The interrelationships among the 700mb zonal wind in the tropics, the sea surface temperature (SST) in the tropical Indian and Pacific Oceans, and the sea water temperature (SWT) in the tropical western Pacific are discussed on a characteristic interannual time scale. The interannual variability of the main thermocline in low latitudes along 137°E longitude line is reflected primarily on the quasi-biennial oscillation (QBO) time scale. To investigate its physical process, each dominant QBO mode propagating eastward is deduced by applying the complex EOF analysis to monthly mean SST and 700mb tonal wind data over tropical Indian and Pacific Oceans. The QBO mode of the 700mb zonal wind propagates eastward with uniform phase speed. On the other hand, the QBO mode of SST does not propagate with uniform phase speed and a marked phase difference is observed at the area around 150-160°E, where the zonal wind anomalies at 700mb level have the largest amplitudes. Thus, the QBO mode of tropical SST does not always propagate in parallel with that of the tropical troposphere and it is suggested that the tropical tropospheric QBO mode propagating eastward from the Indian Ocean brings about the remarkable phase shift of SST anomalies around 150-160°E. Since the SWT anomalies located in the main thermocline fluctuate in phase with those in the near surface layer (0-50m depth), it is inferred that these variations, which are influenced by the accumulation and release of warm water east of the Philippines, result from the dynamic response of the ocean to the wind stress with the QBO variability.
All Science Journal Classification (ASJC) codes
- Atmospheric Science