中南半岛与南海热力差异对南海季风爆发的影响

Effects of the thermal contrast between Indo-China Peninsula and South China Sea on SCS monsoon onset.

利用1958—1998年NCEP/NCAR再分析资料和1975—1998年OLR资料,分析了中南半岛与南海热力差异的季节和年际变化特征,以及这种热力差异对南海季风爆发的影响。结果表明,中南半岛与南海热力差异存在明显的季节变化,从第3候开始,感热加热的作用使中南半岛地表温度高于南海并一直持续到第25候,之后,中南半岛与南海热力差异发生逆转,这种逆转是由于第22—23候出现在中南半岛的对流及降水造成中南半岛地表温度降低所致。进一步研究指出,中南半岛与南海热力差异的上述季节变化特征还表现出显著的年际差异,这种年际差异对南海季风的爆发有着重要影响。首先,上述热力差异的逆转是南海季风爆发的一个必要条件:1958—1998年,逆转时间均早于(或等于)南海季风爆发时间;其次,中南半岛地表温度高于南海的持续时间与南海季风爆发日期之间呈显著正相关,即中南半岛地表温度高于南海的时间越早、转为低于南海的时间越迟,则南海季风爆发越迟。

By using 1958 - 1998 NCEP/NCAR reanalysis data and 1975 - 1998 OLR data, the seasonal and interannual variations of the thermal contrast between Indo-China Peninsula （ICP） and South China Sea （SCS） are analyzed, along with the effects of such a thermal contrast on the SCS monsoon onset （SCSMO）. It is shown that there exists significant seasonal evolution for such a thermal contrast. The surface temperature of ICP is higher than that of SCS during the 3rd 25th pentad due to the effects of the sensible heating in ICP. After the 25th pentad, such a thermal gradient will reverse, in response to the decrease of the surface temperature of ICP, which is resulted from the convection and rainfall there in the 22- 23th pentad. Furthermore, the above seasonal evolution of the discussed thermal contrast also demonstrates a remarkable interannual change, which plays an important role in the SCSMO. The reversion of the thermal contrast happens prior to （or simultaneously with） the SCSMO each year during 1958 - 1998, thus becoming a precondition for the SCSMO. The earlier （later） the date on which the surface temperature of ICP becomes higher （lower） than that of SCS, the later the SCSMO.