해양-대기 접합모형에서 평균장의 장주기 변동성에 따른 ENSO 변동성

Abstract

In the light of the results of the CGCM vertical mode decomposition, we test if the non-linearities associated to change in the baroclinic mode energy distribution can lead to coherent ENSO modulation in the ICM. The results indicate that consistent rectification of the interannual variability (ENSO timescales) by the decadal variability associated to changes in the oceanic mean states takes place. The magnitude and characteristic (phase relationship between ENSO modulation and decadal mode of thermocline depth) of this rectification depend however on the climatological state prescribed in the ICM. In particular, the seasonal cycle as simulated by the CGCM amplifies the zonal advective feedback in the western Pacific, which tends to mask the rectified effect of changes in mean stratification. In the CGCM, the atmospheric response associated to the ENSO modulation forces through Ekman pumping the decadal mode of thermocline depth with a peak variability in the South-Western Pacific. A tropical mechanism for producing ENSO modulation is proposed, which conceals both the rectified effect associated to non-linearities of the equatorial wave dynamics and the tropical decadal mode of thermocline depth arising from Ekman pumping anomalies located in the central Pacific, south of the equator.