中等复杂程度全球热带海洋模式模拟的热带印度洋海表温度变率

SST Variability in the Tropical Indian Ocean Simulated by an Intermediate Tropical Global Ocean Model

利用一个中等复杂程度全球热带海洋模式模拟研究了表面强迫异常引起的热带印度洋海表温度(SST)变率.利用1958-1998年表面分析资料作为强迫场,积分海洋模式41年作为控制试验,并利用模式分别做动量(风应力)通量和热量通量无异常变化的平行试验,与控制试验作比较.通过3组试验模拟的上层海洋变率状况的比较,分析了动量和热量通量异常对热带印度洋SST变率的影响,并比较了其影响的相对重要性.结果表明,模拟的热带印度洋SST变率的主要模态表现为与热带太平洋ENSO相联系的海盆尺度的一致性增暖或变冷特征,次级模态为热带印度洋SST偶极子模态.通过3组试验结果的比较表明,动量通量和热量通量异常强迫对热带印度洋SST变率第一模态均有贡献,但热量通量异常强迫的影响比动量通量异常强迫的作用大.热带印度洋偶极子模态主要受动量(风应力)异常强迫影响,热量通量异常强迫主要起阻尼作用.

This study presents a simulation of the sea surface temperature variability in the tropical Indian Ocean and an investigation of relative contributions of the surface wind stress forcing and the heat flux forcing to the upper ocean variability, with an intermediate ocean model (IOM) developed in Hawaii University. The model was integrated for the 1958-1998 period (41 years) as a control experiment, forced with both anomalous wind stresses and heat fluxes. Two parallel sensitive experiments were conducted, which was the same as the control run without the wind stress anomalies and the surface heat flux anomalies, respectively. The relative importance of the two forcing factors in generating the upper ocean variabilities of the sea surface temperature (SST) and the thermocline depth was examined. The model successfully simulates not only the El NinoSouthern Oscillation related basinwide warming/cooling mode, but also the dipole mode of the tropical Indian Ocean as well as that of the nearsubtropical Indian Ocean. In the Indian Ocean, the anomalous heat flux plays a more important role in the first EOF mode of SST variations on the interannual timescale than the anomalous wind stress. The wind stress anomaly favors a positive feedback mechanism for the dipole mode of the tropical Indian Ocean while the heat flux anomaly plays a damping role. 