Impacts of two types of El Niño on the MJO during boreal winter

Abstract

The features of the MJO during two types of El Nino 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 Nino events, as compared to central Pacific (CP) El Nino events. First, the intensity of the MJO is weakened during EP El Nino winters from the tropical eastern Indian Ocean to the western Pacific, but enhanced during CP El Nino winters. Second, the range of the MJO eastward propagation is different during the two types of El Nino events. During EP El Nino winters, the MJO propagates eastwards to 120°W, but only to 180° during CP El Nino winters. Finally, the frequency in eight phases of the MJO may be affected by the two types of El Nino. Phases 2 and 3 display a stronger MJO frequency during EP El Nino winters, but phases 4 and 5 during CP El Nino winters.