Observations of Surface Currents and Tidal Variability Off of Northeastern Taiwan from Shore-Based High Frequency Radar

Abstract

A network of high-frequency radars (HFRs) has been deployed around Taiwan. The wide-area data coverage is dedicated to revealing near real-time sea-surface current information. This paper investigates three primary objectives: (1) describing the seasonal current synoptic variability; (2) determining the influence of wind forcing; (3) describing the tidal current field pattern and variability. Sea surface currents derived from HFR data include both geostrophic components and wind-driven components. This study explored vector complex correlations between the HFR time series and wind, which was sufficient to identify high-frequency components, including an Ekman balance among the surface currents and wind. Regarding the characteristics of mesoscale events and the tidal field, a year-long high-resolution surface dataset was utilized to observe the current–eddy–tide interactions over four seasons. The harmonic analysis results derived from surface currents off of northeastern Taiwan during 2013 are presented. The results agree well with the tidal parameters estimated from tide-gauge station observations. The analysis shows that this region features a strong, mixed, mainly semidiurnal tide. Continued monitoring by a variety of sensors (e.g., satellite and HFR) would improve the understanding of the circulation in the region.

Multi-Timescale Characteristics of Southwestern Australia Nearshore Surface Current and Its Response to ENSO Revealed by High-Frequency Radar

“…Max : 0.079m/s Min : 0.006m/s Mean : 0.041m/s (A2) Outer Shelf Max : 0.133m/s Min : 0.013m/s Mean : 0.08m/s 0 2 4 6 8 10 12 14 16 18 20…”

“…Most of them focus on characterizing the surface current patterns, such as boundary currents, eddies, oceanic fronts, and near-inertial currents [11][12][13][14]. Some of them investigate the mechanisms of small-scale physical processes, such as the impact of sea surface wind, tide, estuarine flow, and upwelling on the surface currents [15][16][17][18][19][20][21]. In addition, several studies have investigated the small-to medium-scale near-shore processes, such as the cross-shore transport of surface water and the transport of surface biological communities and chemicals [22][23][24], since their transports are of environmental and ecological importance.…”