THE POSITION VARIATION OF THE WEST PACIFIC SUBTROPICAL HIGH AND ITS POSSIBLE MECHANISM

Using NCEP/NCAR daily reanalysis data and SCSMEX data, an investigation is carried out ofthe relationship between the position variation of the west Pacific subtropical high (WPSH) and the apparentheating in June 1998 based on the complete vertical vorticity equation. It is found that the non-adiabatic heatingplays an important role in the position variation of WPSH. In comparison with climatic mean status, the verticalchange of non-adiabatic heating is stronger in the north side of WPSH in June 1998, but weaker in the south sideof WPSH. The anomalous non-uniform heating induces anomalous cyclonic vorticity in South China, areas to thesouth of the Yangtze and its mid-lower valleys, but anomalous anticyclonic vorticity in the Indo-China Peninsulaand South China Sea areas lead to the more southward position of WPSH than the mean.

THE VARIATION OF THE SPRING PRECIPITATION IN GUANGZHOU AND ITS PRECURSORY SIGNALS

Guangzhou spring rainfall mainly exhibits interannual variation of Quasi-biannual andinterdecadal variation of 30 yrs, and is in the period of weak rainfall at interdecadal time scale.SST anomalies (SSTA) of Nino3 are the strongest precursor of Guangzhou spring rainfall. Theyhave significant positive correlation from previous November and persist stably to April. Nino3SSTA in the previous winter affects Guangzhou spring rainfall through North Pacific subtropicalhigh and low wind in spring. When Nino3 SSTA is positive in the previous winter, springsubtropical high is intense and westward, South China is located in the area of ascending airflow atthe edge of the subtropical high, and water vapor transporting to South China is intensified byanticyclone circulation to the east of the Philippines. So Guangzhou spring rainfall is heavy. WhenNino3 SSTA is negative, the subtropical high is weak and eastward, South China is far away fromthe subtropical high and is located in the area of descending airflow, and water vapor transportingto South China is weak because low-level cyclonic circulation controls areas to the east of thePhilippines and north wind prevails in South China. So Guangzhou spring rainfall is weak andspring drought is resulted.

RELATIONSHIP BETWEEN WEST PACIFIC SUBTROPICAL HIGH AND ENSO AND ITS INFLUENCE ON RAINFALL DISTRIBUTION OF RAINY SEASON IN FUJIAN

Relationship between the variations of West Pacific subtropical high indices in the summer half of the year and preceding SST in North Pacific was examined based on a data set of 1951 2000. The correlation between the subtropical high indices and preceding SST in the equatorial East Pacific was the strongest among the others, and has great persistency from last autumn to spring. It is indicated that ENSO events appeared about six months earlier than the change of the subtropical high activities, and the subtropical high intensities enhanced (weakened) and western ridge point was westward (eastward) in the year of El Nino (La Nina) events. It was also observed that there were similar interdecadal oscillation and abrupt variations between Nino3 SST, subtropical high intensities and rainfall of rainy season in Fujian. Therefore, experiments were made on rainfall distribution of rainy season in Fujian. The results showed that the distribution was directly affected by the subtropical high activities, pronouncedly caused by ENSO effect.