A STUDY ON THE RELATIONSHIP BETWEEN THE ANOMALY OF SUBTROPICAL HIGH OVER THE WESTERN PACIFIC AND THE HEAVY FLOODING IN YANGTZE RIVER VALLEY IN 1998

The anomal ousactivity of subtr opical high over the western Pacific is studied during the summer of 1998,when the heavy flooding occurred in the Yangtze River region.The paper presents the influence of El Niño event in that period on the subtr opical high anomaly and the relationship between the distributions of apparentheat source Q1 and moist sink Q2 and the anomal oussubtropical high.The main charact eristics of subtropical high in that summer are given including its seasonal position,strength and the relation to the precipitation in the Yangtze River Valley.The main coupled mode between SST and subtr opical current revealed by SVD analysis shows that if the distribution of SST Apresents an El Niño pattern and its streng th decays from preceding winter to summer,the strength of subt ropical high in the western Pacific in the summer would be stronger and located at the lower latit udes,especially at its western part.The ITCZ at the southern side would be comparatively weaker.The 1997-1998 El Niño event was decaying from winter to summer,and the features of circulation around the subtro pical high are similar to that mode.There fore the influence of 1997-1998 El Niño on the anomalous subtropical high is very clear.The vertical circul ations have shown an anomalous upward flow over the eastern equatorial Pacific,and a down ward current over the western Pacific.The dist ribution of Q1 and Q2 may well describe the position and intraseasonal variation of the subtropical high,there fore explain the second period of Meiyu in the end of July in 1998.