Abstract:Based on the NCEP/CFSR reanalysis coupling data, the influences of MJO on the ENSO are investigated. The results show that intensities of MJO in the tropical Indian Ocean can affect the occurrence and development of the ENSO on the interannual and interdecadal time scales. Further analyses show that,the Westerly Wind Burst (WWB) over the equatorial central eastern Pacific, as the earlier stage signal of ENSO and the main way for MJO to influence ENSO,has significant sub-seasonal variations on the interannual time scale. Compared with the Walker circulation with the warm pool area over the equatorial western Pacific with climatological mean condition rising and the eastern Pacific sinking, the abnormal westerly after the positive phase of MJO moves eastward weakens the easterly at the low level and results in the upwelling sea water in the equatorial eastern Pacific. The weakening of the upwelling leads to rising sea surface temperature of the equatorial central eastern Pacific, which creating a favorable condition for the occurrence of ENSO. However, there was an obvious change on the ranges and strength of MJO around 1998 on the interdecadal time scale. The stronger MJO moved further eastward before 1998, causing more significant and frequent WWB events in the western Pacific, which corresponds to the strong ENSO under the Bjekness positive feedback mechanism on the interdecadal time scale. The situation after 1998 is the opposite.The influences of MJO on the ENSO in winter are more obvious in late winters on the interdecadal time scale. However, in the early winters, MJO intensifies increasingly with the Indian Ocean warming.