Interannual modulation and its dynamics of the mesoscale eddy variability in the southeastern tropical Indian Ocean

Ogata, Tomomichi; Masumoto, Yukio

doi:10.1029/2010jc006490

Cited by 21 publications

(13 citation statements)

References 32 publications

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“…Additionally, both were long‐lived, at ~240 days for the January 2004 feature (Figure (c)) and > 240 days for the April 2009 feature (Figure (d)). The wavelengths and intraseasonal periods are consistent with observed and model simulated instabilities associated with the South Equatorial Current in these latitudinal regions noted by previous studies (e.g., Feng & Wijffels, ; Ogata & Masumoto, , ; Trenary & Han, ; Yu & Potemra, ). Other studies (see, e.g., Chelton et al, ) have noted that oceanic eddies associated with instabilities propagate with similar phase speeds to Rossby waves.…”

Section: Resultssupporting

confidence: 90%

The Role of Oceanic Processes in the Initiation of Boreal Winter Intraseasonal Oscillations Over the Indian Ocean

et al. 2020

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Observational analyses and ocean general circulation model experiments were performed to understand the influence of oceanic processes on warm sea surface temperature anomalies (SSTAs) prior to convection initiation of boreal winter intraseasonal oscillations (ISOs), including the Madden‐Julian Oscillation (MJO), in the tropical Indian Ocean. We found 39 strong ISOs that passed over the Indian Ocean Warm Pool (WP) region during the November–April season of the 2001–2012 period. Seventeen of them (44%) initiated over the Seychelles‐Chagos Thermocline Ridge (SCTR) before propagating eastward to the WP and Maritime Continent. Including only global‐scale MJOs, 71% (24%) of the remaining MJO events initiated from the SCTR (WP). Four (seven) SCTR (WP) ISO events were preceded by SSTAs that were strongly influenced by wind stress‐driven oceanic processes; all four (2/7) SCTR (WP) events were MJOs. Composite analyses of the four oceanic process influenced SCTR MJO events showed that wind stress‐driven oceanic processes contributed about 30% (between 0.1 and 0.2 °C) of the preconvection warming in the SCTR, which coincides with the Intertropical Convergence Zone with mean SST > 28 °C. Reduced upwelling and entrainment played a more important role than horizontal advection in elevating the +SSTAs. Case studies revealed that the two ocean process‐influenced primary MJO SCTR events were also associated with oceanic equatorial Rossby waves. Furthermore, results of a linear atmospheric mixed layer model indicated that boundary layer processes related to SSTAs contributed approximately half of the total convergence during MJO initiation, relative to the effect of the free troposphere, for the Rossby wave‐influenced events.

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Section: Resultssupporting

confidence: 90%

The Role of Oceanic Processes in the Initiation of Boreal Winter Intraseasonal Oscillations Over the Indian Ocean

et al. 2020

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“…Mesoscale eddies play a critical role in the ocean circulation through mass and heat transport (Chelton, 2013;Dong et al, 2014;Zhang et al, 2014). Barotropic and baroclinic instabilities are the main source of eddy generation (Ogata & Masumoto, 2011). The barotropic instability converts kinetic energy of mean flows to eddy energy, and the baroclinic instability converts potential energy of mean flows to eddy energy.…”

Section: Introductionmentioning

confidence: 99%

Interannual Variability of Eddy Kinetic Energy in the Subtropical Southeast Indian Ocean Associated With the El Niño‐Southern Oscillation

Zheng

Feng

et al. 2018

JGR Oceans

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Interannual variability of eddy kinetic energy (EKE) in the subtropical southeast Indian Ocean (SEIO) is investigated using satellite observations in three regions in the 20°S–35°S latitude band: R1 (108°E–115°E), R2 (100°E–108°E), and R3 (60°E–100°E). The El Niño‐Southern Oscillation (ENSO) plays an important role in modulating the interannual variability of EKE in the SEIO. EKE in the three regions shows negative correlations with the Nino3.4, lagging Nino3.4 by 2, 14, and 22 months, respectively. In R1, the ENSO modulates the interannual variability of EKE through influencing baroclinic instability of meridional velocity shear between the upper poleward Leeuwin Current (LC) and the underlying equatorward Leeuwin Undercurrent (LUC). During La Niña (El Niño) year, both the poleward LC and equatorward LUC strengthened (weakened) due to the high (low) sea level anomaly (SLA) propagating from the Pacific Ocean as Rossby wave under geostrophic equilibrium, and baroclinic instability of vertical shear enhanced (slackened), further induced the strong (weak) EKE in the eastern boundary. In R2, the ENSO modulates the interannual variability of EKE through influencing baroclinic instability of zonal velocity shear between the central and southern branches of the upper eastward South Indian Countercurrent (SICC) and the lower extending westward South Equatorial Current (SEC). In R3, both the ENSO and the Southern Annual Mode modulate the interannual variability of EKE through influencing baroclinic instability of zonal velocity shear between the SICC and SEC. The interannual variability of EKE in the interior SEIO could be influenced by westward propagation of EKE originated from eastern boundary.

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“…In addition to the oceanic variability forced by atmospheric forcing fields at the surface and from the ITF, oceanic variability can also arise from internal variability due to nonlinearity of the oceanic system. Previous studies reported the effects of oceanic internal variability in generating “intraseasonal timescale” variability near the Somali coast, in the southwest tropical basin, and the South Equatorial Current region of the Indian Ocean [e.g., Kindle and Thompson , ; Woodberry et al ., ; Tsai et al ., ; Jochum and Murtugudde , ; Feng and Wijffels , ; Yu and Potemra , ; Han et al ., ; Palastanga et al ., ; Ogata and Masumoto , , ; Trenary and Han , ]. Levels of high eddy kinetic energy found in the 20°S–30°S band of the South Indian Ocean undergo large seasonal and interannual variations, resulting from varying vertical shear of the South Indian Counter Current‐South Equatorial Current system [e.g., de Ruijter et al ., ; Palastanga et al ., ; Jia et al ., , ].…”

Section: Introductionmentioning

confidence: 99%

Local and remote forcing of decadal sea level and thermocline depth variability in the South Indian Ocean

Trenary

Han

2013

JGR Oceans

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Analysis is performed on a set of diagnostic numerical experiments designed to isolate local Indian Ocean forcing versus remote forcing from the Pacific via the Indonesian throughflow on decadal variability of subsurface temperature, sea level, and thermocline depth of the South Indian Ocean. It is found that the vertical structure of decadal temperature variability varies from decade‐to‐decade, with maximum variation peaking in the vicinity of the thermocline. The decadal‐scale temperature variations in the tropical southwestern Indian Ocean between 5°S and 17°S are primarily associated with the vertical displacements of the thermocline. Prior to the early 1990s, decadal variations in sea level and thermocline depth can be described in terms of a baroclinic Sverdrup balance, forced by Ekman pumping velocity associated with windstress curl acting on the Indian Ocean. Beginning in the early 1990s, decadal variability of the equatorial Pacific trades forces thermocline variations that modify the sea level and thermocline depth across the tropical South Indian Ocean basin. Farther south, between 20°S and 30°S, oceanic internal variability makes significant contributions to decadal variability of the thermocline. The anomalies along the western coast of Australia are primarily driven by regional forcing acting on the Indian Ocean prior to the 1990s, and signals originating from the equatorial Pacific make a greater contribution thereafter.

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Interannual modulation and its dynamics of the mesoscale eddy variability in the southeastern tropical Indian Ocean

Cited by 21 publications

References 32 publications

The Role of Oceanic Processes in the Initiation of Boreal Winter Intraseasonal Oscillations Over the Indian Ocean

The Role of Oceanic Processes in the Initiation of Boreal Winter Intraseasonal Oscillations Over the Indian Ocean

Interannual Variability of Eddy Kinetic Energy in the Subtropical Southeast Indian Ocean Associated With the El Niño‐Southern Oscillation

Local and remote forcing of decadal sea level and thermocline depth variability in the South Indian Ocean

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