On the relationship between Indian summer monsoon withdrawal and Indo-Pacific SST anomalies before and after 1976/1977 climate shift

C. T. Sabeerali, Suryachandra A. Rao, Ajaya Ravindran, Raghu Murtugudde

    Research output: Contribution to journalArticle

    Abstract

    A clear shift in the withdrawal dates of the Indian Summer Monsoon is observed in the long term time series of rainfall data. Prior (posterior) to the 1976/1977 climate shift most of the withdrawal dates are associated with a late (an early) withdrawal. As a result, the length of the rainy season (LRS) over the Indian land mass has also undergone similar changes (i. e., longer (shorter) LRS prior (posterior) to the climate shift). In this study, probable reasons for this significant shift in withdrawal dates and the LRS are investigated using reanalysis/observed datasets and also with the help of an atmospheric general circulation model. Reanalysis/observational datasets indicate that prior to the climate shift the sea surface temperature (SST) anomalies in the eastern equatorial Pacific Ocean and the Arabian Sea exerted a strong influence on both the withdrawal and the LRS. After the climate shift, the influence of the eastern equatorial Pacific Ocean SST has decreased and surprisingly, the influence of the Arabian Sea SST is almost non-existent. On the other hand, the influence of the southeastern equatorial Indian Ocean has increased significantly. It is observed that the upper tropospheric temperature gradient over the dominant monsoon region has decreased and the relative influence of the Indian Ocean SST variability on the withdrawal of the Indian Summer Monsoon has increased in the post climate shift period. Sensitivity experiments with the contrasting SST patterns on withdrawal dates and the LRS in the pre- and post- climate shift scenarios, confirm the observational evidences presented above.

    Original languageEnglish (US)
    Pages (from-to)841-859
    Number of pages19
    JournalClimate Dynamics
    Volume39
    Issue number3
    DOIs
    StatePublished - Jul 1 2012

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    temperature anomaly
    monsoon
    sea surface temperature
    climate
    summer
    sea surface
    atmospheric general circulation model
    temperature gradient
    time series
    rainfall
    ocean
    experiment
    sea
    Indian Ocean

    Keywords

    • Climate shift
    • El Niño
    • Indian monsoon
    • Indian Ocean Dipole

    ASJC Scopus subject areas

    • Atmospheric Science

    Cite this

    On the relationship between Indian summer monsoon withdrawal and Indo-Pacific SST anomalies before and after 1976/1977 climate shift. / Sabeerali, C. T.; Rao, Suryachandra A.; Ravindran, Ajaya; Murtugudde, Raghu.

    In: Climate Dynamics, Vol. 39, No. 3, 01.07.2012, p. 841-859.

    Research output: Contribution to journalArticle

    Sabeerali, C. T. ; Rao, Suryachandra A. ; Ravindran, Ajaya ; Murtugudde, Raghu. / On the relationship between Indian summer monsoon withdrawal and Indo-Pacific SST anomalies before and after 1976/1977 climate shift. In: Climate Dynamics. 2012 ; Vol. 39, No. 3. pp. 841-859.
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