A study of the effects of anomalous SSTs over the tropical Indian Ocean and the tropical Pacific on the establishment of the anomalous Philippine Sea anticyclone

Based on the NCEP/NCAR reanalysis data, the sea surface temperature (SST) data from the NOAA and the outgoing longwave radiation (OLR) from the NOAA2-CIRES, the influence of SST anomaly (SSTA) of the tropical Pacific and the tropical Indian Ocean on the process of the development and eastward passage of the tropical lowlevel anomalous anticyclone (LAAC) which eventually anchors in the Philippine Sea (named PSAC) is investigated in this paper. The results show that （1) The LAAC was developing in the Indian Ocean in earlier fall. The eastward passage of the LAAC appears to be the results from the horizontal asymmetry of moisture and temperature anomalies as well as the existence of the largescale divergent center over the maritime continent. The two conditions are significantly correlated with the SSTA over the tropical ocean and the SSTA evolvement. （2) For single El Ni?o o events and single positive Iudian Ocean Dipole (IOD) events, the distribution pattern and the SSTA evolvement benefit the formation of the horizontal asymmetry of moisture and temperature anomalies as well as the largescale divergence anomaly over the maritime continent. Compared to the El Ni?o events, the positive IOD events are much weaker with shorter duration. As the result, the PSAC is much weaker and has shorter lifecycle. （3) When an El Ni?o event occurring with a positive IOD event, the SSTAs over the two oceans and the divergent center over the maritime continent more avail the moving and development of the LAAC. As the result of the combined influence of positive IOD and El El Ni?o events, the PSAC was stronger and sustained for a longer time than those in the case of the single El Ni?o events or single positive IOD events.