Activities of Low-Frequency Waves in the Tropical Atmosphere and ENSO

ENSO, particularly the occurrence of ENSO is still an important research object in climatic variation. Using the ECMWF data, the relationship between ENSO and the activities of low-frequency waves in the tropical atmosphere is analyzed in this paper. It is shown that the occurrence of ENSO is closely related to the intraseasonal oscillation and the quasi-stationary waves (the period > 90 days) in the tropical atmosphere. Associated with the occurrence of El Nino event, the kinetic energy of low-frequency waves has obvious varia?tion: the kinetic energy of atmospheric intraseasonal (30-60 days) oscillation (ISO) decreases abruptly and the kinetic energy of quasi stationary waves increases abruptly. Moreover, the ISO and quasi-stationary waves propagate eastward clearly corresponding to El Nino; but they clearly propagate westward in La Nina cases.