The Climatological Study Of The Intraseasonal Oscillation Of The Air-sea System

In terms of diagnostic analysis chiefly, including of Lanczos filter, Single Value Decomposition(SVD),CEOF, composite and correlation analysis etc., and numerical modeling, the temporal and spatial characteristics of the intraseasonal oscillation(MJO) of the air-sea system and the causes are investigated in this paper. The main results are as follows.1) The centers of the strong OLR MJO as found in the tropical Indian ocean and the western Pacific warm pool are observed in any one of the four seasons; The MJO are stronger in the boreal winter and spring than in the boreal summer and autumn and move southward and northward with season; high climatic SST is the conditions for strong OLR MJO. The tropical eastern Pacific (for the whole year), northwest Pacific (for the boreal spring, summer and autumn) and southwest Pacific (for the austral summer around ) are the strong MJO regions of SST with the conditions of shallow climatic mixed layer depth.2) The OLR MJO intensity anomaly for the four key areas of the Pacific, namely, the tropical western Pacific, the middle and eastern Pacific, the northwest Pacific and the southwest Pacific, is significantly and positively related to the local SSTA. With the exception of the tropical western Pacific of large mld .there is negative correlation relationships between the anomaly of the SST MJO intensity and that of the mld in the other three regions in the seasons of the climatic small mld Thus the causes of climatic and anomalous characteristics of atmospheric MJO are related to SST identically, and the corresponding features of SST MJO are related to mld,3) ENSO is the strongest sign and can lead to the distinct SST and mld anomaly, hence the intensity anomaly of the air-sea system inevitably takes place during the ENSO. During the El Nino(La Nina) events, the negative(positive) SST anomaly occurs and the corresponding the OLR MJOintensity weakens (enhances) in the tropical western Pacific; at the same time, the positive(negative) surface westerly anomaly leads to positive(negative) mld anomaly, and the corresponding SST MJO intensity weakens (enhances) in the equatorial eastern Pacific,4) The interdecadal variation of the atmospheric MJO intensity took place distinctly in 1970s in the tropical western , northwest and eastern Pacific, with the stronger intensity in the former than the back stage, and the interdacadal variation of SST is its cause.5) The features of the OLR and velocity potential(x) MJO spreadingeastward, northeastward(WNP) and southeastward (WSP)are researched on the climatic and interannual scale. It is shown that OLR spread eastward more clearly in the eastern hemisphere, and the x is persistently spread eastwardin both hemisphere; The interannual variability of the spread of MJO is evident, with the intensity weakening during El Nino events and sometimes spreading westward in individual years. The WSP is more important than the WNP. The spread features of SST MJO are not clearly.6) The correlation relationships of the MJO of daily 10m-wind ( v ) fields with that of SST fields are investigated by time-lagged SVD method in the north Pacific, south Pacific and the tropical eastern Pacific, and the basal process of v and SST MJO obtained in the three areas, which is a negative feedback process drived by drift and sensible heat under the conditions of shallow mld, is probably the maintaining mechanism.