Code 613.1 Branch Seminar: C.-H. Sui

Institute of Hydrological Sciences, National Central University
I will briefly discuss my recent research in hydroclimate in East Asia, and then focus on the following research on climate oscillations that affect weather and climate in East Asia. The Western edge of North Pacific Subtropical High (WNPSH) in summer exhibits pronounced interannual variability which is well represented by a WNPSH index as the June-July-August mean 500hPa geopotential height anomaly averaged within the region (120-140E, 10-30N). A spectral analysis of the index calculated using NCEP/NCAR Reanalysis monthly data reveals two significant spectral peaks at 2-3 years and 3-5 years. The 3-5 years oscillations of WNPSH occurred in the period of 1965 to 1992. This is characterized by warm SSTAs in the central and eastern equatorial Pacific persisting from the preceding winter to the summer of high WNPSH index, and accompanied by a strong descending motion in the western equatorial Pacific which migrates southeastward from preceding winter to summer. The 3-5 years oscillations of WNPSH appear to be caused by the SST and related diabatic heating associated with ENSO events in the period of 1965 to 1992 that have relatively longer life cycle. The 2-3 years oscillations are most evident after 1978. It is characterized by warm SSTA in the tropical western Pacific, ascending motion over the maritime continent where deep convection is zonally aligned south of the equator, and descending motion in the center of the WNPSH. The above features are accompanied by weakening warm SSTAs from the preceding winter to cold SSTAs in summer of high WNPSH index in the Central-Eastern Pacific. It appears that the 2-3 years oscillations of WNPSH is a result of quasi-biennial change of SST in the western Pacific - maritime continent region.