Relationship between summer monsoon outbreak and upper-ocean heat content anomalies over the South China Sea

In this paper,various datasets are used to analyze the relationship between the South China Sea summer monsoon(SCSSM) and the SCS upper-ocean heat content(SCSHC).These datasets include SODA(Simple Ocean Data Assimilation) monthly-mean ocean temperature from 1958 to 2007,NCEP / NCAR reanalysis monthly-mean data from 1958 to 2008,and monthly-mean OLR(Outgoing Longwave Radiation) data from NOAA satellites from 1974 to 2008.It is found that the onset of the SCSSM is negatively correlated to the SCSHC in the previous winter,i.e.,the anomalously high(low) SCSHC in winter is corresponding to the early(late) outbreak of SCSSM in the following year.It is also found that the characteristics of OLR,geopotential height,and atmospheric circulation during the previous winter are consistent with the SCSHC.When the SCSHC is higher(lower) in winter,the OLR over regions from the eastern equatorial Indian Ocean to the SCS and the east of Philippines shows a negative(positive) anomaly,and the atmospheric circulation is characterized by positive(negative) anomaly of he Walker circulation and the Hadley circulation.In the following early spring(March April),the geopotential height at 500 hPa shows negative(positive) anomaly over the western Pacific Ocean(WPO),indicating that the subtropical high is weakened(strengthened) that is favorable(unfavorable) for the early outbreak of the SCSSM.The SCS and the WPO warm pool heat content anomalies could lead to large-scale circulation anomalies over the region through convection activities,which further influence the SCSSM onset.The difference in affecting the SCSSM onset between SCS and WPO is that the SCSHC anomalies may stimulate locally the Hadley circulation anomalies through convection,which will inhibit the northward extension of the southwesterly monsoon and affect the outbreak of the SCSSM.