Sea surface temperature in the South China Sea - an index for the Asian monsoon and ENSO system

Interannual variability of the sea surface temperature anomalies (SSTA) over the South China Sea (SCS) is recognized as an index for the Asian monsoon and ENSO system because of its special geographical location for that system. The following results are obtained by the statistical analysis of the observational data. (1) In the northern winter, the SCS SSTA are quite sensitive to the longitudinal shift of global wind anomalies associated with the equatorial Pacific SSTA. This fact is related to that the SCS SSTA and the neighbor SSTA have strong biennial oscillation. (2) When the global wind anomalies are shifted eastward in the winter (BO-type years), the tropical eastern Pacific SSTA tend to change in the following spring. On the other hand, when those wind anomalies are shifted westward (LF-type years), the eastern Pacific SSTA tend to be maintained through the year. The associated differences between the BO and LF-type years are found in the seasonal change of the low-level tropical wind anomalies from the preceding summer through winter. (3) The northern summer SCS SSTA seem to be controlled by in-situ low-level wind anomalies. Further more, easterly anomalies over South Asia and the tropical western Pacific and westerly anomalies over East Asia are found in the lower atmosphere for the positive SCS SSTA. It is also shown that the summer SCS SSTA have a statistical relationship with the equatorial central Pacific SSTA in the preceding winter. This fact suggests a relationship between the summer Asian monsoon and the winter phase of ENSO.