Title page for etd-0529117-154113


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URN etd-0529117-154113
Author Yu-Ting Chang
Author's Email Address No Public.
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Department Department of Oceanography
Year 2016
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title On the linkage of internal soliton and surface roughness
Date of Defense 2017-06-28
Page Count 59
Keyword
  • EMD method
  • pressure signals
  • EEMD method
  • surface roughness
  • internal wave
  • Abstract According to the previous studies, the convergent and divergent zones of an internal soliton wave train can be distinguished from the roughness of sea surface observed by the radar remote sensor. Similar results were also described in the SAR images. Historical studies showed that a convergent zone was related to the arrival of a depression internal soliton. In the meantime, the rough sea surface was shown which presented white zones in SAR image. The following was a divergent zone with smooth sea surface which was a dark zone shown in SAR image. Comparing with these studies, however, the timing of those phenomena did not match well when internal soliton waves were observed during the field works. As a result, the main purpose of this research is to determing if the roughness phenomenon on sea surface is consistent with the wave forms measured under the sea surface.
    A mooring of thermistor string with several pressure sensors was deployed at east slope of Dongsha Atoll region during 2015/10/1 to 2015/10/2. A high-resolution pressure meter was located at the depth of 10 meters to detect the surface roughness. Several CTD casts were during the arrival of internal solitons. The mooring recorded two groups of internal waves successfully. Photos and videos were also applied to record the rough and smooth phenomena on the sea surface.
    Internal solitons were selected based on the record of the moored thermistor string. The EMD and EEMD were applied to the data from the high-resolution pressure meter . The amplitudes and periods of solitons were therefore identified. The results show that the depression internal soliton can produce swells at convergent zone, then followed by ripples. However, the position of smooth phenomenon couldn’t be determined based on this experiment.
    The EEMD method can separate the noise with period less than 2-second from the other signals. The signals extracted from EEMD (noise_IMF3) were similar to the surface swells caused by internal soliton of depression waves form before the arrival of convergent zone. The period of these swells are about 6 to 9 seconds. In addition, the rough phenomena (noise_IMF2) with period of 2 to 5 seconds and smaller wave heights probably can be related to the ripples. Also, the extracted EEMD signals (noise_IMF4) can be related to wind with the period is about 11 to 14 seconds.
    No matter how the wave form of internal wave is, we found the results from EMD and EEMD are simillar. The analysis concludes that the sea surface roughness is produced and transfer forward when the internal soliton formed.
    Advisory Committee
  • Chung-Pan Lee - chair
  • I-Huan Lee - co-chair
  • Yih Yang - co-chair
  • Yu-Huai Wang - advisor
  • Files
  • etd-0529117-154113.pdf
  • Indicate in-campus at 1 year and off-campus access at 1 year.
    Date of Submission 2017-06-29

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