Pathways of the surface current off southwest Taiwan in winter : Observations from HF Radar
Date Issued
2015
Date
2015
Author(s)
Wang, Wei
Abstract
Variations of the surface currents in the sea Southwest of Taiwan (SWT) were investigated by High Frequency Radar (HF Radar), which had measured surface currents from Nov. 2013 to Feb. 2014. Several short-term changes in surface currents have been found. One notable change is that the rotating currents have produced with a period for about ten days between the Anping-Kaohsiung and Penghu Islands. For example, the cyclonic rotation currents were found in Nov. 2013 whereas the anti-cyclonic rotation currents were found in Jan. 2014 to Feb. 2014. Using Real-vector empirical orthogonal function (REOF) to analyze surface currents in the SWT has revealed that almost 74 % of total variances of currents in first three modes. A large clockwise current structure was presented near Anping-Kaohsiung coast in Mode1, which indicated that surface currents have changed with sea surface high of west side of Luzon Strait. Surface currents were showed northward current structure in the SWT in Mode2. Surface currents were showed northeastward current structure in the South of Penghu Islands in Mode3, which was affected by the northeast monsoon in this area. In addition, when Mode2 and Mode3 combined with each other, they can obtain a propagating mode in the SWT. The main propagating features propagated cyclonic or anti-cyclonic rotation currents between the Anping-Kaohsiung and Penghu Islands. The propagating direction was determined by the phase trajectory of mode amplitude in the Mode2 and Mode3. If phase trajectory was clockwise, the strong NE monsoon would counter the northward current in the SWT. The results in the South of the Penghu Islands have produced the cyclonic rotation currents, and have propagated to the coast of Anping-Kaohsiung. When the phase trajectory was counterclockwise, and the NE monsoon weakened, southward and northeastward current structure was presented in the Southern of SWT and South of Penghu Islands respectively. The results near the coast of Anping-Kaohsiung have produced the anti-cyclonic rotation currents, and have propagated to the South of the Penghu Islands.
Subjects
Sea southwest of Taiwan
Surface currents
HF Radar
Type
thesis
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