Sang-Ryong Lee

Seasonal variability of the M2 tide in the seas adjacent to Korea

Abstract Seasonal variability of the M 2 tidal harmonic constants is revealed through analyses of monthly tidal data at 12 representative tidal stations in the seas adjacent to the Korean peninsula. The variability remain systematic over the 9 years (1965–1973) of data analysis with a range comparable to that of the 18.6 year nodal modulation. Spatial inhomogeneity of the seasonal variability in the observed harmonic constants is found to exist. The largest seasonal variability in M 2 appears in the stations located along the Korea Strait. This variability is not explained by the equilibrium theory of tides, and such a variability or irregularities in the harmonic constants are considered as either a noise as done by Cartwright and Amin (1986), Deutsch Hydrography Zeitschrift , 39 , 235–253, or a manifestation of frictional interaction as done by Godin and Gutierrez (1986) Continental Shelf Research , 5 , 379–402 for the Bay of Fundy. Considering the opposite relation between monthly mean sea level differences in Izuhara-Pusan section and tidal characteristics in the Korea Strait, it is hypothesized that the interaction between the predominant tidal currents and oceanic currents varying with the seasons might be the main cause of the observed temporal variability in the M 2 tide. The nonlinear effect of the Kuroshio is investigated along the shelf break region through scale analyses, which show that the presence of a mean current increases the non-linear terms in the momentum balance by about one order of magnitude. The seasonally different damping effect of the Tsushima Current to the M 2 tide is also discussed to explain the process of dominant seasonal variability along the Korea Strait based on the actual current data, but further thorough investigation, considering the advection effect of the mean current, is required to investigate the associated dynamics more completely.

Energetics of the surface circulation of the Japan/East sea

During the period of August 1987 to June 1998, 96 Argos-tracked drifters traversed through the Japan/East Sea. The displacement data from these drifters were used to compute 1–3 day average current vectors, which described the circulation at 15 m depth. The drifters that passed through the Korea Strait via the western channel were caught by the East Korean Warm Current, and the drifters that passed through the eastern channel were caught by the Tsushima Current. Individual observations of the 3 day average current over 40 cm s−1 were made in the warm waters south of the subpolar front and along the coasts. There was a distinct decrease of eddy energy northward across the subpolar front. Conversion rates of eddy kinetic energy due to eddy mean flow interaction showed significant regions of both dissipation and production.

Tidal Computation of the East China Sea. The Yellow Sea and the East Sea

Abstract The M 2 tidal phenomena in the entire surrounding seas of Korea Peninsula have been investigated under the condition of one model area, majorly to understand which factors govern the amphidromic system in each sub-area. In this study two-dimensional numerical model based upon an implicit scheme has been used. Due to the large depth differences of each sea in the modelled region the tide generating force is included as well as other inertia terms. The model region toward south and south-eastern boundaries is extended to Ryukyu Islands to utilize the measured data. The computed M 2 co-tidal and co-amplitude lines in the Yellow Sea and the East China Sea are in good agreement with those of existing tidal charts. The four amphidromic points known to exist in the Yellow Sea and the East China Sea as well as two amphidromic points in the East Sea (Japan Sea) are successfully reproduced. The results of computation also show that the tide generating forces play greatly different roles in the each sub-sea model region. The tidal amplitude due to the tide generating force explains several percent of the tide generating force in the Yellow Sea and the East China Sea. It is shown that the realistic amphidromic system in the East Sea can not be explained without the tide generating forces. It is inferred that the reflected wave at the head region of Tartary Bay is more reinforced by the tide generating force. Also the role of the driving force at the head of Tartary Bay for the amphidromic system is discussed. An analysis for tidal volume fluxes and volume transport is made for the five straits existing within model area to assess the possible contribution to tidal regime in the linked sub-model area. And the tidal volume fluxes through live straits in the model region are compared with those calculated by simple analytical method (Defant, 1961) and those calculated by Odamaki (1989b).

A Study on the Characteristics of Tropical Cyclone Passage Frequency over the Western North Pacific using Empirical Orthogonal Function

A pattern of tropical cyclone (TC) movement in the western North Pacific area was studied using the empirical orthogonal function (EOF) and the best track data from 1951 to 2007. The independent variable used in this study was defined as the frequency of tropical cyclone passage in 5 by 5 degree grid. The , and modes were the east-west, north-south and diagonal variation patterns. Based on the time series of each component, the signs of first and second mode changed in 1997 and 1991, respectively, which seems to be related to the fact that the passage frequency was higher in the South China Sea for 20 years before 1990s, and recent 20 years in the East Asian area. When the eigen vectors were negative values in the first and second modes and TC moves into the western North Pacific, TC was formed mainly at the east side relatively compared to the case of the positive eigen vectors. The first mode seems to relate to the pressure pattern at the south of Lake Baikal, the second mode the variation pattern around , and the third mode the pressure pattern around Japan. The first mode was also closely related to the ENSO and negatively related to the -3.4 index in the correlation analysis with SST anomalies.

Shoreline-change Rates of the Barrier Islands in Nakdong River Estuary Using Aerial Photography and SPOT-5 Image

Shoreline data of the barrier islands in Nakdong River Estuary for the last three decades were assembled using six sets of aerial photographs and seven sets of satellite images. Canny Algorithm was applied to untreated data in order to obtain a wet-dry boundary as a proxy shoreline. Digital Shoreline Analysis System (DSAS 4.0) was used to estimate the rate of shoreline changes in terms of five statistical variables; SCE (Shoreline Change Envelope), NSM (Net Shoreline Movement), EPR(End Point Rate), LRR (Linear Regression Rate), and LMS (Least Median of Squares). The shoreline in Jinwoodo varied differently from one place to another during the last three decades; the west tail has advanced (i.e., seaward or southward), the west part has regressed, the south part has advanced, and the east part has regressed. After the 2000s, the rate of shoreline changes (?2.5~6.7 m/yr) increased and the east advanced. The shoreline in Shinjado shows a counterclockwise movement; the west part has advanced, but the east part has retreated. Since Shinjado was built in its present form, the west part became stable, but the east part has regressed faster. The rate of shoreline changes (?16.0~12.0 m/yr) in Shinjado is greater than that of Jinwoodo. The shoreline in Doyodeung has advanced at a rate of 31.5 m/yr. Since Doyodeung was built in its present form, the south part has regressed at the rate of ?18.2 m/yr, but the east and west parts have advanced at the rate of 13.5~14.3 m/yr. Based on Digital Shoreline Analysis, shoreline changes in the barrier islands in the Nakdong River Estuary have varied both temporally and spatially, although the exact reason for the shoreline changes requires more investigation.

Observation of the Sea Surface Skin Current Using a GPS-Drifter

A GPS-drifter was newly designed to observe the sea surface skin current and to estimate the direct wind effect on the sea surface. After conducting a test to establish and verify the accuracy of the GPS itself in the laboratory, in-situ experimental campaigns at Saemangeum in Gunsan city and Haeundae in Busan city, Korea, were carried out to ascertain the drifter track and to estimate the velocity data set on Oct. 3, 15, 23, 27 and Nov. 25, 2011. The current meters, RCM9 and ADCP, were moored together to remove the background current field, and the wind data were obtained from several marine stations such as towers and buoys in these areas. The drifter-observed velocity show good agreement with the flow obtained by the HF radar in the Saemangeum area. The direction of the wind-driven current extracted from the drifterobserved velocity was completely deflected to the right, however the degree of the angle was different according to the drift types. The average speed of the wind-driven current matched with 2.19~2.81% of the wind speed and the deflection angle was about 8.0~10.9° without adjustment for the land-sea effect, and about 2.19~2.84% and 4.1~6.0° with the adjustment for the land-sea effect.

Shoreline Change Rate of the Barrier Islands in Nakdong River Estuary over the Southern Part of Korea

ABSTRACT Jeong, S.H.; Khim, B.K..; Jo, Y.H., Kim, B.O., Lee, S.H. and Park, K.S., 2016. Shoreline change rate of the barrier islands in Nakdong River Estuary over the southern part of Korea. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 248–252. Coconut Creek (Florida), ISSN 0749-0208. Shoreline data of the barrier islands in the Nakdong River Estuary in Korea for the last three decades were assembled using six sets of aerial photographs and seven sets of satellite images. Canny Algorithm was applied to untreated data in order to obtain a wet-dry boundary as a proxy shoreline. Digital Shoreline Analysis System (DSAS 4.0) was used to estimate the rate of shoreline changes in terms of three statistical variables; End Point Rate (EPR), Linear Regression Rate (LRR) and Least Median of Squares (LMS). Based on Digital Shoreline Analysis, shoreline changes in the barrier islands in the Nakdong River Estuary have varied both temporally and spatially, although the exact reason for the shoreline changes requires more investigation.

Variation of the summer low SST area in the southwestern coast of Korea

Variation of the low sea surface temperature (LSST) area in the southwestern coast of was analyzed using the daily satellite-observed sea surface temperature data in 2005. The harmonic fitting method was used to separate the long-term variation (= annual + semi-annual components) from the raw data at each grid point, and the residual was estimated by subtracting the longterm component. Investigating the amplitude and phase of tidal components such as Mm and Mf made possible to check the tidal variability of LSST especially in August, and the area of LSST was estimated by comparing the long-term value and linear correlation with lowest SST area. SST was decreased during the spring tide and increased during the neap tide, and the maximum SST difference between the spring and neap was about 5 °C, and horizontal gradient was 0.05–0.1 °C/km in the area. When the LSST area in August was defined by using two conditions: lower SST than the long-term variation and high correlation coefficient with the lowest temperature area at 34.5°N, 125.65°E, it varied with tidal period showing peaks during the spring tide. The area also showed inphase for the Mm and Mf components with 0.9–1.5 °C of amplitude, and especially the phase distribution of Mf showed the elongatedcircular around the lowest temperature area, indicating that the tidal mixing could be a major factor of this phenomenon. The maximum LSST area were 2.69×104, 8.71×103, and 2.62×103 km2 for the correlation coefficients 0.85, 0.90 and 0.95, respectively.