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By using the upper-wind data from July 1980 to June 1983,the variations of the low-frequency oscillation(LFO)in the atmosphere before and during 1982 El Nino have been investigated.Before the El Nino,the LFOpropagates from west to east over the equator of the Eastern Hemisphere and from east to west over 20°N.The eastward propagating LFO over the equator consists of zonal wavenumber 1 propagating eastward andzonal wavenumber 2 with a character of stationary wave.The oscillation of zonal wavenumber 2 can modulatethe oscillation strength.After the onset of the El Nino,the propagating directions of the LFO over the equatorand 20°N of the Eastern Hemisphere change to be westward and eastward,respectively.The LFO over thewestern Pacific weakens rapidly and one coming from middle and high latitudes propagates to the equator.From the phase compositions of streamline fields for the zonal wavenumber 1 of equatorial westward propa-gatirg LFO,it is found that the atmospheric heat source in the equator of the eastern Pacific(EEP)excites aseries of the equatorial cyclones and anticyclones which move northward and westward and form the westwardpropagating LFO over the equator.With the wavelength of 20000km,this kind of equatorial wave is similarto the mixing Rossby-gravity wave.In its westward and northward movement,the circulation in East Asiais modified.This may be the mechanism of the influence of El Nino on the climate of China.
By using the upper-wind data from July 1980 to June 1983, the variations of the low-frequency oscillation (LFO) in the atmosphere before and during 1982 El Nino have been investigated. Before the El Nino, the LFO propagates from west to east over the equator of the Eastern Hemisphere and from east to west over 20 ° N. The eastward propagating LFO over the equator consists of zonal wavenumber 1 propagating eastward and zonal wavenumber 2 with a character of stationary wave. The oscillation of zonal wavenumber 2 can modulate the oscillation strength . After the onset of the El Nino, the propagating directions of the LFO over the equatorand 20 ° N of the Eastern Hemisphere change to be westward and eastward, respectively. The LFO over the western Pacific weakens rapidly and one coming from middle and high latitudes propagates to the equator. From the phase compositions of streamline fields for the zonal wavenumber 1 of equatorial westward propa-gatirg LFO, it is found that the atmospheric heat source in the equator of the eastern Pacific (EEP) excites a series of the equatorial cyclones and anticyclones which move northward and westward and form the westwardpropagating LFO over the equator. By the wavelength of 20000km, this kind of equatorial wave is similarto the mixing Rossby-gravity wave. In its westward and northward movement, the circulation in East Asiais modified. This may be the mechanism of the influence of El Nino on the climate of China.