The present session also suggests strongly the need of suitable process studies to understand more about the barrier layers, ISO, IOD, IT and subtropical coupled disturbances. In model studies, the present session suggests that
i) AGCMs should resolve ISO,
ii) OGCMs should resolve barrier layers, right phases of IOD, and
iii) CGCMs should resolve IOD.
(Prepared by T. Yamagata)
2nd Session: Southern Ocean Variability (Chairs: W. White and T. Motoi)
We had three speakers, T. Motoi (FRSGC/Japan), P. G. Baines (CSIRO/Australia) and W. B. White (SIO/USA.).
Previous studies on Antarctic Circumpolar Wave (ACW) were reviewed. The ACW was found to be a large scale interannual climate signal intrinsic to the Southern Ocean, with covarying SST and SLP anomalies of zonal wavenumber 2 propagating eastward around Antarctica at approximately 45 degrees of longitude per year. A coupled model simulation of the ACW finds it penetrating deeply into the upper ocean, characterized by barotropic circulation anomalies.
It was proposed that the ACW can be initiated by a connection between the ACW and the El Nino-Southern Oscillation, through atmospheric teleconnection in the form of the Pacific South American pattern. The four-year periodicity of ENSO in recent years then gives the zonal wavenumber 2 pattern. The propagation of covarying SST and SLP anomalies around the Southern Ocean indicates that coupling maintains the magnitude of the ACW and may significantly influence its phase speed. The influences of ACW on climate variations over Australia were shown, with the warm (cool) SST phase of the ACW associated with more (less) precipitation over Australia. The slow eastward propagation of the ACW was used to forecast Australia precipitation from one year to the next over the past 50 years with significant skill.
An oceanic teleconnection transmits ACW signals in the Southern ocean into the tropical Indian and Atlantic oceans. This offers the possibility for an oceanic teleconnection between ACW and Indian Ocean Dipole. The role of sea ice in the ACW phenomenon was suggested as one of the important problems for future study.
(Prepared by T.Motoi et al)
