Comparative Analysis of the Atmospheric Intraseasonal Oscillation in Two Asian Monsoon Regions

The ECMWF daily reanalysis data (1961－2000）are used to study the differences of intraseasonal oscillation (ISO) between the South China Sea (SCS) and South Asia (SA) monsoon regions through the band-pass filtering for 30－60 days. The comparative analysis of the ISO in these two regions is made mainly from the structure and horizontal propagation including zonal propagation and meridional propagation. It is found that the vertical structure of ISO in the SCS tilts westward more obviously than that in SA and that the summer monsoon trough over the SCS is more powerful than that over SA. The meridional and zonal propagations of the ISO in the two monsoon regions in 1996 are compared as an example. It is shown that all of them propagate northward but the ISO over the SCS begins to propagate northward earlier and arrives at the lower latitude than that over SA; the northward propagating is relatively slow over the SCS; the zonal propagation of the ISO is obviously different over these two regions, before July the ISO propagates westward over the SCS while eastward over SA.