碩士 / 國立臺灣大學 / 海洋研究所 / 100 / The observative data from moorings deployed in the east of the Luzon Strait show that internal tides are active in the Northwestern Pacific. Spectral analysis of the temperature data of upper 500m shows that diurnal tides and semidiurnal tides are the two primary kinds of tides. In contrast to semidiurnal tides, diurnal tides are dominant. The rotary spectral analysis of the velocity data shows that both of them are propagating in the East-West direction, and it means that internal tides generated from the Luzon Strait.
There are different patterms about temperature variations which induced by diurnal internal tides. In most of the observational time, there are obvious time lags about the variations of temperature between different depths, while in some observational time, there is no time lag about the temperature varibations between different depths. The former means that internal tidal beams propagate in the vertical direction so the propagating mode is dominant, and the latter means that the internal tidal beams do not propagate in the vertical direction so the standing mode is dominant. There are some obvious relationships between the stratification and temperature variations which induced by diurnal internal tides. When there are obvious time lags about the temperature varibations between different depths and the propagating mode is dominant, there is no peak value about buoyancy frequency in a narrow vertical range, on the contrary, when there is no obvious time lag about the variations of temperature between different depths and the standing mode is dominant, there is a peak value about buoyancy frequency in a narrow vertical range. According to the theoretical interpretations and the model simulations, the different patterns about the variations of temperature which induced by diurnal internal tides are caused by the propagating internal tidal beams which was affected by the stratifications of the ocean and the simulations from the iTide model explains the internal tidal beam structure in the vertical direction.
There are some high-frequency internal solitary waves can be observed from the data. The high-frequency internal solitary waves occur during the time when bouyance frequency has a peak value in a narrow vertical depth range. It means that the high-frequcncy internal solitary waves appear if the stratification is stronger. The satellite data illustrates that the stronger stratification may be caused by the cyclonic cold eddies near the moorings. The model simulations, Theo Gerkema [2001] show that internal solitary waves only appear when the thermocline is moderated developed. Under the moderated developed thermocline, the high-frequency internal waves will emerge from the interface. As above, the cyclonic cold eddies may make the stratification to be stronger and provide the ‘better’ stratification for generating high-frequency internal solitary waves.
| Identifer | oai:union.ndltd.org:TW/100NTU05279025 |
| Date | January 2012 |
| Creators | Cheng-Da Tsai, 蔡承達 |
| Contributors | Tswen-Yung Tang, 唐存勇 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 66 |
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