A STUDY ON THE CHARACTERISTICS OF THE LOW-FREQUENCY OSCILLATION OVER WEST PACIFIC AND ITS RELATIONS WITH SUBTROPICAL HIGH AND TYPHOONS

In this paper, by using the daily wind data from May 1 to September 30,1985 at the level of 850hPa, the geographical distribution of the low-frequency oscillation (LFO)(around 40 days) over west Pacific and its propagation features are analysed. The result shows that besides the ITCZ region, there exist other two regions where the 30-50d oscillation dominates. One is over the northwest Pacific Ocean corresponding with the subtropical High, and the other is over Australian continent related to the cold High in Southern winter. From the time-continuous LF weather maps, it is found that the LF cyclones and anticyclones occur alternately in regions of large variance of 30-50d filtered wind, and propagate in rather regular patterns. Also, there exists a good relationship between LF cyclone (anticyclone) and the activity of typhoon (subtropical High).While propagating southward, the LFO in Northern Hemisphere (NH) can trigger the LF wave in Southern Hemisphere (SH),in turn.the LF wave in SH can influence the activity of typhoon in NH by changing the across equatoral flow.