【作者】 李强；

【导师】 吴德星；

【作者基本信息】 中国海洋大学 ， 物理海洋学， 2004， 硕士

【摘要】 太平洋除了存在类似ENSO的年际变化以外，还存在年代际尺度的变化，其在北太平洋主要表现为PDO(太平洋年代际涛动)现象，并且太平洋在1976-1977年附近存在气候的跃迁。有关太平洋年代际变化机制的研究，尚存在诸多的争议。 本文利用现有的JEDAC、NCEP、COADS等资料，分析了PDO现象的时间与空间变化特征，并讨论了大气风场对PDO现象的贡献，风应力的变化对PDO为一正反馈作用。 根据PDO现象的上述特征，建立了一非线性海气耦合模型以解释太平洋年代际变化的形成和发展机制。这一模型的定性分析结果表明，中纬度纬向风异常引起的Sverdrup输运对该地区热量年代际尺度上的收支起重要作用；高纬和低纬的温度差是维持中纬度异常风场的重要因素。当该温差达到某一临界值时，由于海气耦合系统的非线性作用，会产生异常风场的突变。风场的异常变化又会重新改变高纬和低纬的热收支，从而产生不连续的耦合的振荡，这一振荡的周期是年代际尺度。因此，中纬度太平洋自身也可以产生年代际的振荡。并且这一海气耦合机制同样适用于大西洋。另外，这也同时表明10°N-20°N上层热含量的年代际变化并不完全是由潜沉作用引起的。 热带太平洋与中纬度存在相似的年代际变化，也存在类似PDO准20年和20年以上周期的异常信号，NINO3指数和PDO指数存在良好的正相关，并且热带太平洋东、西海区分别与黑潮延伸体处的上层热含量异常成正相关和负相关。 根据中纬度海气耦合系统的分析，太平洋低纬度上层热含量也存在年代际的变化，并且与高纬度存在负相关。这一区域热含量的异常会影响赤道区的东风，从而产生在热带太平洋东西部的热含量异常的年代际反位相振荡。ENSO等短时间尺度现象的调制作用对赤道海区东西反位相振荡的贡献不可忽视。因此热带太平洋准20年及20年以上年代际变化的源地可能是在中纬度。另外，热带太平洋上层热含量和温跃层还存在准10年际的西行信号。更多还原

【Abstract】 Observations and air-sea models indicate that decadal to interdecadal variabilities exist in the Pacific Ocean. In the North Pacific, the decadal variability is expressed as PDO (Pacific Decadal Oscillation). In 1976-1977, there is a climate "Regime Shift" in the Pacific Ocean. So tar oceanographers and meteorologists have not come to agreement about the physical mechanism of this decadal fluctuation.This paper has analyzed the temporal and spatial patterns of PDO on the basis of some variable data from JED AC, NCEP/NCAR and COADS, and also discussed the effect of zonal wind to PDO, coming to the conclusion that the local wind stress in the North Pacific is a positive feedback to the PDO.Based on the above analysis, a nonlinear air-sea coupled model is constructed to analyze the formation and development mechanism of the decadal variability in the Pacific Ocean. There are indications that, in the midlatitude, the Sverdrup transport resulted from the zonal wind anomaly plays an important role to the heat budget in the high and low latitude. The difference in temperature between high and low latitude is a key factor to sustain this zonal wind anomaly in the midlatitude. When this difference is great to some extent, owing to the non-linearity in the air-sea coupled system, the zonal wind in midlatitude will jump from one state to another, which in turn effects the heat storage in the high and low latitude. Thus there will be a discontinuous oscillation in this coupled system. Therefore, decadal oscillation can also be formed by itself in the midlatitude of the Pacific Ocean. This formation mechanism isalso available in the Atlantic Ocean. Besides, the above analysis suggests that the upper layer heat storage variability in 10?N-20?N is not entirely resulted from the subduction water originated in the north.The decadal variability in the tropical Pacific shares some common characteristics with the North Pacific. There also exist anomalous signals similar to the PDO period of more than 20 years. There is a good positive correlation between NINO3 index and PDO index. The east and the west tropical Pacific Ocean are positively and negatively correlated to the anomaly of the upper layer heat storage in the Kuroshio and Oyashio Extension, respectively. Air-sea model and data analysis also show that a decadal variability of the upper layer storage exists in the low latitude, which is negatively correlated to that in the high latitude. The anomaly of the upper layer heat storage in the low latitude may affect the equatorial easterly wind and results in the decadal anti-phase oscillation of the upper layer heat storage in the tropical Pacific Ocean. The negative correlation of the anomaly of the heat storage in the eastern Pacific may also probably come from the modulation of ENSO. So the origination of this oscillation in the tropical Pacific may be in the midlatitude. In addition, the upper heat storage and the thermocline in the tropical Pacific also contain the westward signals of 10-year period.更多还原