Editorial Type:
Article
Article Type:
Research Article

Dynamics of the Intraseasonal Oscillations in the Indian Ocean South Equatorial Current

Lei Zhou Earth System Science Interdisciplinary Center, University of Maryland, College Park, College Park, Maryland

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Raghu Murtugudde Earth System Science Interdisciplinary Center, University of Maryland, College Park, College Park, Maryland

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Markus Jochum National Center for Atmospheric Research,* Boulder, Colorado

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Print Publication:
01 Jan 2008
DOI:
https://doi.org/10.1175/2007JPO3730.1
Page(s):
121–132
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Abstract

The spatial and temporal features of intraseasonal oscillations in the southwestern Indian Ocean are studied by analyzing model simulations for the Indo-Pacific region. The intraseasonal oscillations have periods of 40–80 days with a wavelength of ∼650 km. They originate from the southeastern Indian Ocean and propagate westward as Rossby waves with a phase speed of ∼25 cm s−1 in boreal winter and spring. The baroclinic instability is the main driver for these intraseasonal oscillations. The first baroclinic mode dominates during most of the year, but during boreal winter and spring the second mode contributes significantly and often equally. Consequently, the intraseasonal oscillations are relatively strong in boreal winter and spring. Whether the atmospheric intraseasonal oscillations are also important for forcing the oceanic intraseasonal oscillations in the southwestern Indian Ocean needs further investigation.

* The National Center for Atmospheric Research is sponsored by the National Science Foundation

Corresponding author address: Lei Zhou, Computer and Space Sciences Bldg. 2330, University of Maryland, College Park, College Park, MD 20742. Email: lzhou@atmos.umd.edu

Abstract

The spatial and temporal features of intraseasonal oscillations in the southwestern Indian Ocean are studied by analyzing model simulations for the Indo-Pacific region. The intraseasonal oscillations have periods of 40–80 days with a wavelength of ∼650 km. They originate from the southeastern Indian Ocean and propagate westward as Rossby waves with a phase speed of ∼25 cm s−1 in boreal winter and spring. The baroclinic instability is the main driver for these intraseasonal oscillations. The first baroclinic mode dominates during most of the year, but during boreal winter and spring the second mode contributes significantly and often equally. Consequently, the intraseasonal oscillations are relatively strong in boreal winter and spring. Whether the atmospheric intraseasonal oscillations are also important for forcing the oceanic intraseasonal oscillations in the southwestern Indian Ocean needs further investigation.

* The National Center for Atmospheric Research is sponsored by the National Science Foundation

Corresponding author address: Lei Zhou, Computer and Space Sciences Bldg. 2330, University of Maryland, College Park, College Park, MD 20742. Email: lzhou@atmos.umd.edu

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