Monsoon Variability


Extended Range Predictability of Monsoon Intra-seasonal Variability (Active/ Break Monsoon Spells) is being investigated. It is found that the potential predictability of both active and break spells have undergone a rapid increase during the recent three decades. Role of stratiform rainfall in modifying the northward propagation of monsoon intra-seasonal oscillation is studied. An analysis of daily rainfall over India during 1951-2007 reveals an increased duration and frequency of monsoon breaks over the subcontinent. While noting that the increasing trend of break monsoon condition is consistently related to changes in large sale monsoon circulation and vertically integrated moisture transport, the findings point to the role of sea surface temperature (SST) warming trend (0.015°C per year) in the tropical eastern Indian Ocean in inducing anomalous changes favorable for the increased propensity of monsoon breaks.

Understanding the links between the variation of the Indian monsoon and the variation of the atmospheric convection over the equatorial Indian Ocean with the analysis of the observations is crucial for the evolving circulation changes. In the first three weeks of June 2009, there were no northward propagations across the Bay. Also, no low pressure systems were generated over the head Bay and naturally, the westward propagation of such systems across the Indian monsoon zone, which is characteristic of the onset phase of the monsoon, did not occur. Consequently, there was a massive deficit of (48%) in the all India rainfall in June 2009. The El Nino induced Indian Ocean winter warming is significant in the following winter and spring and persists for the summer as well.

The basin scale deep warming in the west is associated with the local IOD forcing rather than the remote El Nino forcing. Indian Ocean warming induced anomalous climatic effects in Asia, Africa and NW Pacific.

Last Updated On 05/14/2014 - 16:57
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