L.-C. WU ET AL. 65
regional sea areas around Taiwan, through the analysis of
in-situ tide gauge and satellite altimetry records. After
calculating the sea level tren ds from the altimetry record s,
we revealed similarities in the rates associated with sea
level trends calculated in the same sea area. However,
differences in the trends of sea level change calculated in
different sea areas around Taiwan can be as high as 5
mm/year.
In addition, sea surface heights around Taiwan are
higher than the global mean surface height. It should also
be noted that the calculated results between in-situ and
altimeter records were quite different in some sea areas
around Taiwan. Subsidence and land surface uplift no
doubt have a significant influence on the accuracy of
calculated sea level trends. We also discussed the prob-
ability distribution of sea level records. The results of
distribution fitness showed spatial inhomogeneity of sea
level records, and differences in the distribution from
altimeter time series within the same matrix, particularly
in the west sea area of Taiwan.
To reveal the fluctuations in sea level records, we em-
ployed various tools incorporating spectral transform.
From the results of Fourier spectra, we confirmed a num-
ber of obvious fluctuations in the sea level records. An-
nual fluctuations in most of the sea level records from
altimeter and in-situ tide gauge records were quite obvi-
ous, and a few of the astronomical tide con stituents were
observed in the Fourier spectra. In addition to the Fo urier
spectra, we discussed the non-stationary features of sea
level time series according to wavelet scalograms. The
energy density from various frequency bands showed
non-stationarity in the time series of altimeter records.
The non-stationarity indices calculated from the wavelet
scalograms showed that the sea level oscillations were
more non-stationary in the sea area of eastern Taiwan
than they were in other sea areas around Taiwan.
5. Acknowledgements
This work was supported by the Water Resources
Agency (MOEAW RA0990248) and the Nation al Science
Council (NSC 98-2923-I-006-001-MY4 and NSC 100-
2221-E-006-020) in Taiwan. The authors would like to
offer their sincere thanks to the agencies.
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