Simulation of Interannual SST Variability in the Tropical Indian Ocean

Behera, Swadhin K.; Salvekar, P. S.; Yamagata, Toshio

doi:10.1175/1520-0442(2000)013<3487:soisvi>2.0.co;2

Cited by 95 publications

(72 citation statements)

References 16 publications

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“…It is not surprising then, that the subtropical dipole index (SDI) of Suzuki et al (2004) is not significantly correlated with SWWA rainfall (Pearson correlation coefficient of 0.238, and an associated P value of 0.183). Similar correlation levels are obtained between SWWA rainfall and the SDI of Behera and Yamagata (2001). We further investigated time series of the seasonal mean SDI indices versus seasonal mean SWWA rainfall and again found no significant correlation.…”

Section: E Relation To the Iod And Siodsupporting

confidence: 74%

“…For example, the Indonesian throughflow is thought to directly influence Indian Ocean variability (Lee et al 2002;Xie et al 2002), thereby likely affecting IOD characteristics (Saji and Yamagata 2003b) as well as the heat content at pole P1. The sensitivity of the Indonesian throughflow to ENSO (Meyers 1996;Behera et al 2000;England and Huang 2005) means that it is likely that the climate of the tropical Pacific Ocean will impact SWWA rainfall via the Indian Ocean connection established in our study. There is anecdotal evidence for this, with several of the dry years coinciding with ENSO years in both the observations and the coupled climate model.…”

Section: Discussionmentioning

confidence: 99%

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Interannual Rainfall Extremes over Southwest Western Australia Linked to Indian Ocean Climate Variability

2006

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Interannual rainfall extremes over southwest Western Australia (SWWA) are examined using observations, reanalysis data, and a long-term natural integration of the global coupled climate system. The authors reveal a characteristic dipole pattern of Indian Ocean sea surface temperature (SST) anomalies during extreme rainfall years, remarkably consistent between the reanalysis fields and the coupled climate model but different from most previous definitions of SST dipoles in the region. In particular, the dipole exhibits peak amplitudes in the eastern Indian Ocean adjacent to the west coast of Australia. During dry years, anomalously cool waters appear in the tropical/subtropical eastern Indian Ocean, adjacent to a region of unusually warm water in the subtropics off SWWA. This dipole of anomalous SST seesaws in sign between dry and wet years and appears to occur in phase with a large-scale reorganization of winds over the tropical/subtropical Indian Ocean. The wind field alters SST via anomalous Ekman transport in the tropical Indian Ocean and via anomalous air-sea heat fluxes in the subtropics. The winds also change the large-scale advection of moisture onto the SWWA coast. At the basin scale, the anomalous wind field can be interpreted as an acceleration (deceleration) of the Indian Ocean climatological mean anticyclone during dry (wet) years. In addition, dry (wet) years see a strengthening (weakening) and coinciding southward (northward) shift of the subpolar westerlies, which results in a similar southward (northward) shift of the rainbearing fronts associated with the subpolar front. A link is also noted between extreme rainfall years and the Indian Ocean Dipole (IOD). Namely, in some years the IOD acts to reinforce the eastern tropical pole of SST described above, and to strengthen wind anomalies along the northern flank of the Indian Ocean anticyclone. In this manner, both tropical and extratropical processes in the Indian Ocean generate SST and wind anomalies off SWWA, which lead to moisture transport and rainfall extremes in the region. An analysis of the seasonal evolution of the climate extremes reveals a progressive amplification of anomalies in SST and atmospheric circulation toward a wintertime maximum, coinciding with the season of highest SWWA rainfall. The anomalies in SST can appear as early as the summertime months, however, which may have important implications for predictability of SWWA rainfall extremes.

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Section: E Relation To the Iod And Siodsupporting

confidence: 74%

Section: Discussionmentioning

confidence: 99%

Interannual Rainfall Extremes over Southwest Western Australia Linked to Indian Ocean Climate Variability

2006

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“…It has been suggested that modulations of the subtropical atmospheric anticyclone are responsible, although the link between atmospheric variability (i.e., anticyclone modulation) and SST variability has not been precisely determined. Investigations that have discussed the mechanism of these SST anomalies in detail have linked this latent heat flux variability to wind speed variability (e.g., Suzuki et al 2004;Behera and Yamagata 2001). Here we reexamine the anomaly formation mechanism.…”

Section: Introductionsupporting

confidence: 68%

“…This has led to a recent interest in determining the cause of these subtropical SST anomalies (cf. Behera and Yamagata 2001;Fauchereau et al 2003;Suzuki et al 2004;Hermes and Reason 2005). Latent heat variability, other components of surface heat flux, and ocean processes have all been implicated in forming these SST anomalies previously (Walker 1990;Yu and Rienecker 1999;Behera and Yamagata 2001;Suzuki et al 2004;Hermes and Reason 2005), although the strongest case has been made for latent heat flux variability being the main cause of these subtropical SST anomalies.…”

Section: Introductionmentioning

confidence: 99%

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Mechanisms of Summertime Subtropical Southern Indian Ocean Sea Surface Temperature Variability: On the Importance of Humidity Anomalies and the Meridional Advection of Water Vapor*

Chiodi

Harrison

2007

Journal of Climate

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It is well known that some austral summertime subtropical Indian Ocean sea surface temperature (SST) variability correlates with rainfall over certain regions of Africa that depend on rainfall for their economic well-being. Recent studies have determined that this SST variability is at least partially driven by latent heat flux variability, but the mechanism has not been fully described. Here, the mechanism that drives this SST variability is reexamined using analyses of operational air-sea fluxes, ocean mixed layer modeling, and simple atmospheric boundary layer physics. The SST variability of interest is confirmed to be mainly driven by latent heat flux variability, which is shown, for the first time, to be mainly caused by near-surface humidity variability. This humidity variability is then shown to be fundamentally driven by the anomalous meridional advection of water vapor. The meridional wind anomalies of interest are subsequently found to occur when the subtropical atmospheric anticyclone is preferentially located toward one of the sides (east/ west) of the basin.

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Hydrological Response and Complex Impact Pathways of the 2015/2016 El Niño in Eastern and Southern Africa

Siderius

Gannon

Ndiyoi³

et al. 2018

Earth's Future

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The 2015/2016 El Niño has been classified as one of the three most severe on record. El Niño teleconnections are commonly associated with droughts in southern Africa and high precipitation in eastern Africa. Despite their relatively frequent occurrence, evidence for their hydrological effects and impacts beyond agriculture is limited. We examine the hydrological response and impact pathways of the 2015/2016 El Niño in eastern and southern Africa, focusing on Botswana, Kenya, and Zambia. We use in situ and remotely sensed time series of precipitation, river flow, and lake levels complemented by qualitative insights from interviews with key organizations in each country about awareness, impacts, and responses. Our results show that drought conditions prevailed in large parts of southern Africa, reducing runoff and contributing to unusually low lake levels in Botswana and Zambia. Key informants characterized this El Niño through record high temperatures and water supply disruption in Botswana and through hydroelectric load shedding in Zambia. Warnings of flood risk in Kenya were pronounced, but the El Niño teleconnection did not materialize as expected in 2015/2016. Extreme precipitation was limited and caused localized impacts. The hydrological impacts in southern Africa were severe and complex, strongly exacerbated by dry antecedent conditions, recent changes in exposure and sensitivity and management decisions. Improved understanding of hydrological responses and the complexity of differing impact pathways can support design of more adaptive, region‐specific management strategies.

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Simulation of Interannual SST Variability in the Tropical Indian Ocean

Cited by 95 publications

References 16 publications

Interannual Rainfall Extremes over Southwest Western Australia Linked to Indian Ocean Climate Variability

Interannual Rainfall Extremes over Southwest Western Australia Linked to Indian Ocean Climate Variability

Mechanisms of Summertime Subtropical Southern Indian Ocean Sea Surface Temperature Variability: On the Importance of Humidity Anomalies and the Meridional Advection of Water Vapor*

Hydrological Response and Complex Impact Pathways of the 2015/2016 El Niño in Eastern and Southern Africa

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