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Pre-onset land surface processes and 'internal' interannual variabilities of the Indian summer monsoon

Saha, SK and Halder, S and Kumar, KK and Goswami, BN (2012) Pre-onset land surface processes and 'internal' interannual variabilities of the Indian summer monsoon. Climate Dynamics, 36 (11-12). pp. 2077-2089.

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It is proposed that, land-atmosphere interaction around the time of monsoon onset could modulate the first episode of climatological intraseasonal oscillation (CISO) and may generate significant 'internal' interannual variation in the Indian summer monsoon rainfall. The regional climate model RegCM3 is used over Indian monsoon domain for 27 years of control simulation. In order to prove the hypothesis, another two sets of experiment are performed using two different boundary conditions (El Niño year and non-ENSO year). In each of these experiments, a single year of boundary conditions are used repeatedly year after year to generate 'internal' interannual monsoon variability. Simulation of monsoon climate in the control model run is found to be in reasonably good agreement with observation. However, large rainfall bias is seen over Arabian Sea and Bay of Bengal. The interannual monsoon rainfall variability are of the same order in two experiments, which suggest that the external influences may not be important on the generation of 'internal' monsoon rainfall variability. It is shown that, a dry (wet) pre-onset land-surface condition increases (decreases) rainfall in June which in turn leads to an anomalous increase (decrease) in seasonal (JJAS) rainfall. The phase and amplitude of CISO are modulated during May-June and beyond that the modulation of CISO is quite negligible. Though the pre-onset rainfall is unpredictable, significant modulation of the post-onset monsoon rainfall by it can be exploited to improve predictive skill within the monsoon season.

Item Type: Article
Additional Information: Copyright of this article belongs to American Geophysical Union.
Uncontrolled Keywords: annual variation; boundary condition; climate modeling; climate oscillation; computer simulation; El Nino-Southern Oscillation; hypothesis testing; land surface; monsoon; numerical model; prediction; rainfall; regional climate; weather forecasting, Arabian Sea; Bay of Bengal; India; Indian Ocean
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 28 Oct 2014 09:53
Last Modified: 28 Oct 2014 09:53

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