Equatorial variability and resonance in a wind-driven Indian Ocean model

Journal Article · Wed Dec 15 04:00:00 EST 1993 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/93JC02565· OSTI ID:81661

Jensen, T G ^[1]

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1. Colorado State Univ., Fort Collins, CO (United States)

A numerical isopycnal ocean model has been designed and applied to model the Indian Ocean north of 25{degrees}S. Vertical normal modes are used in the open boundary conditions and for selections of initial layer depths. A 21-year integration with a reduced Hellerman-Rosenstein monthly averaged wind stress has been made with 3.5-layer and 1.5-layer versions of the model. Both solutions reproduce the main features of the observed wind-driven seasonal circulation in the Indian Ocean above the main thermocline. The transient semiannual equatorial surface jets are more intense, more coherent, and in better phase agreement with observations when three layers are active. The associated undercurrents below the main thermocline are also included in the 3.5-layer model solution. Second baroclinic-mode, reflecting, equatorial Kelvin and Rossby waves combine to give a semiannual, resonant basin mode. Experiments with an equatorial band of semiannual zonal winds suggest a very strong response of the Indian Ocean to wind forcing with this period. Further, the amplitudes of the 28-30 day oscillations in the western equatorial model region are found to be strongly damped with depth; they have upward phase propagation and downward energy propagation. 43 refs., 22 figs., 2 tabs.

• Sponsoring Organization: USDOE
• DOE Contract Number: FG02-89ER69027; FG02-92ER61440
• OSTI ID: 81661
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: C12 Vol. 98; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
INDIAN OCEAN
NUMERICAL ANALYSIS
OCEANIC CIRCULATION
RESONANCE
WATER CURRENTS
WIND