THE EXCITING MECHANISM OF TROPICAL INTRASEASONAL OSCILLATION TO EL NINO EVENT |
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| Authors: | Li Chongyin and Liao Qinghai |
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| Institution: | LASG, Institute of Atmospheric Physics, CAS, Beijing 100080;LASG, Institute of Atmospheric Physics, CAS, Beijing 100080 |
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| Abstract: | The data analyses indicated that the occurrence of EL Nino event is closely related to intraseasonal oscillation (ISO) in the tropical atmosphere: The intraseasonal oscillation is very strong in tile tropics (particularly over the equatorial western Pacific) prior to the occurrence of El Nino; But the ISO is evidently reduced and the quasistationary system is enhanced after the outbreak of El Nino. A simple air-sea coupled model study shows that the periodical self-excited oscillation can be produced in the air-sea-coupled system, but the pattern is different from the observed ENSO mode. When there is external (atmospheric) forcing with interannual time scale, a coupled mode, which looks like the ENSO mode, will be excited in the air-sea system. Synthesizing the results in data analyses and the theoretical investigation. the mechanism of ISO in the tropical atmosphere exciting the El Nino event can be suggested : The interannual anomalies (variations) of the tropical ISO play an important role in the exciting El Nino event through the air-sea interaction. |
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| Keywords: | Intraseasonal oscillation (ISO) in the tropical atmosphere interannual anomalies El Nino(ENSO) |
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