Evolution features of MJO associated with ENSO events

Whether there is an independent component of MJO associated with El Niño Southern Oscillation (ENSO) is investigated using Xie-Arkin precipitation and NCEP reanalysis pentad data. The analysis tool employed here is the cyclostationary empirical orthogonal function (CSEOF) technique. As a result of the analysis, the evolution of the precipitation pattern for the Asian-Pacific domain is found to consist of annual cycle, an MJO component of which the interannual variation is almost the same as the Southern Oscillation (SO) and other MJO components which evolve independently of SO. The former MJO becomes stronger and attains maximum amplitude over the Indian Ocean and the western Pacific during the mature stage of ENSO due to an intensified zonal circulation change. Positive MJO anomalies passing through the Indian continent during summer are found to be important because they tend to strengthen the onset of Indian summer monsoon prior to an ENSO warm event. In the winter of El Niño years, convective anomalies associated with MJO, in general, propagate further eastward in the equatorial Pacific. The expansion of warm pool and the strengthening of westerly anomalies favor stronger surface wind convergence and the eastward penetration of MJO activity at 40-50 day intraseasonal period during El Niño mature stage.