臺灣博碩士論文加值系統

根據諸多文獻記載，當海洋有內孤立波通過時，該海域海表面粗糙度可能有明顯的變化。當下沉型內孤立波通過時，會先有一輻合帶，對應海表面的高粗糙值，在SAR衛星影像上呈現亮白色，隨後有一輻散帶，海表面為平滑現象，並在SAR衛星影像上呈現暗色。這些理論的敘述與現場觀測的內波在時間上卻並非十分準確。因此本研究想探討海面所觀察到的粗糙現象，與海面下的實測內孤立波波型是否吻合。
現場實驗於2015年10月1日至2日，在東沙海域東邊斜坡處施放一組錨碇溫度計串，水下10米安裝一個高解析度壓力計，並在內孤立波經過時間施放溫鹽壓探測儀(CTD)做檢驗。實驗成功紀錄到兩群內孤立波，海表面觀察到粗糙和平滑的現象，以影像及影片作紀錄，並以溫度計串及壓力資料選取內孤立波經過時間。壓力變化資料可經EMD及EEMD方法分析出各個內孤立波所造成海面粗糙現象的振幅及週期。結果顯示下沉型內孤立波會先在輻合帶上產生湧浪接著漣波，但平滑現象的位置目前還無法以此實驗得到結果。而經EEMD分解，可將週期小於2秒的雜訊(noise_IMF1)和其他訊號分離，在輻合帶前有類似內波造成的湧浪(noise_IMF3)，週期約在6至9秒間，另外有週期約在2至5秒間且波高較小的粗糙現象(noise_IMF2)，可能是儀器的雜訊或是漣波現象，亦有類似於海面上因風造成的湧浪(noise_IMF4)，週期約在11至14秒。不論內波波型為何皆有發現，因此推論海表粗糙度是在內孤立波形成時便已產生並向前傳遞。

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.

論文審定書 i
致謝 ii
摘要 iii
Abstract iv
圖目錄 viii
表目錄 xi
第一章、緒論 1
1.1前言 1
1.2前人研究 2
1.3研究目的 7
第二章、現場觀測與資料蒐集 10
2.1研究區域 10
2.2現場觀測 10
2.3資料收集 14
第三章、資料處理與分析方法 16
3.1 資料品管與展示 16
3.1.1壓力資料 16
3.1.2溫度資料 17
3.1.3海流資料 19
3.2 壓力資料分析方法 21
3.2.1 帶通濾波(Band Pass) 24
3.2.2 FFT 24
3.2.3 EMD及EEMD 25
3.2.4 波浪之零上切法 30
第四章、結果與討論 32
4.1海面變化與海面下內波的位置 32
4.2了解海面訊號與內波的關係 33
4.3觀察海面訊號是否會因內波的形變而產生變化 34
4.4探討海面訊號形成的時機 35
4.5理論壓力值的計算 37
第五章、結論 43
5.1 結論 43
5.2 未來工作 43
參考文獻 44
附錄 46

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