VARIATION OF THE WEST PACIFIC SUBTROPICAL HIGH AND ITS CHANGEABLE RELATIONSHIP WITH SST UNDER THE BACKGROUNG OF COLD OR WARM CLIMATE FLUCTUATION IN THE RECENT 60 YEARS
Using subtropical high index data from the National Climate Center, NCEP/NCAR reanalysis data and the NOAA sea surface temperature data and based on the Gaussian filter, moving average and the methods of correlation and synthesis analysis,this study discusses the West Pacific subtropical high (WPSH) and possible reasons for its variation under the background of cold or warm climate fluctuation. The results show that for the climate fluctuation in the recent 60 years,the most significant change of WPSH is the expanding of the area. At the same time,the intensity of WPSH has intensified,the westernmost ridge point has extended westward, and the southern boundary has expanded. The interannual variability of all WPSH indexes has increased. The intensity and the westernmost ridge point of WPSH are consistent with global warming,but the ridge line is different. The intensity and its interannual variability of WPSH intensified in the late 1980s, the westernmost ridge point has extended westward in the early 1990s and its interannual variability has intensified in the late 1990s. The ridge line has experienced shifts of north,south and then north again and its interannual variability has also intensified in the late 1990s. As the climate warming, the positive correlation between the equatorial central-eastern Pacific sea surface temperature (SST) in winter and the intensity of WPSH was weakened,but the westward extension of west ridge point was enhanced and expanded; The positive correlation between the North Pacific SST in winter and the southward of ridge line was weakened,but the westward extension of west ridge point was enhanced; The negative correlation between the Tropical Western Pacific SST in winter and the intensity of WPSH was increased, and the westward extension of the ridge was strengthened. In the warmer climate period, with the strengthening and southward shift of Hadley circulation and the weakening of Walker circulation's rising branch, the summer WPSH have strengthened, expanded, and shifted to the south.