碩士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 93 / Abstract
Satellite-sensed Advanced Very High Resolution Radiometer (AVHRR) sea surface temperature (SST) data over eight winters (1996-2003) and shipboard measurement during winter 2002 were used to analyze the winter SST patterns of variability in the middle of Taiwan Strait. These satellite-derived SST images conducted by MCSST and NLSST algorithm in the waters around Taiwan were firstly validated from a match-up data set of 961 pairs, which included the in situ SSTs and concurrent AVHRR measurements for the period of 1998 to 2002. Availability of cloud-free images, which had more than 85% of cloud-free area in their coverage, was about 2.23 % of the whole AVHRR senses in the study period. The range of in situ SSTs was from 10.5℃ to 30.8 ℃. The satellite derived-SSTs through the MCSST and NLSST algorithms with the NOAA-published coefficients are linearly related to the in situ SSTs with correlation coefficients of 0.985 and 0.98, respectively. The MCSSTs and NLSSTs have small biases of 0.01 ℃ and 0.26 ℃ with the root mean square deviation 0.64 ℃ and 0.80 ℃, respectively, which conclude that the AVHRR-based MCSSTs and NLSSTs have high accuracy in the waters around Taiwan.
Empirical orthogonal function (EOF) analysis of the spatial and temporal variance for 81 nearly cloud-free quarter monthly images was performed. The time series of spatial mean SST was like a non-linear mode associated with the seasonal thermal variation, having an average value about 20 ℃. The EOF analysis shows that the variance of oceanic feature was more significant in space than in time. The first mode (85.7%) of the spatial variance shows a persistent front near the Chang-Yuen Ridge in the middle of Taiwan Strait, which separates warmer surface water (>22 ℃) to the southeast from the colder waters (<19 ℃) off Mainland China to the northwest. The maximum temperature and salinity gradient at Chang-Yuen Ridge were found about 0.11℃/km and 0.048 psu/km, respectively. The second and third spatial variance modes are extremely low energy about 3.13% and 1.92 %, respectively.
The EOF’s signal and field observation revealed that the heating exchange, balance and its strength (i.e. coolness index) of cold water to warm water were temporally shifted in winter. From these images, we also constructed an overall coolness index, which revealed the relative strength of Mainland China Coastal Current in relation to the interaction of the South China Sea Warm Current and Kuroshio Counter Current.
In other words, the higher the coolness index is, the larger the coverage area of KBC northward intruding into Taiwan Strait. Among them, this regression line with the higher coefficient 0.71 was only reach to the significant level 95% at the temperature range larger than 20 ℃. It also suggested that the isotherm line of sea surface temperature 20 ℃ might be served as a winter thermal front boundary index of MCCC and KBC in Taiwan Strait.
Keyword: Sea surface temperature (SST), Validation, EOF, AVHRR, Taiwan Strait, Coolness index, Kuroshio Counter Current.
| Identifer | oai:union.ndltd.org:TW/093NTOU5451012 |
| Date | January 2005 |
| Creators | Yi Chang, 張懿 |
| Contributors | Ming-An Lee, 李明安 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 75 |
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