Influence of the Indian Ocean Dipole on the large-scale circulation in South America

Sena, Ana C.  T.; Magnusdottir, Gudrun

doi:10.1175/jcli-d-20-0669.1

Title: Influence of the Indian Ocean Dipole on the large-scale circulation in South America

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Abstract

The influence of each phase of the Indian Ocean Dipole (IOD) on the largescale circulation in South America is investigated using rainfall observations, fully-coupled, large-ensemble, historical simulations (LENS), and forced experiments using the coupled model’s atmospheric component. IOD events often occur when El Niño Southern Oscillation (ENSO), the largest source of interannual variability of precipitation in South America, is active. To distinguish from effects of ENSO, only cases during neutral ENSO conditions are analyzed in LENS and observations. During the positive IOD polarity, a perturbation in the localWalker circulation leads to increased convection over equatorial South America, resulting in wet anomalies in the Amazon basin. This signal is the opposite of what is expected during El Niño events. Tropical convection anomalies in the Indian Ocean also force an extratropical Rossby wave train that reaches subtropical South America. During positive IOD, the moisture flux from the Amazon to central and southeastern Brazil weakens, resulting in a drying of the area associated with the South Atlantic Convergence Zone. Meanwhile, the South Atlantic Subtropical High strengthens, contributing to a drying in southeastern Brazil. During negative IOD, the induced wave train from the Indian Ocean leads to increased moisture transport to the La Platamore »« less

Authors:

Sena, Ana C. T. ^[1]; Magnusdottir, Gudrun ^[1]

Univ. of California, Irvine, CA (United States). Dept. of Earth System Science

Publication Date:: Thu Apr 22 00:00:00 EDT 2021

Research Org.:: Univ. of California, Irvine, CA (United States)

Sponsoring Org.:: USDOE Office of Science (SC)

OSTI Identifier:: 1853226

Grant/Contract Number:: SC0019407

Resource Type:: Accepted Manuscript

Journal Name:: Journal of Climate

Additional Journal Information:: Journal Volume: 34; Journal Issue: 15; Journal ID: ISSN 0894-8755

Publisher:: American Meteorological Society

Country of Publication:: United States

Language:: English

Subject:: 54 ENVIRONMENTAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Meteorology & Atmospheric Sciences; Atmosphere; Indian Ocean; South America; Dynamics; Teleconnections; Interannual variability

Citation Formats


                    Sena, Ana C.  T., and Magnusdottir, Gudrun. Influence of the Indian Ocean Dipole on the large-scale circulation in South America.  United States: N. p., 2021. 
Web.  doi:10.1175/jcli-d-20-0669.1.

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                    Sena, Ana C.  T., & Magnusdottir, Gudrun. Influence of the Indian Ocean Dipole on the large-scale circulation in South America.  United States.  https://doi.org/10.1175/jcli-d-20-0669.1

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                    Sena, Ana C.  T., and Magnusdottir, Gudrun. Thu .  
"Influence of the Indian Ocean Dipole on the large-scale circulation in South America".  United States.  https://doi.org/10.1175/jcli-d-20-0669.1.  https://www.osti.gov/servlets/purl/1853226.

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@article{osti_1853226,

  title        = {Influence of the Indian Ocean Dipole on the large-scale circulation in South America},

  author       = {Sena, Ana C.  T. and Magnusdottir, Gudrun},

  abstractNote = {The influence of each phase of the Indian Ocean Dipole (IOD) on the largescale circulation in South America is investigated using rainfall observations, fully-coupled, large-ensemble, historical simulations (LENS), and forced experiments using the coupled model’s atmospheric component. IOD events often occur when El Niño Southern Oscillation (ENSO), the largest source of interannual variability of precipitation in South America, is active. To distinguish from effects of ENSO, only cases during neutral ENSO conditions are analyzed in LENS and observations. During the positive IOD polarity, a perturbation in the localWalker circulation leads to increased convection over equatorial South America, resulting in wet anomalies in the Amazon basin. This signal is the opposite of what is expected during El Niño events. Tropical convection anomalies in the Indian Ocean also force an extratropical Rossby wave train that reaches subtropical South America. During positive IOD, the moisture flux from the Amazon to central and southeastern Brazil weakens, resulting in a drying of the area associated with the South Atlantic Convergence Zone. Meanwhile, the South Atlantic Subtropical High strengthens, contributing to a drying in southeastern Brazil. During negative IOD, the induced wave train from the Indian Ocean leads to increased moisture transport to the La Plata basin, leading to wet anomalies in the region.},

  doi          = {10.1175/jcli-d-20-0669.1},

  journal      = {Journal of Climate},

  number       = 15,

  volume       = 34,

  place        = {United States},

  year         = {Thu Apr 22 00:00:00 EDT 2021},

  month        = {Thu Apr 22 00:00:00 EDT 2021}

}

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