The relationship between ENSO and Indian Ocean Dipole was discussed by using the data set of sea temperature from Scripps Institute of Oceanography, the air temperature at 1000hPa from the NCEP reanalysis data and the Nino3 index from the Climate Prediction Center （CPC） of U.S.A. during the period from 1955 to 2001. The results show that there exists a Dipole on the maximum temperature anomalous level （MTAL） in the Indian Ocean, which close relates to ENSO in the Pacific Ocean. During El Nino periods there are good relationships between ENSO and Indian Ocean Dipole which maximum correlation occurring when ENSO leads by one month, but in La Nina periods the relationship is not so good. The distribution of Dipole in Indian Ocean is from northeast to southwest, which one （west） pole in 65°E - 75°E, 6°S - 10°S and the other in 85°E - 95°E, 2°N - 6°N, which is different from that defined by Saij. The correlation coefficients of Nino3 index with temperature anomalies in the west/east poles on the MTAL are over 0.4 - 0.15, respectively. It is a main sea temperature system in the tropical Indian Ocean. However, in the surface layer from sea surface to the depth of 20 m - 30 m there is no such a dipole with opposite sea temperature anomalies in the NE and SW of tropical Indian Ocean. The SSTA in the NE might be influenced by the sensible exchange process because the evolution of sea and 1 000 hPa air temperature anomaly time series of the NE of tropical Indian Ocean is quite similar except those during 1962 - 1963 and 1986. The periods of Indian Ocean Dipole are shorter than that of ENSO, and about 1 to 6-year.
Instead of using complicated general circulation models (GCMs), a simple semi-analytical model based on ray theory has been used to study energy evolution and ray path of Rossby waves in slowly varying mean flows. Our model yields similar results to those calculated from barotropic models, and also provides a chance to study Rossby waves in the slowly varying flows with both vertical and meridional shears. The model results show that upward Rossby waves can only grow in westerlies, and decay when further ascend. The baroclinic Rossky waves are restrained by the β effect in lower latitude. In the westerly jet with meridional and vertical shears, the barotropic Rossby waves originated from south of the westerly jet, and these can grow while propagating upper-northward. The baroclinic Rossby waves originated from north of the westerly jet and can grow while propagating upward and southward. Such a semi-analytical model provides a simple forecasting tool to allow study of the local weather anomalies to the heating/topography forcing associated with the global warming.
The characteristics of continental shelf waves forced by nonlinear continental shelf topography are studied with a shallowwater model.Results show that there are two topographic Rossby waves and two inertia gravity waves.The northward propagating topographic Rossby wave couples with the inertia gravity wave into an unstable wave in the long wave band.When the continental slope is increased,the topographic Rossby wave still couples with the inertia gravity wave into an unstable wave,but the frequency decreases.In the South China Sea(SCS),the western boundary can develop an unstable wave because of topographic forcing,nonlinear conditions,and increasing amplitude.It is possible that the unstable wave develops into a vortex.In observations,the SCS has a strong western boundary current and abundant mesoscale vortice.There is a strong relationship between the emergence,disappearance,and movement of the circulation's multi-eddy structure and the seasonal evolvement of the SCS's circulation.This article shows a possible mechanism for the formation of vortices in the SCS.
The Pacific Ocean circulations were simulated based on the global warming from 1960 to 1999 by using the Non-Boussinesq POP model and the data of wind stress and temperature at 1 000 hPa from the NCEP. The results show that the circulation in the tropical Pacific Ocean was weakening during the past 40 years. The heat transported to the tropical western Pacific Ocean coast by the north equatorial current and the heat transported to middle and high latitudes in the southem hemisphere by the south equatorial current decreased with time due to the global warming, while the heat transported to middle and high latitudes in the northern hemisphere by the north equatorial current increased with time due to the global warming.
