Recorded presentation12.3
Moist teleconnection between tropical SST and south Asian monsoon
Prasanth Appukuttan Pillai, International Pacific Research Center, Honolulu, HI; and H. Annamalai
Deviating from tradition, the observed monsoon rainfall variability over India is classified into three categories, namely: (i) moderate (> 0.5 < 1.0 standard deviation); (ii) strong (> 1.0 < 1.5 standard deviation) and severe (> 1.5 standard deviation). Each of these categories' association with boundary forcing, in particular with tropical SST anomalies, are then examined. While anomalously strong and severe monsoon years are linked with equatorial Pacific SST variations associated with ENSO, the intensity of ENSO does not determine the intensity of monsoon rainfall. The moderate events have no association with ENSO. Due to limited samples from observations, the diagnostics is repeated with the 5-member ensemble simulation of the GFDL_CM2.1 20th century integrations spanning the period 1861-2000. Of the total 700-years analyzed, 20% strong and 15% severe monsoon years are identified. In the model, while most of the strong and severe years (80%) are associated with ENSO, regional SST anomalies over the Indo-Pacific warm pool also cause severe monsoon years. The severe monsoons associated with these tropical SST anomalies are investigated in detail. For severe monsoon category, the anomalies in monsoon characteristics are noted in late boreal spring, and they persist into fall. To understand the processes involved in the teleconnection, idealized ensemble simulations with the atmospheric component of CM2.1 are carried out. We perform moisture and moist static energy budgets in CM2.1 and AGCM integrations and note that the interaction of equatorial waves with moist physics is responsible for setting up the teleconnection.
Session 12, Air-Sea Interaction in the Indo-Pacific Region
Thursday, 30 September 2010, 3:30 PM-5:00 PM, Capitol AB
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