Previous studies have shown that the Atlantic Multidecadal Oscillation （AMO） can play an important role in modulating the variabilityoflndian summer monsoon rainfall （ISMR） over a 50-60-yr timescale. A significant...Previous studies have shown that the Atlantic Multidecadal Oscillation （AMO） can play an important role in modulating the variabilityoflndian summer monsoon rainfall （ISMR） over a 50-60-yr timescale. A significant positive correlation between the AMO and ISMR is found both in observations and models. However, instrumental records show that the relationship becomes non-significant or even of opposite sign after the mid-1990s, suggesting a weakening of the AMO-ISMR connection. The mechanism for the breakdown of the AMO-ISMR connection is investigated in the present work, and the results suggest that a substantial warming in the Indian-tropical western Pacific Ocean plays a role. The warming weakens the meridional gradient of tropospheric temperature between Eurasia and the indian Ocean, and reduces the meridional sea level pressure gradient between the Indian Subcontinent and Indian Ocean, weakening the Indian summer monsoon. Thus, warming in the Indian-tropical western Pacific Ocean seems responsible for the weakened connection between the AMO and ISM.展开更多
基金supported by the National Key Research and Development Program of China[grant number 2016YFA0601802]the National Natural Science Foundation of China[grant number41375085],[grant number 421004]the Strategic Project of the Chinese Academy of Sciences[grant number XDA11010401]
文摘Previous studies have shown that the Atlantic Multidecadal Oscillation （AMO） can play an important role in modulating the variabilityoflndian summer monsoon rainfall （ISMR） over a 50-60-yr timescale. A significant positive correlation between the AMO and ISMR is found both in observations and models. However, instrumental records show that the relationship becomes non-significant or even of opposite sign after the mid-1990s, suggesting a weakening of the AMO-ISMR connection. The mechanism for the breakdown of the AMO-ISMR connection is investigated in the present work, and the results suggest that a substantial warming in the Indian-tropical western Pacific Ocean plays a role. The warming weakens the meridional gradient of tropospheric temperature between Eurasia and the indian Ocean, and reduces the meridional sea level pressure gradient between the Indian Subcontinent and Indian Ocean, weakening the Indian summer monsoon. Thus, warming in the Indian-tropical western Pacific Ocean seems responsible for the weakened connection between the AMO and ISM.
