Intraseasonal response of the northern Indian Ocean coastal waveguide to the Madden-Julian Oscillation - OLVAC Access content directly
Journal Articles Geophysical Research Letters Year : 2009

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

S. S. C. Shenoi
  • Function : Author
Julian P. Mccreary
  • Function : Author
D. Shankar
  • Function : Author
V. Fernando
  • Function : Author
S. R. Shetye
  • Function : Author

Abstract

A new observational record of upper-ocean currents at 15°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°N, the minimum period for planetary waves is ˜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.
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hal-00763274 , version 1 (29-10-2021)

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Jérôme Vialard, S. S. C. Shenoi, Julian P. Mccreary, D. Shankar, Fabien Durand, et al.. Intraseasonal response of the northern Indian Ocean coastal waveguide to the Madden-Julian Oscillation. Geophysical Research Letters, 2009, 36, pp.14606. ⟨10.1029/2009GL038450⟩. ⟨hal-00763274⟩
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