate a westward-propagating, cross-equatorial flow field, v sub(eq), with a wave number/frequency spectrum that fits the dispersion relation of a number of Yanai waves, and these waves are efficiently excited. Typically, Yanai waves associated with several baroclinic modes are excited by both wind and eddy forcing; and typically, they superpose to create beams that carry energy vertically and eastward along ray paths. The same processes generate LFYWs and HFYWs, and hence, their responses are similar; differences are traceable to the property that HFYWs have longer wavelengths than LFYWs for each baroclinic mode.
 
Date 2013-04-25T12:09:38Z
2013-04-25T12:09:38Z
2013
 
Type Journal Article
 
Identifier Journal of Geophysical Research: Oceans, vol.118; 2013; 15pp., 20121
no
http://drs.nio.org/drs/handle/2264/4289
 
Language en
 
Relation J_Geophys_Res_C_Oceans_118_20121.jpg
 
Rights An edited version of this paper was published by AGU. Copyright [2013] AGU. To view the published open abstract, go to http://dx.doi.org/10.1002/jgrc.20121
 
Publisher American Geophysical Union