Detection of the Madden–Julian Oscillation in the Indian Ocean From Satellite Altimetry

Grunseich, Gary; Subrahmanyam, Bulusu

doi:10.1109/lgrs.2012.2208261

Cited by 9 publications

(9 citation statements)

References 12 publications

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“…This is consistent with the findings of other studies in the Indian Ocean, which found satellite salinity products (e.g. Aquarius, SMOS, and SMAP) to have a comparable standard error (Grunseich & Subrahmanyam, ; Guan et al, ). SODA SSS and ORAS5 SSS were found to be the closest to Argo.…”

Section: Resultssupporting

confidence: 92%

The Role of Salinity in the Southeastern Arabian Sea in Determining Monsoon Onset and Strength

2020

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In this study, we examine the role of freshwater transported from the Bay of Bengal into the southeastern Arabian Sea (SEAS) in determining both the timing of monsoon onset and the strength of the ensuing monsoon. To do this, we use a combination of satellite-derived salinity data and reanalysis products from 1980 to 2016 in order to discuss seasonal, interannual, subdecadal, and long-term decadal variability in various atmospheric and oceanic contributors such as ocean heat content, freshwater transport, ERA5 instantaneous moisture flux, mixed layer depth, and barrier layer thickness. The salt budget in the SEAS reveals the dominance of meridional freshwater advective transport that brings in variability in salinity and thus in salinity stratification, as well as in mixed layer processes. We find that these parameters exhibit the prevalence of a long-term decadal variability (with trends of increasing/decreasing phases over a 15-year duration) over which interannual (3-year trend) and intradecadal (7-year trend) variability trends are superimposed. The patterns of both the 3-and 7-year trends follow each other closely, and relatively high amplitudes are seen in the 3-year trends. The long-term decrease in moisture flux and freshwater transport into the SEAS along with a rise in ocean heat content over a 15-year duration after 1994 contributed to a lack of strong monsoons in recent years; the prevailing interannual and intradecadal variability in these parameters associated with the Indian Ocean Dipole and El Niño Southern Oscillation events favored weaker and normal monsoons after 1994. Plain Language SummaryThe timing and intensity of the southwest monsoon is difficult to forecast and has been the subject of a great deal of research. In particular, the genesis of a monsoon onset vortex over the southeastern Arabian Sea (SEAS) encompassing the Arabian Sea Mini Warm Pool has received increased attention for the role it plays on the onset of the southwest monsoon. In our study, we examine how the low salinity waters transported from the Bay of Bengal (both along the east coast of India and from the southern Bay of Bengal) into the SEAS region influence the strength and timing of the ensuing southwest monsoon. Our finding is that this low salinity water has a significant impact on barrier layer formation in the SEAS and the vertical thermal structure of the Arabian Sea Mini Warm Pool. Further examination of subdecadal, decadal, and long-period decadal trends from 1980 to 2016 shows that instantaneous moisture fluxes and zonal winds over the SEAS have decreased substantially, and barrier layer thickness has increased since 1994 in association with the increasing trend in ocean heat content and contributed to the lack of strong southwest monsoons after 1994.

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Section: Resultssupporting

confidence: 92%

The Role of Salinity in the Southeastern Arabian Sea in Determining Monsoon Onset and Strength

2020

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“…The seasonal reversal of winds in the Somali Current region trigger an equatorial Kelvin wave response that propagate eastward across the Indian Ocean and reflect back as a downwelling Rossby wave. This Rossby wave deepens the mixed layer and thermocline, warming sea surface temperatures (SSTs), and triggering atmospheric MJO convection (Aiyyer & Molinari, ; Chen et al, ; Grunseich, Subrahmanyam, Arguez, ; Grunseich, Subrahmanyam, Murty, et al, ; Grunseich & Subrahmanyam, ; Hendon et al, ; Li et al, ; Matthews, ; Webber et al, , ). Using satellite altimetry data, Grunseich and Subrahmanyam () were able to confirm the impact Kelvin and Rossby waves have on MJO initiation, showing that satellite observations can be used to accurately monitor and predict these ISOs.…”

Section: Introductionmentioning

confidence: 99%

Monitoring Intraseasonal Oscillations in the Indian Ocean Using Satellite Observations

2020

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Intraseasonal oscillations (ISOs) in the Indian Ocean play a significant role in determining the active (wet) and break (dry) cycles of the southwest monsoon rainfall. In this study, we use satellite‐derived precipitation, sea level anomalies (SLAs), sea surface salinity (SSS), sea surface temperature, and surface winds to monitor the 30‐90‐day, 10‐20‐day, and 3‐7‐day ISOs, and how they influence local dynamics. The main focus of this work, however, is showing the importance of using SLA and SSS to monitor ISOs. Mixed Rossby gravity waves were found to induce convection associated with the southern cell of the 10‐20‐day mode, with surface winds from the northern cell modulating coastal Kelvin waves in the Bay of Bengal. The 10‐20‐day SSS response is instead more closely related to wind‐induced upwelling in the central Bay of Bengal and river runoff in the northern Bay. The 3‐7‐day mode was found to have a weak oceanic signal, as the monsoon trough is mainly positioned over land, though SSS captured the structure of the signal most clearly. This study highlights the need for high spatial resolution SLA in order to adequately capture 3‐7‐day oscillations in the monsoon trough.

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“…The MJO has been studied using various observations of the large‐scale characteristics of the atmosphere and ocean, mostly from satellites due to their comprehensive spatiotemporal coverage. These include outgoing longwave radiation (OLR), precipitation and wind for the atmosphere, and SST and sea surface height for the ocean [ Hendon and Salby , ; Arguez et al , ; Benedict and Randall , ; Waliser et al , ; Grunseich and Bulusu , ]. Observational studies inferring interactions between the MJO and the near‐surface ocean date back over two decades [ Krishnamurti et al , ; Kawamura , ; see reviews by Hendon , ; Duvel , ].…”

Section: Introductionmentioning

confidence: 99%

“…Such ocean feedback considerably improved MJO simulations and MJO predictability/predictive skills for some coupled ocean-atmosphere models [Flatau et al, 1997;Waliser et al, 1999;Inness et al, 2003;Fu et al, 2007Fu et al, , 2013, suggesting potential importance of the ocean in understanding and predicting the MJO.The MJO has been studied using various observations of the large-scale characteristics of the atmosphere and ocean, mostly from satellites due to their comprehensive spatiotemporal coverage. These include outgoing longwave radiation (OLR), precipitation and wind for the atmosphere, and SST and sea surface height for the ocean [Hendon and Salby, 1994;Arguez et al, 2005;Benedict and Randall, 2007;Waliser et al, 2009;Grunseich and Bulusu, 2013]. Observational studies inferring interactions between the MJO and the near-surface ocean date back over two decades [Krishnamurti et al…”

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confidence: 99%

Aquarius surface salinity and the Madden‐Julian Oscillation: The role of salinity in surface layer density and potential energy

Guan

Lee

Halkides

et al. 2014

Geophysical Research Letters

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Sea surface salinity (SSS) data from the Aquarius satellite are analyzed along with auxiliary data to investigate the SSS signature of the Madden-Julian Oscillation (MJO) in the equatorial Indian and Pacific Oceans, the effect of evaporation-minus-precipitation (E-P), the implication for the role of ocean dynamics, and the SSS influence on surface density and potential energy. MJO-related SSS changes are consistent with E-P forcing in the western Indian Ocean throughout the MJO cycle and in the central Indian Ocean during the wet phase of the MJO cycle. However, SSS changes cannot be explained by E-P in the central Indian Ocean during the dry phase and in the eastern Indian and western Pacific Oceans throughout the MJO cycle, implying the importance of ocean dynamics. SSS has an overall larger contribution to MJO-related surface density and potential energy anomalies than SST. It partially offsets the SST effect in the western-to-central Indian Ocean and reinforces the SST effect in the eastern Indian and western Pacific Oceans. Ocean modeling and assimilation need to properly account for salinity effects in order to correctly represent mixed layer variability associated with the MJO. Our results also clarify some discrepancy in previous studies about the E-P effect on MJO-related SSS variations.

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Detection of the Madden–Julian Oscillation in the Indian Ocean From Satellite Altimetry

Cited by 9 publications

References 12 publications

The Role of Salinity in the Southeastern Arabian Sea in Determining Monsoon Onset and Strength

The Role of Salinity in the Southeastern Arabian Sea in Determining Monsoon Onset and Strength

Monitoring Intraseasonal Oscillations in the Indian Ocean Using Satellite Observations

Aquarius surface salinity and the Madden‐Julian Oscillation: The role of salinity in surface layer density and potential energy

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