春季Wyrtki急流异常及其与亚洲热带夏季风的关系

采用热带印度洋上层洋流的复EOF分解,对春季Wyrtki急流异常及其年际、年代际变化做了研究,并探讨了其与南海、南亚夏季风的关系。结果表明:该分解第一模态可称之为Wyrtki急流模态,其反映了每年5月份Wyrtki急流的总体强度;该强度有非常明显的8 a年际变化,这与亚洲夏季风年际变化之一相近;还有17 a和23 a的年代际变化,其中后者与热带外北太平洋主要气候模态PDO的周期相近。Wyrtki急流强度偏弱(强)年,南海、南亚夏季风建立大多偏早(迟),南海夏季风大多偏强(弱)。第二模态反映了Wyrtki急流在整个赤道印度洋东、西方向的不均匀性;其有非常明显的11 a和18~19 a的年代际变化,其中前者与热带外北太平洋次要气候模态NPGO的周期相近;此外该模态还有5 a的年际变化。

Wyrtki Jet anomaly in May and its relationship with Asian tropical summer monsoon

The Complex EOF (CEOF) analysis of the upper abnormal circulation of the tropical Indian Ocean in May was carried out based on 52 years Carton data. The inter-annual and inter-decadal variation of Wyrtki Jet, and the relationship between the Jet and the Asian tropical summer monsoon were presented. The main results show that the first mode could be called as Wyrtki Jet mode which reflected the general intensity of Wyrtki Jet in May of every year. The first mode had obvious inter-annual variation in every 8 years, which was consistent with one of the inter-annual variations of Asian summer monsoon. It also had obvious inter-decadal variations in every 17 and 23 years. The latter was consistent with the PDO period of the main climate mode in North Pacific. When the intensity of Wyrtki Jet was weaker, the estabishment data of the summer monsoon in South China Sea and South Asia was usually earlier, and the summer monsoon in South China Sea was most likely stronger, and vice versa. The second mode reflected the non-uniformity of Wyrtki Jet in the east and west directions of equatorial Indian Ocean. It had very obvious inter-decadal variations in every 11 and 18-19 years. The former was consistent with the period of NPGO of the secondary climate mode in North Pacific. The second mode also had inter-annual variation in every 5 years.