采用POMgcs(Princeton Ocean Model with generalized coordinate system)和MITgcm(MIT General Circulation Model)两个海洋数值模式,研究了M-Y2.0、基于固壁近似假定的M-Y2.5、基于波浪破碎作用的M-Y2.5和KPP 4种垂向混合参数化方案对模拟黄海夏季上层温度结构的影响。结果表明,M-Y2.0和基于固壁近似假定的M-Y2.5方案低估了黄海上层的湍动能,模拟的黄海夏季温度上混合层的效果与实测相比均偏浅,不能够很好地重构黄海夏季温度的垂直结构。而基于波浪破碎作用的M-Y2.5和KPP方案均可以增加海洋上层湍动能的输入量,模拟的黄海夏季温度上混合层的效果与实测较为一致。故推测黄海夏季的上层结构是受波浪混合和流场剪切等物理机制共同调节的,若通过合理的垂向混合参数化方案将这些物理机制的作用加以体现,将会较真实地模拟和重构出黄海夏季海温上层结构。
By using the reanalysis data, the impact of oceanic eddies and frontal wave on Kuroshio front to the east of Taiwan （KFETW） is studied. The result indicates that cold eddies （warm eddies） corresponding to the first baroclinic mode of Rossby wave can weaken （strengthen） the strength of the KFETW and narrow （widen） the width of this front. A frontal wave of the KFETW during January to February in 1991 is detected from the reanalysis data. And the trough （crest） of the frontal wave may weaken （strengthen） the strength of the KFETW and narrow （widen） the width and thickness of this front. It is found through the diagnostic analysis of the energy source of the frontal wave that the contribution of barotropic instability or that of baroclinic instability is more than that of Ketvin-Helmholtz （K-H） instability by 1 - 2 order of magnitude, and the contribution of the baroclinic instability is 5 times than that of the barotropic instability, thereby the frontal wave is basically driven by the baroclinic instability.
Oceanic front, especially Kuroshio front, is an important phenomenon that is of great significance for scientific research, national economy and military uses. However, Kuroshio front to the east of Taiwan （KFETW in brief） was rare investigated. In this study, reanalysis method is used to study the KFETW＇s temporal and spatial variability and frontogenesis mechanism. It is found that although surface thermal front to the east of Taiwan is not obvious, there is an all-year strong Kuroshio thermal front called KFETW under the surface. The KFETW is connected to the south section of Kuroshio front in the East China Sea （KFECS in brief） and distributes along the east coastline of Taiwan. The KFETW has multi-scale variation feature. It has significant seasonal signal, and its intensity and width reach their maximum in summer. By using the reanalysis results obtained from this study, frontogenesis and changing mechanisms of the KFETW are discussed. It is found that both the Kuroshio and up-welling to the east of Taiwan can affect this front, and the up-welling may be the predominant factor in KFETW＇s frontogenesis and maintenance mechanism.
首先利用考虑波浪破碎效应的Mellor-Yamada 2.5阶湍流闭合方案,探讨了海表温度(SST)对波能因子α和Charnock数β的敏感性问题。然后采用变分数据同化途径,基于Papa海洋天气站(OWS Papa Station)的上层温度观测数据,对该参数化方案中的波能因子α和Charnock数β两个参数进行了最优估计。最优估计的结果表明,当α约为167、β约为4.1×105时,价值函数达到最小值。利用上述参数的最优估计进行海温的数值模拟,可以较好地反映出海表温度的日变化和月变化过程,模拟的上混合层的温度和深度也与观测较为一致。最后利用以上参数的最优估计结果对湍动能方程进行诊断计算,研究了波浪破碎对海洋上层湍能量收支的影响。
