基于OFES模式数据的北赤道流分叉研究

ANALYSIS ON THE NORTH EQUATORIAL CURRENT BIFURCATION USING OFES OCEAN MODEL DATA

利用1957—2006共50年高分辨率的长时间序列海洋模式OFES(OGCM for the Earth Simulator)数据,对北赤道流(NEC)的分叉规律及其与ENSO循环的关系进行了分析。结果表明:(1)NEC分叉纬度具有明显的季节和年际变化,周期主要呈现为3—6个月的季节内振荡和2年、2—7年左右ENSO尺度周期振荡以及10年以上的年代际变化。在季节尺度上,分叉位置春季偏南,秋季偏北,并且分叉纬度随深度的增加向北移动,其北移幅度冬季最大,夏季最小。而在年际变化尺度上,NEC分叉纬度具有较强的年际变化信号,与ENSO循环密切相关,El Ni?o年分叉位置偏北,La Ni?a年分叉位置偏南。(2)NEC分叉纬度的变化与北太平洋0—30°N之间的纬向风应力旋度积分零线位置密切相关,零线的南北偏移导致了分叉位置的改变,在不同深度上,零线位置对分叉纬度改变的影响时间不同,表层需1个月,而500 m深度则需4个月左右。(3)NEC分叉影响着黑潮(KC)与(棉兰老流)MC的流量分配率,其年际异常变化与冷、暖ENSO事件发生密切相关,当El Ni?o发生时,KC流量分配率减少,MC流量分配率增加;La Ni?a年情况则相反。

Spatial and temporal characteristics of North Equatorial Current （NEC） and its relationship with ENSO cycles were analyzed using a 50-yearoutput from a high eddy-resolving numerical model OFES （OGCM for Earth Simulator）. Results show that： （1）TheNECbifurcationlatitude（NBL）variesseasonally in 3—6-month period, interannually in 2a or 2—7a period, and interdecadally in 〉10-year period. Seasonally, NBL moves southward in spring and northward in autumn, also moves northward as the depth increases. Interannually, changes in NBL are closely related withENSOcycle.Thebifurcation latitude moves northward in El Nino event, while moves southward in La Nina event. （2） NBL can be determined at the zero line of zonalwindstress curl between 0—30°N in the North Pacific, and the temporal point varies with depth for about one month at surface that increases gradually to four months at bottom. （3） The distributions of Kuroshio （KC） and Mindanao Current （MC） are affected by NBL and correlated with the ENSO cycle. During El Nino period, the distribution of KC transport volume from the Equatorial Current is smaller than that of the MC, and vice versa during La Nina.