<p>The general circulation is primarily driven by surface temperature gradients. So, considering this, we explored the impact of Eastern Antarctica Warming (AW) on rainfall of prime summer monsoon months (July and August) (JA). As ENSO is a dominant mode of tropical variability in summer monsoon, to explicitly understand the AW effect, we removed the ENSO impact on Indian summer monsoon variables. June AW is significantly and negatively correlated to rainfall over India except the regions of Western coast and Eastern Central India. An East–west dipole rainfall pattern with positive/negative anomalies over eastern Asian countries/Indian mainland is observed. The wave trains that generated owing to the changes in June AW, persisted in June as well as JA and impacted the circulation patterns at both higher and lower levels. These fluctuations at lower levels slowly influenced the surface parameters like surface wind speed. The gradual response of ocean surface to the vigorous/frailer winds over Sub tropical/equatorial pacific region led to obstinate cold/warm SSTs (depicting a slowdown in ocean’s meridional overturning circulation) and eventually impacted the equatorial walker circulation in JA, causing subsidence over Indian monsoon region. Though the SST distribution over equatorial Indian and Pacific regions, enfeebled Walker circulation and deficit rainfall towards Indian mainland resemble El Niño type conditions, these changes are actually different from pure El Niño conditions in terms of magnitude and spatial distribution. The mean sea level pressure changes that appeared as a manifestation of vicissitudes in Hadley as well as walker circulations influenced the gradient between Eastern Equatorial Indian Ocean and Bay of Bengal and led to deficit/active rainfall over parts of India/eastern Asian countries. Thus, AW favoured/unfavoured the rainfall activity over Central eastern Indian regions/ Northwestern and Central Northeastern India regions (Especially fertile Upper middle Gangetic plains).</p>

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Antarctica warming induces alarming negative impact on Indian summer monsoon rainfall

  • V. S. Lakshmi Bhargavi,
  • Vadlamudi Brahmananda Rao,
  • Chennu Venkateswara Naidu

摘要

The general circulation is primarily driven by surface temperature gradients. So, considering this, we explored the impact of Eastern Antarctica Warming (AW) on rainfall of prime summer monsoon months (July and August) (JA). As ENSO is a dominant mode of tropical variability in summer monsoon, to explicitly understand the AW effect, we removed the ENSO impact on Indian summer monsoon variables. June AW is significantly and negatively correlated to rainfall over India except the regions of Western coast and Eastern Central India. An East–west dipole rainfall pattern with positive/negative anomalies over eastern Asian countries/Indian mainland is observed. The wave trains that generated owing to the changes in June AW, persisted in June as well as JA and impacted the circulation patterns at both higher and lower levels. These fluctuations at lower levels slowly influenced the surface parameters like surface wind speed. The gradual response of ocean surface to the vigorous/frailer winds over Sub tropical/equatorial pacific region led to obstinate cold/warm SSTs (depicting a slowdown in ocean’s meridional overturning circulation) and eventually impacted the equatorial walker circulation in JA, causing subsidence over Indian monsoon region. Though the SST distribution over equatorial Indian and Pacific regions, enfeebled Walker circulation and deficit rainfall towards Indian mainland resemble El Niño type conditions, these changes are actually different from pure El Niño conditions in terms of magnitude and spatial distribution. The mean sea level pressure changes that appeared as a manifestation of vicissitudes in Hadley as well as walker circulations influenced the gradient between Eastern Equatorial Indian Ocean and Bay of Bengal and led to deficit/active rainfall over parts of India/eastern Asian countries. Thus, AW favoured/unfavoured the rainfall activity over Central eastern Indian regions/ Northwestern and Central Northeastern India regions (Especially fertile Upper middle Gangetic plains).