Ocean temperature and salinity components of the Madden–Julian oscillation observed by Argo floats

Matthews, Adrian J.; Singhruck, Patama; Heywood, Karen J.

doi:10.1007/s00382-009-0631-7

Cited by 50 publications

(72 citation statements)

References 51 publications

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“…These anomalies are maximum around 100 m depth but extend coherently into the deep ocean with a slight westward tilt with increasing depth. This tilt implies upward phase propagation and downward energy propagation and has been observed in equatorial Kelvin waves for the Pacific Ocean forced by the MJO (Matthews et al 2007(Matthews et al , 2010. The coherent propagation across the width of the Indian Ocean reinforces the hypothesis that the wave activity can be traced back to reflection of the equatorial Kelvin wave incident on the eastern boundary prior to day −100.…”

Section: Rossby Wave Vertical Structuresupporting

confidence: 76%

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: Rossby Wave Vertical Structuresupporting

confidence: 76%

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

et al. 2012

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“…The anomalies in both vertical velocity and density extend down below 300 m (Figure 4(f)), associated with downward propagation of wave energy into the deep ocean, consistent with the results of Matthews et al (2007Matthews et al ( , 2010. The westward tilt of the anomalies with depth is consistent with upward phase propagation and downward energy propagation.…”

Section: Case-studiessupporting

confidence: 75%

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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“…This study revealed that patterns of anomalous mixed layer temperature in the Indian and western Pacific Oceans are consistent with being forced by anomalies in heat flux that arise from MJO convective and wind anomalies. In addition, Matthews et al (2010) showed that subsurface salinity variations at MJO time scales, which are dominated by anomalies in precipitation minus evaporation in the Indian Ocean and zonal advection in the western Pacific Ocean, have different spatial and temporal characteristics than those of temperature. This implies that there may be variations in the upper-ocean density structure, and thus MLD, at MJO time scales.…”

Section: Introductionmentioning

confidence: 98%

“…Those studies that did include in situ subsurface observations have primarily been limited to mooring sites (e.g., Anderson et al 1996;Zhang and McPhaden 2000;Vialard et al 2008) or the inclusion of Argo profiling floats in a small regional domain (e.g., Han et al 2007;Vinayachandran and Saji 2008;Sato et al 2011), and very few studies have used in situ observations to characterize the MJO signal over a large domain. Matthews et al (2010) used Argo data to characterize MJO-related anomalies of temperature and salinity throughout the water column. This study revealed that patterns of anomalous mixed layer temperature in the Indian and western Pacific Oceans are consistent with being forced by anomalies in heat flux that arise from MJO convective and wind anomalies.…”

Section: Introductionmentioning

confidence: 99%

In Situ Observations of Madden–Julian Oscillation Mixed Layer Dynamics in the Indian and Western Pacific Oceans

et al. 2012

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The boreal winter response of the ocean mixed layer to the Madden-Julian oscillation (MJO) in the IndoPacific region is determined using in situ observations from the Argo profiling float dataset. Composite averages over numerous events reveal that the MJO forces systematic variations in mixed layer depth and temperature throughout the domain. Strong MJO mixed layer depth anomalies (.15 m peak to peak) are observed in the central Indian Ocean and in the far western Pacific Ocean. The strongest mixed layer temperature variations (.0.68C peak to peak) are found in the central Indian Ocean and in the region between northwest Australia and Java. A heat budget analysis is used to evaluate which processes are responsible for mixed layer temperature variations at MJO time scales. Though uncertainties in the heat budget are on the same order as the temperature trend, the analysis nonetheless demonstrates that mixed layer temperature variations associated with the canonical MJO are driven largely by anomalous net surface heat flux. Net heat flux is dominated by anomalies in shortwave and latent heat fluxes, the relative importance of which varies between active and suppressed MJO conditions. Additionally, rapid deepening of the mixed layer in the central Indian Ocean during the onset of active MJO conditions induces significant basin-wide entrainment cooling. In the central equatorial Indian Ocean, MJO-induced variations in mixed layer depth can modulate net surface heat flux, and therefore mixed layer temperature variations, by up to ;40%. This highlights the importance of correctly representing intraseasonal mixed layer depth variations in climate models in order to accurately simulate mixed layer temperature, and thus air-sea interaction, associated with the MJO.

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Ocean temperature and salinity components of the Madden–Julian oscillation observed by Argo floats

Cited by 50 publications

References 51 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

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

In Situ Observations of Madden–Julian Oscillation Mixed Layer Dynamics in the Indian and Western Pacific Oceans

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