Madden‐Julian Oscillation and sea level: Local and remote forcing

Oliver, Eric C. J.; Thompson, Keith R.

doi:10.1029/2009jc005337

Cited by 56 publications

(66 citation statements)

References 43 publications

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“…This realistic behaviour is evident even from model simulations forced by an idealised Gaussian westerly wind burst on the equator in the Indian Ocean. The subsequent wave propagation shows many of the features identified in previous studies of the dynamics of this ocean basin in response to wind forcing by the MJO (Oliver and Thompson 2010;Webber et al 2010). Crucially, the arrival of downwelling oceanic equatorial Rossby waves in the western Indian Ocean around 90 days after the initial wind burst agrees with the findings of Webber et al (2010) and with hypotheses of coupling between the atmosphere and the ocean dynamics on such time scales (Han et al 2001;Han 2005;Fu 2007).…”

Section: Discussion a Ocean Dynamicsmentioning

confidence: 66%

Dynamical Ocean Forcing of the Madden–Julian Oscillation at Lead Times of up to Five Months

et al. 2012

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The authors show that a simple three-dimensional ocean model linearized about a resting basic state can accurately simulate the dynamical ocean response to wind forcing by the Madden–Julian oscillation (MJO). This includes the propagation of equatorial waves in the Indian Ocean, from the generation of oceanic equatorial Kelvin waves to the arrival of downwelling oceanic equatorial Rossby waves in the western Indian Ocean, where they have been shown to trigger MJO convective activity. Simulations with idealized wind forcing suggest that the latitudinal width of this forcing plays a crucial role in determining the potential for such feedbacks. Forcing the model with composite MJO winds accurately captures the global ocean response, demonstrating that the observed ocean dynamical response to the MJO can be interpreted as a linear response to surface wind forcing. The model is then applied to study “primary” Madden–Julian events, which are not immediately preceded by any MJO activity or by any apparent atmospheric triggers, but have been shown to coincide with the arrival of downwelling oceanic equatorial Rossby waves. Case study simulations show how this oceanic equatorial Rossby wave activity is partly forced by reflection of an oceanic equatorial Kelvin wave triggered by a westerly wind burst 140 days previously, and partly directly forced by easterly wind stress anomalies around 40 days prior to the event. This suggests predictability for primary Madden–Julian events on times scales of up to five months, following the reemergence of oceanic anomalies forced by winds almost half a year earlier.

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Section: Discussion a Ocean Dynamicsmentioning

confidence: 66%

Dynamical Ocean Forcing of the Madden–Julian Oscillation at Lead Times of up to Five Months

et al. 2012

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“…These SSH anomalies could propagate westward by radiating Rossby waves from the eastern boundary, e.g., [37][38][39][40][41]. Figure 9 shows the longitude-time diagram of SSH at 4°N and 4°S.…”

Section: Remote Response To the Mjo Eventsmentioning

confidence: 99%

Large-Scale Oceanic Variability Associated with the Madden-Julian Oscillation during the CINDY/DYNAMO Field Campaign from Satellite Observations

et al. 2013

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During the CINDY/DYNAMO field campaign (fall/winter 2011), intensive measurements of the upper ocean, including an array of several surface moorings and ship observations for the area around 75°E-80°E, Equator-10°S, were conducted. In this study, large-scale upper ocean variations surrounding the intensive array during the field campaign are described based on the analysis of satellite-derived data. Surface currents, sea surface height (SSH), sea surface salinity (SSS), surface winds and sea surface temperature (SST) during the CINDY/DYNAMO field campaign derived from satellite observations are analyzed. During the intensive observation period, three active episodes of large-scale convection associated with the Madden-Julian Oscillation (MJO) propagated eastward across the tropical Indian Ocean. Surface westerly winds near the equator were particularly strong during the events in late November and late December, exceeding 10 m/s. These westerlies generated strong eastward jets (>1 m/s) on the equator. Significant remote ocean responses to the equatorial westerlies were observed in both Northern and Southern Hemispheres in the central and eastern Indian Oceans. The anomalous SSH associated with strong eastward jets propagated eastward as an equatorial Kelvin wave and generated OPEN ACCESSRemote Sens. 2013, 5 2073 intense downwelling near the eastern boundary. The anomalous positive SSH then partly propagated westward around 4°S as a reflected equatorial Rossby wave, and it significantly influenced the upper ocean structure in the Seychelles-Chagos thermocline ridge about two months after the last MJO event during the field campaign. For the first time, it is demonstrated that subseasonal SSS variations in the central Indian Ocean can be monitored by Aquarius measurements based on the comparison with in situ observations at three locations. Subseasonal SSS variability in the central Indian Ocean observed by RAMA buoys is explained by large-scale water exchanges between the Arabian Sea and Bay of Bengal through the zonal current variation near the equator.

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“…In the Indian Ocean, the dynamical ocean response to the MJO consists of equatorial Kelvin waves which reflect into equatorial Rossby waves on reaching the coast of Sumatra (Oliver and Thompson, 2010;Webber et al, 2010). These reflected Rossby waves propagate westwards to arrive in the western Indian Ocean approximately 90 days later, where they lead to positive SST anomalies and thus trigger convection within the region where MJO events are initiated (Webber et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Ocean Rossby waves as a triggering mechanism for primary Madden–Julian events

Webber

Matthews

Heywood

et al. 2011

Quart J Royal Meteoro Soc

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The Madden-Julian Oscillation (MJO) is sporadic, with episodes of cyclical activity interspersed with inactive periods. However, it remains unclear what may trigger a Madden-Julian (MJ) event which is not immediately preceded by any MJO activity: a 'primary' MJ event. A combination of case-studies and composite analysis is used to examine the extent to which the triggering of primary MJ events might occur in response to ocean dynamics. The case-studies show that such events can be triggered by the arrival of a downwelling oceanic equatorial Rossby wave, which is shown to be associated with a deepening of the mixed layer and positive sea-surface temperature (SST) anomalies of the order of 0.5-1• C. These SST anomalies are not attributable to forcing by surface fluxes which are weak for the case-studies analysed. Furthermore, composite analysis suggests that such forcing is consistently important for triggering primary events. The relationship is much weaker for successive events, due to the many other triggering mechanisms which operate during periods of cyclical MJO activity. This oceanic feedback mechanism is a viable explanation for the sporadic and broadband nature of the MJO. Additionally, it provides hope for forecasting MJ events during periods of inactivity, when MJO forecasts generally exhibit low skill.

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Madden‐Julian Oscillation and sea level: Local and remote forcing

Cited by 56 publications

References 43 publications

Dynamical Ocean Forcing of the Madden–Julian Oscillation at Lead Times of up to Five Months

Dynamical Ocean Forcing of the Madden–Julian Oscillation at Lead Times of up to Five Months

Large-Scale Oceanic Variability Associated with the Madden-Julian Oscillation during the CINDY/DYNAMO Field Campaign from Satellite Observations

Ocean Rossby waves as a triggering mechanism for primary Madden–Julian events

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