Abstract
Abstract The processes for the coupled tropospheric biennial oscillation involving the Indian monsoon and El Nino–Southern Oscillation (ENSO) are studied through composites of sequential wet monsoon/La Nina year followed by dry monsoon/El Nino year using observations and outputs from the Center for Ocean–Land–Atmosphere Studies (COLA) interactive ensemble coupled general circulation model. The previous composites emphasize the role of ENSO in the monsoon transition but do not exclude the possible role of factors other than ENSO. It is found that the central eastern equatorial Pacific sea surface temperature (SST) anomalies can affect the Indian monsoon transition by two processes: (i) a shift of large-scale east–west circulation across the equatorial Indian–Pacific Oceans; and (ii) a Rossby wave–type response over the eastern north Indian Ocean–western North Pacific. The former provides the low-level anomalous moisture convergence (divergence) that preconditions the atmosphere for a wet (dry) Indian monso...
Published Version
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