Two Types of Interannual Variability of South China Sea Summer Monsoon Onset Related to the SST Anomalies before and after 1993/94
Two Types of Interannual Variability of South China Sea Summer Monsoon Onset Related to the SST Anomalies before and after 1993/94
复制标题
1993/94年前后与海温异常相关的南海夏季风爆发的两种年际变化
DOI：
10.1175/jcli-d-16-0065.1
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发表时间：
2016
影响因子：
4.9
通讯作者：
Xu Kang
中科院分区：
文献类型：
--
作者：
Liu Boqi;Zhu Congwen;Yuan Yuan;Xu Kang
1980-2014年南海夏季风（SCSSM）发生时间的提前可以在1993/94年之后发现。基于对流层上下环流垂直耦合的不同特征及其相关海温异常（ssta）的差异，本文将1993/94年前后南海ssm爆发的年际变率划分为两类。在年际尺度上，1980—1993年，ⅰ型SCSSM的发生与南海北部低层环流异常有关，而1994—2014年，ⅱ型SCSSM的发生与热带高层环流异常有关。对流层上层热力场和南海上空环流结构在两种类型的ssm爆发中具有明显的差异，表明南印度洋春季ssta （SIO）和ENSO事件分别在i型和ii型ssm爆发中发挥了重要作用。在早期事件中，变暖的SIO ssta可以在南海北部诱发一个异常的低层反气旋，影响其北部陆地上的局地季风对流和降雨，表明副热带系统对i型SCSSM的爆发具有高度敏感性。然而，在后期的ii型SCSSM中，冬季温暖的ENSO事件和随后的热带印度洋变暖可以通过调节春季热带温度和南海上层泵送效应来影响SCSSM的发生。
An advance in the timing of the onset of the South China Sea (SCS) summer monsoon (SCSSM) during the period 1980–2014 can be detected after 1993/94. In the present study, the interannual variability of the SCSSM onset is classified into two types for the periods before and after 1993/94, based on their different characteristics of vertical coupling between the upper- and lower-tropospheric circulation and the differences in their related sea surface temperature anomalies (SSTAs). On the interannual time scale, type-I SCSSM onset is characterized by anomalous low-level circulation over the northern SCS during 1980–93, whereas type-II SCSSM onset is associated with anomalies of upper-level circulation in the tropics during 1994–2014. The upper-tropospheric thermodynamic field and circulation structures over the SCS are distinct between the two types of SCSSM onset, and this investigation shows the importance of the role played by the spring SSTAs in the southern Indian Ocean (SIO) and that of ENSO events in type-I and type-II SCSSM onset, respectively. In the early episode, the warming SIO SSTAs can induce an anomalous low-level anticyclone over the northern SCS that affects local monsoonal convection and rainfall over land to its north, demonstrating a high sensitivity of subtropical systems in type-I SCSSM onset. However, in type-II SCSSM onset during the later episode, the winter warm ENSO events and subsequent warming in the tropical Indian Ocean can influence the SCSSM onset by modulating the spring tropical temperature and upper-level pumping effect over the SCS.