北太平洋环流振荡形成机理的数值研究

Numerical Study on the Formation Mechanism of the North Pacific Gyre Oscillation

利用大洋环流模式,探讨海洋对大气强迫的响应及北太平洋环流振荡模态(NPGO)形成的直接原因。对控制试验模拟的海表温度异常(SSTA)进行经验正交函数(EOF)分解,发现第二模态类似于经典NPGO模态,说明采用该模式研究海洋对大气强迫的响应是可行的。在控制试验基础上,通过改变大气强迫场设计了一系列敏感试验,发现大气强迫场为NPGO模态正强年的合成场时,所得SST异常场能较好再现NPGO空间特征,说明海洋状态强烈依赖于大气强迫,大气强迫是造成NPGO的直接原因;对大气强迫场中的动力强迫、热力强迫等物理量进行不同配置进行试验,发现风场动力强迫对NPGO的影响最大,是形成NPGO的关键强迫,其中又以纬向风应力的影响居首。

An oceanic general circulation model is adopted to study the oceanic response to atmospheric forcing and the formation mechanism of the North Pacific Gyre Oscillation(NPGO).The control experiment shows that the numerical model can successfully simulate the spatio-temporal features of the NPGO,suggesting that the model can be used to study the formation mechanism of the NPGO.The SST anomaly fields simulated by the model being forced with composed atmospheric fields of positive strong NPGO years are similar to the spatial pattern of the NPGO mode,suggesting that the atmospheric forcing is the direct mechanism of NPGO fromation.Sensitivity experiments reveal that the dynamic effect of wind is most important to the formation of NPGO,especially the effect of zonal wind stresses.