• Proceedings of the KSRS Conference
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• v.2
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• pp.672-675
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• 2006

The geostrophic current component is estimated from the sea surface velocity observed by the long-range High-Frequency Ocean Radar (HF radar) system in the upstream of the Kuroshio, by comparing with geostrophic velocity determined from along-track T/P and Jason-1 altimetry data. However, the sea surface velocity of the HF radar (HF velocity) contains not only the geostrophic current but also the ageostrophic current such as tidal current and wind-driven Ekman current. Tidal current component is first extracted by the harmonic analysis of the time series of the HF velocity. Then, the Ekman current is further estimated from daily wind data of IFREMER by applying the least-square method to the residual difference between the HF velocity and the altimetry geostrophic velocity. As a result, the Ekman current in the HF velocity is estimated as 1.32 % of the wind speed and as rotated 45$^{\circ}$ clockwise to the wind direction. These parameters are found almost common in the Kuroshio area and in the Open Ocean. After these corrections, the geostrophic velocity component in the HF velocity agrees well with the altimetry geostrophic velocity.

• Journal of the korean society of oceanography
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• v.32 no.1
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• pp.1-7
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• 1997

Surface current fields in the eastern East China Sea (ECS) were constructed by analyzing trajectories of 58 satellite-tracked surface drifters released during 1991-1996. Composite trajectories and 20-minute-by-20-minute box-averaged current vectors show that the basic current pattern composes of: the Kuroshio main stream, which turns eastward toward the Tokara Strait; a northward branch current of the Kuroshio on the ECS outer shelf deeper than 100 m; and an anticyclonic circulation in the northern Okinawa Trough west of Kyushu. The northward branch current sharply changes its direction to the northeast when it crosses a line connecting Cheju Island, Korea and Goto Islands, Japan. The basic pattern of current field changes slightly from winter to summer, and the main axis of the Tsushima Current in the Korea Strait is found to shift seasonally. The drifter experiment does not support the claim that the Yellow Sea Warm Current is separated from the northward branch current on the outer shelf southeast of Cheju Island. We suggest that the use of the term 'Tsushima Current' be limited to the northeast channel flow in the Korea Strait. The new term 'Kuroshio Branch Current' is suggested for the northward branch current on the outer shelf south of Cheju-do, which is separated from the Kuroshio.

• Proceedings of the KSRS Conference
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• v.1
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• pp.475-478
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• 2006

Total primary production resulting from the photosynthetic process can be defined as the amount of organic matter produced in a given period of time. It is proportional to the chlorophyll-a (chl-a) values in the surface layer of the ocean. The MODIS board on Aqua satellite measures visible and infrared radiation in 36 wavebands, providing simultaneous images of chl-a concentration and sea surface temperature (SST) in the upper layer of the sea. The seasonal distribution of chl-a concentration during one year from April 2005 to March 2006 was examined. Light has a role of starting the seasonal cycle. The Kuroshio Current in this area induces many oceanographical features affecting to the change of seasonal control. The chl-a concentration is also seasonal, which is low in summer and high in winter. In summer, the meandering of Kuroshio Current induces strong eddies and increases the chl-a concentration. In autumn, the delayed small autumn bloom occurred until last December due to the Kuroshio Current. When the Kuroshio axis moves far from the coast, the coastal water dominates and increases the concentration even in the winter. The spring bloom starts early at the beginning of March and decreases during the spring.

• 한국해양학회지
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• v.6 no.2
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• pp.99-103
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• 1971

GEK observation had been done in Satsunan sea region (south western region of Kyushu, Japan), mixing sea region of Kuroshio, its count-current and water mass of Eastern China Sea in August 1968. The results are al follows: 1. Observed values by GEK are coincided well with that of ship's drift in the surface water of Kuroshio region. 2. Compared the observed values by GEK with that of dynamic calculation of 800 db, in the eastern area of the surveyed region occupied by Kuroshio water mass, they are coincided well. But not in the western area which is of mixing zone of the Eastern China Sea water mass, Kuroshio and its count-current, showing over 1 knot differences with calculated value are bigger than that of GEK observation.

• Ocean Science Journal
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• v.42 no.2
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• pp.89-102
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• 2007

The surface circulation of northern South China Sea (hereafter SCS) for the period 1987-2005 was studied using the data of more than 500 satellite-tracked drifters and wind data from QuikSCAT. The mean flow directions in the northern SCS except the Luzon Strait (here after LS) during the periods October_March was southwestward, and $April{\sim}September$ northeastward. A strong northwestward intrusion of the Kuroshio through the LS appears during the $October{\sim}March$ period of northeasterly wind, but the intrusion became weak between April and September. When the strong intrusion occurred, the eddy kinetic energy (EKE) in the LS was $388cm^2/s^2$ which was almost 2 times higher than that during the weak-intrusion season. The volume transport of the Kuroshio in the east of the Philippines shows an inverse relationship to that of the LS. There is a six-month phase shift between the two seasonal phenomena. The volume transport in the east of the Philippines shows its peak sis-month earlier faster than that of the LS. The strong Kuroshio intrusion is found to be also related to the seasonal variation of the wind stress curl generated by the north easterly wind. The negative wind stress curl in the northern part of LS induces an anticyclonic flow, while the positive wind stress curl in the southern part of LS induces a cyclonic flow. The northwestward Kuroshio intrusion in the northern part of LS happened with larger negative wind stress curl, while the westward intrusion along $20.5^{\circ}N$ in the center of the LS occurred with weaker negative wind stress curl.

• Journal of the korean society of oceanography
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• v.37 no.3
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• pp.187-195
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• 2002

The characteristics of surface circulation in the Yellow Sea and the East China Sea are discussed by analyzing a great deal of current data observed by 142 sets of mooring buoy and 58 sets of drifters trajectories collected in the Yellow Sea and the East China Sea through domestic and abroad measurements. Some major features are demonstrated as bellow: 1) Tsushima Warm Current flows away from the Kuroshio and has multiple sources in warm half year and comes only from Kuroshio surface water in cold half year. 2) Taiwan Warm Current comes mainly from the Taiwan Strait Water in warm half year and comes from the intruded Kuroshio surface water and branches near 27N in cold half year. 3) The Changjiang Diluted Water turns towards Cheju Island in summer and flows southward along the coastal line in winter. 4) The study sea area is an eddy developing area, especially in the southern area of Cheju Island and northern area of Taiwan.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.610-614
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• 2002

Time-mean and absolute geostrophic velocities of the Kuroshio current south of Japan are derived from TOPEX/Poseidon altimeter data using a Gaussian jet model. When compared with simultaneous measurements from a shipboard acoustic Doppler current profiler (ADCP) at two intersection points, the altimetric and ADCP absolute velocities correlate well with the correlation of 0.55 to 0.74. The time-mean velocity is accurate to 1 cm s$^{-1}$ to 5 cm s$^{-1}$. The errors in the absolute and the mean velocities are similar to those reported previously far other currents. The comparable performance suggests the Gaussian jet model is a promising methodology for determining absolute geostrophic velocities, noting that in this region the Kuroshio does not meander sufficiently, which provides unfavorable environment for the performance of the Gaussian jet model.

• Korean Journal of Remote Sensing
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• v.18 no.5
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• pp.243-253
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• 2002

Time-mean and absolute geostrophic velocities of the Kuroshio current south of Japan are derived from TOPEX/Poseidon altimeter data using a Gaussian jet model. When compared with simultaneous measurements from a shipboard acoustic Doppler current profiler (ADCP) at two intersection points, the altimetric and ADCP absolute velocities correlate well with the correlation coefficient of 0.55 to 0.74. The accuracy of time-mean velocity ranges from 1 cm s$^{-1}$ to 5 cm s$^{-1}$. The errors in the absolute and the mean velocities are similar to those reported previously for other currents. The comparable performance suggests the Gaussian jet model is a promising methodology for determining absolute geostrophic velocities, noting that in this region the Kuroshio does not meander sufficiently and thus provides unfavorable environment for the performance of the Gaussian jet model.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.3
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• pp.13-23
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• 2000

The distributions of dissolved inorganic nutrient contents were investigated along transection line J (30° N) in the eastern East China Sea in December 1993 and August 1994, respectively. The concentrations of nitrate and silicate in the Kuroshio Surface Water (KSW) with high temperature and high salinity were low below 2μM and 5μM, respectively. However, these were increased sharply with depth and ranged from 20 to 40, 45 to 100μM, respectively, in the Kuroshio Intermediate Water (KIW). The relationship between temperature and nutrients suggests that Kuroshio Intermediate Water with rich nutrients were intruded into the bottom water of the outer continental shelf in the East China Sea. The bottom water of the outer continental shelf was made of two end-members mixing; nutrient depleted warm water and nutrient enriched cold water. Based on temperature, salinity and silicate concentration, the nutrients in the bottom water of the outer continental shelf suggusted to be supplied through the vertical mixing of Kuroshio subsurface water in the depth range of 100～400m. Upwelled nutrient rich water appears to be a important source of nutrients for primary production in the continental shelf area of the East China Sea.

• Ocean and Polar Research
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• v.30 no.4
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• pp.373-378
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• 2008

Long-term tide-gauge data from around the Korean Peninsula were reanalyzed. Both the coastal water and the open sea surrounding the Korean Peninsula appeared to have been influenced by global warming. The long-term change in relative sea levels obtained from tidal stations showed a general rising trend, especially near Jeju Island. It is proposed that global warming may have caused shifting of the path of the Kuroshio branch (Tsushima Warm Current) toward Jeju Island, causing a persistent increase in the water levels along the coast of the island over the last few decades.