A preliminary analysis on the relationship between the South China Sea summer monsoon onset and the upper heat content during the previous period in this region

Based on the monthly heat content and sea temperature datasets over the South China Sea (SCS) from January 1980 to December 2007, the temporal and spatial distribution characteristics of the heat content over SCS and its relationship with the onset of the summer monsoon(SCSM) was analyzed, after that, the possible contributions to the anomalous onset times of SCSM was further explored as well. It is showed that the main area of the upper layer heat content changes is located over the south central SCS (8°~16°N,110°~120°E), and the strongest signal of the heat content changes is kept in the subsurface (100~200 m) over the SCS. Compared with the early onset monsoon years, the features of the winter-spring heat content over the SCS holds the opposite polarity during the late onset years. The early (late) onset of the SCSM is accompanied by the positive (negative) heat content anomalies during the previous winter-spring except for December. Furthermore, it is also pointed out that the negative correlation coefficient peaks when the heat content anomalies lead the onset of the SCSM by 1~5 months, especially when the heat content anomaly is fixed in the previous March. Thus, the heat content in March over the south central SCS is a good premonitory signal for the onset of the SCSM. The positive (negative) heat content anomalies over the SCS as well as the positive (negative) upper ocean heat anomalies, which increase (decrease) the temperature gradient between ocean and land before the onset of the SCSM, are conducive to the early (late) onset of the SCSM eventually.