Variability of surface current derived by HF-Radar in the east coast of Korea

Young-Tae Son, Geosystem Research Corporation, Department of Ocean Information Analysis, Gunpo, South Korea and Sung-Tae Jang, Geosystem Research Corporation, Gunpo, South Korea
Abstract:
Surface current derived from the long-range (5 MHz) high-frequency radar (HFR) during 2017 near the east coast of Korea was utilized in order to investigate the jet structure and variability of the East Korea Warm Current (EKWC) exhibiting western boundary current of the open ocean. Meandering, core velocity, width and eddy kinetic energy (EKE) of the EKWC were quantified with the EKWC central position applying concept of center of masses in the geographical and jet coordinates, respectively. A 1-D histogram (at 37.03°N), plotted as representative of all latitudes, shows a little skewed to the east in the center of the Ulleung basing, due to restricted westward movement by the steep and narrow shelf. The peak in the histogram is over the about 1800 m, at a distance of about 70 km from the coast. In the jet coordinate, the time averaged velocity field exhibited a core velocity of about 35 cm/s. The meandering on the geographical time mean, however, produced much smaller variance with a mean jet core velocity reduced by 28 %, indicating that the EKWC is much better detected quantitatively in jet coordinates. Core velocities simultaneously show decreasing trend and seasonal oscillation, similar to fluctuations in other properties (width, meander and EKE). Properties of jet including meander wavelengths and phase speeds will be discussed with underlying physical processes through spectral analysis and Hovemöller diagram.