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Can El Nino-Southern Oscillation (ENSO) events modulate intraseasonal oscillations of Indian summer monsoon?

Joseph, S and Sahai, AK and Chattopadhyay, R and Goswami, BN (2011) Can El Nino-Southern Oscillation (ENSO) events modulate intraseasonal oscillations of Indian summer monsoon? Journal of Geophysical Research D: Atmospheres, 116 (20).

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Prediction of interannual variability (IAV) of Indian summer monsoon (ISM) rainfall is limited by "internal" dynamics, and the monsoon intraseasonal oscillations (MISOs) seems to be at the heart of producing internal IAV of the ISM. If one could find an identifiable way through which these MISOs are modulated by slowly varying "external" forcing, such as El Niño-Southern Oscillation (ENSO), the uncertainty in the prediction of IAV could be reduced, leading to improvement of seasonal prediction. Such efforts, so far, have been inconclusive. In this study, the modulation of MISOs by ENSO is assessed by using a nonlinear pattern recognition technique known as the Self-Organizing Map (SOM). The SOM technique is efficient in handling the nonlinearity/event-to-event variability of the MISOs and capable of identifying various shades of MISO from large-scale dynamical/thermodynamical indices, without providing information on rainfall. It is shown that particular MISO phases are preferred during ENSO years, that is, the canonical break phase is preferred more in the El Niño years and the typical active phase is preferred during La Nia years. Interestingly, if the SOM clustering is done by removing the ENSO effect on seasonal mean, the preference for the break node remains relatively unchanged; whereas, the preference reduces/vanishes for the active node. The results indicate that the El Niño-break relationship is almost independent of the ENSO-monsoon relationship on seasonal scale whereas the La Nia-active association seems to be interwoven with the seasonal relationship.

Item Type: Article
Additional Information: Copyright of this article belongs to American Geophysical Union.
Uncontrolled Keywords: Active node; Indian summer monsoon; Interannual variability; Intraseasonal oscillations; Non-Linearity; Nonlinear pattern; Seasonal mean; Seasonal prediction; Seasonal scale; Self organizing; SOM clustering, Atmospheric pressure; Climatology; Conformal mapping; Forecasting; Nickel compounds; Pattern recognition; Rain; Tropical engineering, Atmospheric thermodynamics, El Nino-Southern Oscillation; La Nina; nonlinearity; rainfall; temporal variation; thermodynamics; uncertainty analysis, Nia
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 19 Jul 2014 07:16
Last Modified: 19 Jul 2014 07:16

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