Impacts of Two Types of El Niño on the MJO during Boreal Winter

The features of the MJO during two types of El Niño events are investigated in this paper using the daily NCEP-2 reanalysis data, OLR data from NOAA, and Real-time Multivariate MJO index for the period 1979-2012. The results indicate that the MJO exhibits distinct features during eastern Pacific (EP) El Niño events, as compared to central Pacific (CP) El Niño events. First, the intensity of the MJO is weakened during EP El Niño winters from the tropical eastern Indian Ocean to the western Pacific, but enhanced during CP El Niño winters. Second, the range of the MJO eastward propagation is different during the two types of El Niño events. During EP El Niño winters, the MJO propagates eastwards to 120°W, but only to 180° during CP El Niño winters. Finally, the frequency in eight phases of the MJO may be affected by the two types of El Niño. Phases 2 and 3 display a stronger MJO frequency during EP El Niño winters, but phases 4 and 5 during CP El Niño winters.