Atlantic forced component of the Indian monsoon interannual variability

Kucharski, Fred; Bracco, Annalisa; Yoo, Jin; Molteni, Franco

doi:10.1029/2007gl033037

Cited by 187 publications

(170 citation statements)

References 36 publications

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“…The current study discusses the role of Indian Ocean warming in weakening of the monsoon, but does not rule out the possibility that similar impacts may also arise due to SST changes in the tropical Pacific and the Atlantic 9,54,[57][58][59][60][61] . Recent studies show that the Pacific warming trend during the past century is not prominent as compared with the Indian Ocean warming while the tropical and extratropical Atlantic show strong warming trends 28 .…”

Section: Discussionmentioning

confidence: 90%

Drying of Indian subcontinent by rapid Indian Ocean warming and a weakening land-sea thermal gradient

et al. 2015

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There are large uncertainties looming over the status and fate of the South Asian summer monsoon, with several studies debating whether the monsoon is weakening or strengthening in a changing climate. Our analysis using multiple observed datasets demonstrates a significant weakening trend in summer rainfall during 1901-2012 over the central-east and northern regions of India, along the Ganges-Brahmaputra-Meghna basins and the Himalayan foothills, where agriculture is still largely rain-fed. Earlier studies have suggested an increase in moisture availability and land-sea thermal gradient in the tropics due to anthropogenic warming, favouring an increase in tropical rainfall. Here we show that the land-sea thermal gradient over South Asia has been decreasing, due to rapid warming in the Indian Ocean and a relatively subdued warming over the subcontinent. Using long-term observations and coupled model experiments, we provide compelling evidence that the enhanced Indian Ocean warming potentially weakens the land-sea thermal contrast, dampens the summer monsoon Hadley circulation, and thereby reduces the rainfall over parts of South Asia.

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Section: Discussionmentioning

confidence: 90%

Drying of Indian subcontinent by rapid Indian Ocean warming and a weakening land-sea thermal gradient

et al. 2015

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“…It is also well known that the link between AIRI and ENSO has declined significantly in recent decades (Kumar et al, 1999;Torrence and Webster, 1999). Kucharski et al (2007Kucharski et al ( , 2008 have shown that the change in the Indian monsoon-ENSO connection is due to the influence of SST anomalies in the tropical Atlantic Ocean, a factor that seems likely to play a role in the dynamics of EOF-2 as well.…”

Section: The Linear Modelmentioning

confidence: 99%

Two major modes of variability of the East Asian summer monsoon

Sun

Greatbatch

Park

et al. 2010

Q.J.R. Meteorol. Soc.

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We study the two primary modes of variability associated with the East Asian summer monsoon, as identified using a multivariate Empirical Orthogonal Function (EOF) analysis. The second mode is shown to be related to changes in intensity of the South Asian High at 100 hPa while, consistent with previous work, the first mode is associated with an index for the shear vorticity of the 850 hPa zonal wind over the monsoon region. We show that a linear, dry dynamical model, when driven by the diabatic heating anomalies associated with each mode, can reproduce many of the anomalous circulation features, especially for the first EOF and in the lower troposphere. The model results indicate the importance of diabatic heating anomalies over the tropical Indian Ocean in the dynamics of both modes, especially EOF-1, and illustrate the role of local diabatic feedback for intensifying the circulation anomalies; in particular, the subtropical anticyclonic anomalies that are found in the positive phase of both modes, and the circulation anomaly associated with the Meiyu/Changma/Baiu rain band. A running cross-correlation analysis shows that the second EOF is consistently linked to both the decaying and the onset phase of El Niño/Southern Oscillation (ENSO) events throughout the study period . We attribute the connection in the onset phase to zonal wind anomalies along the Equator in the west Pacific associated with this mode. On the other hand, a link between the first EOF and ENSO is found only in the post-1979 period. We note also the role of sea-surface temperature anomalies in the tropical Indian Ocean in the dynamics of EOF-1, and a link to the variability of the Indian summer monsoon in the case of EOF-2.

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“…From another point of view, evidence of the connections between the equatorial Atlantic and the eastern tropical Pacific through the SST variability associated with the Atlantic equatorial mode (AEM) and the ENSO has been found in recent studies (Wang, 2006;Kucharski et al, 2007Kucharski et al, , 2008. The AEM, similarly to the ENSO in the Pacific, features an anomalous SST pattern roughly symmetric to the equator in the eastern side of the Atlantic Basin, and varies in a 2-5-year timescale (Zebiak, 1993;Wagner and da Silva, 1994).…”

Section: Introductionmentioning

confidence: 99%

“…While the significant positive SST anomalies weaken, the Atlantic La Niña pattern becomes better established from November/December to December/January. Several authors have shown that an Atlantic La Niña induces the establishment of a Pacific El Niño through an east-west anomalous circulation (Wang, 2006;Kucharski et al, 2007Kucharski et al, , 2008Kayano et al, 2010) during the subsequent months. This is the case here, as a negative inter-PacificAtlantic anomalous SST gradient is established from January/February to March/April (Figure 2a)).…”

Section: Rainy Seasonmentioning

confidence: 99%

Seasonal anomalous rainfall in the central and eastern Amazon and associated anomalous oceanic and atmospheric patterns

Andreoli

Souza

Kayano

et al. 2011

Intl Journal of Climatology

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ABSTRACT:Previous papers have shown that the rainfall anomalies over the Amazon region result from the independent or combined effects of the eastern tropical Pacific and Atlantic Basins. Here, the monthly rainfall data of Itaituba, Manaus, Parintins, and Santarém for the 1931-1996 period has been used to classify its dry and rainy seasons into dry, very dry, wet, and very wet categories. The sea surface temperature (SST) and sea level pressure (SLP) patterns associated with these climate conditions in the central and eastern Amazon are discussed in terms of the relative influence of the tropical Atlantic and Pacific sectors, as well as their seasonal differences. These seasonal differences are, in part, determined by the seasonal phase locking of the El Niño-Southern Oscillation (ENSO) and Atlantic equatorial modes. The rainy season cases are mostly driven by the ENSO and the inter-hemispheric SST gradient mode in the tropical Atlantic, and the dry season cases, by the Atlantic equatorial mode (AEM). A new result here is the role of the inter-Pacific-Atlantic anomalous SST gradient mode on the rainfall anomalies. This mode acts concordantly with the Atlantic modes on the rainfall over the central and eastern Amazon, and is responsible for precipitation extreme cases during the dry season and for the very wet rainy season case. In other words, the intense inter-Pacific-Atlantic mode for these cases is the differential factor in relation to the moderate cases. The results here, especially in relation to the role of the inter-Pacific-Atlantic gradient in the central and eastern Amazon precipitation, have not been discussed before and should be taken into consideration in the diagnostic activities.

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Atlantic forced component of the Indian monsoon interannual variability

Cited by 187 publications

References 36 publications

Drying of Indian subcontinent by rapid Indian Ocean warming and a weakening land-sea thermal gradient

Drying of Indian subcontinent by rapid Indian Ocean warming and a weakening land-sea thermal gradient

Two major modes of variability of the East Asian summer monsoon

Seasonal anomalous rainfall in the central and eastern Amazon and associated anomalous oceanic and atmospheric patterns

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