The Intraseasonal Long Rossby Wave In The Subtropical Ocean And Its Effect To The Kuroshio In The East China Sea

The satellite altimeter data reveal that intraseasonal long Rossby wave is the most obvious wave signal in the subtropical ocean. Because it has a great effect on the variation of energy, momentum, and heat flux as well as the interaction of large and middle scale processes, and it also affects the Kuroshio in many ways, the study on the intraseasonal long Rossby wave is important and practical. Based on the data analysis, theoritic studies and numerical simulation, this paper will focus on the amplification mechanism, the character of wave speed and the effects to the Kuroshio of the intraseasonal long Rossby wave.Based on a two and half layer ocean model the long Rossby wave dispersion relation and the corresponding baroclinic instability criterion are derived. It can infer that the intraseasonal long Rossby wave may be amplified by the baroclinic instability. According to the baroclinic instability criterion the paper gives the baroclinic instability area of North Subtropical Pacific Ocean from the Levitus 98 climatic data. The baroclinic instability area is well in accord with the amplification area of the intraseasonal long Rossby wave, and this proves that the baroclinic instability is the main amplification mechanism of the intraseasonal long Rossby wave. The consistency between the baroclinic instability area and the potential vorticity (PV) pool is further proved in this paper, from which one could conjecture that the intraseasonal long Rossby wave is amplified in the PV pool. The changeable of PV pool with time leads to the variation of wave amplification area. Because the relatively large ocean basin and weak ventilation, the PV poolThe Intraseasonal Long Rossby Wave in the Subtropical Ocean and its Effect to the Kuroshio inthe East China Seais much larger in the North Pacific Ocean than in the North Atlantic Ocean. This is the reason why the wave amplification areas are much different in these two oceans.The analysis of the satellite altimeter data suggests that the propagating speed of intraseasonal long Rossby wave amplified in the subtropical Pacific ocean is faster than that of first-mode baroclinic free Rossby wave predicted by the liner theory and the propagating speed of intraseasonal long Rossby wave reflected in the eastern boundary of Pacific Ocean agrees basically with the liner theory speed of first-mode baroclinic free Rossby wave. According to the critical frequency theory this paper gives the period of intraseasonal long Rossby wave reflected in the eastern boundary of Pacific Ocean. The period of intraseasonal long Rossby wave reflected in the eastern boundary is longer than the period of intraseasonal long Rossby wave amplified in the subtropical ocean, and this also proves the speed differences of these two Rossby waves. The acceleration of the propagating speed of intraseasonal long Rossby wave amplified in the subtropical Pacific Ocean is due to the existence of westward thermolcline mean flow in the PV pool.The analysis of sea level data from tide stations and ocean general circulation model (OGCM) as well as the float data and section data shows that the intraseasonal long Rossby wave results in the intraseasonal variations of Kuroshio axis and transport in the upper reaches of the Kuroshio in the East China Sea (ECS). Due to the transport modulation induced by Ryukyu Islands, the intraseasonal variation is very weak in the lower reaches of the Kuroshio in the ECS. A two-layer model reveals the relation among Kuroshio unstable wave with topography, transport and the axis position of the Kuroshio, from which we can infer that the intrusion of intraseasonal long Rossby wave may stimulate the Kuroshio unstable wave in the upper reaches of the Kuroshio in the ECS. TheThe Intraseasonal Long Rossby Wave in the Subtropical Ocean and its Effect to the Kuroshio inthe East China Seaaltimeter data also shows that the sea level anomaly resulting from intraseasonal long Rossby wave could pass the channel between Taiwan and Ryukyu Islands and propagate northeastward in accord...