Correlation analysis of the North Equatorial Current bifurcation and the Indonesian Throughflow
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摘要: 利用1958-2007年的SODA月平均资料,对北太平洋西边界流(NKM)、北赤道流分岔点位置(NBL)和印尼贯穿流(ITF)的季节、年际变化进行分析。在此基础上,对NBL、ITF流量、NEC流量及Niño3.4区指数的年际变化做经验模态分解(EMD),并设计实验对本征模函数(IMFs)做超前滞后相关分析。季节变化的分析结果显示:NBL春夏南移,秋冬北移,年平均在14.33 °N左右;ITF流量北半球夏季大、冬季小,其年平均流量为7.75×106 m3/s。年际变化的分析结果显示:北赤道流流场的变迁是ENSO事件的一个前兆,NBL的南北震荡将在2个月后对Niño3.4区指数有响应,且二者呈正相关,最大相关系数为0.53。NBL北移,ITF流量减小,NBL超前ITF流量变化7个月时,二者正相关最大,相关系数为0.43。在El Niño年,NEC和黑潮(KC)流量减小,棉兰老流(MC)流量增加,ITF流量减小,ITF流量变化滞后Niño3.4指数变化3个月。La Niña年则相反。Abstract: Based on monthly mean Simple Ocean Data Assimilation (SODA) products from 1958 to 2007, this study analyzes the seasonal and interannual variability of the North Equatorial Current (NEC) bifurcation latitude and the Indonesian Throughflow (ITF) volume transport. Further, Empirical Mode Decomposition (EMD) method and lag-correlation analysis are employed to reveal the relationships between the NEC bifurcation location, NEC and ITF volume transport and ENSO events. The analysis results of the seasonal variability show that the annual mean location of NEC bifurcation in upper layer occurs at 14.33°N and ITF volume transport has a maximum value in summer, a minimum value in winter and an annual mean transport of 7.75×106 m3/s. The interannual variability analysis indicates that the variability of NEC bifurcation location can be treated as a precursor of El Niño. The correlation coefficient between the two reaches the maximum of 0.53 with a time lag of 2 months. The ITF volume transport is positively related with El Niño events with a maximum coefficient of 0.60 by 3 months. The NEC bifurcation location is positively correlated with the ITF volume transport with a correlation coefficient of 0.43.
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