• Ocean and Polar Research
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• v.43 no.4
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• pp.307-320
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• 2021

Udo Rhodolith Beach is a small-scale, mixed sand-and-gravel beach embayed on the N-S trending rocky coast of Udo, Jeju Island, South Korea. This study analyzes the short-term topographic changes of the beach during the extreme storm conditions of four typhoons from 2016 to 2020: Chaba (2016), Soulik (2018), Lingling (2019), and Maysak (2020). The analysis uses the topographic data of terrestrial LiDAR scanning and drone photogrammetry, aided by weather and oceanographic datasets of wind, wave, current and tide. The analysis suggests two contrasting features of alongshore topographic change depending on the typhoon pathway, although the intensity and duration of the storm conditions differed in each case. During the Soulik and Lingling events, which moved northward following the western sea of the Jeju Island, the northern part of the beach accreted while the southern part eroded. In contrast, the Chaba and Maysak events passed over the eastern sea of Jeju Island. The central part of the beach was then significantly eroded while sediments accumulated mainly at the northern and southern ends of the beach. Based on the wave and current measurements in the nearshore zone and computer simulations of the wave field, it was inferred that the observed topographic change of the beach after the storm events is related to the directions of the wind-driven current and wave propagation in the nearshore zone. The dominant direction of water movement was southeastward and northeastward when the typhoon pathway lay to the east or west of Jeju Island, respectively. As these enhanced waves and currents approached obliquely to the N-S trending coastline, the beach sediments were reworked and transported southward or northward mainly by longshore currents, which likely acts as a major control mechanism regarding alongshore topographic change with respect to Udo Rhodolith Beach. In contrast to the topographic change, the subaerial volume of the beach overall increased after all storms except for Maysak. The volume increase was attributed to the enhanced transport of onshore sediment under the combined effect of storm-induced long periodic waves and a strong residual component of the near-bottom current. In the Maysak event, the raised sea level during the spring tide probably enhanced the backshore erosion by storm waves, eventually causing sediment loss to the inland area.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.178-181
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• 2005

The positioning accuracy of the Global Positioning System (GPS) has been improved considerably during the past two decades. The main error sources such as ionospheric refraction, orbital uncertainty, antenna phase center variation, signal multipath, and tropospheric delay have been reduced substantially, if not eliminated. In this study, the GPS data collected by the GPS receivers that were established as continuously operating reference stations by International GNSS Service (IGS), Ministry of the Interior (MOl), Central Weather Bureau (CWB), and Industrial Technology Research Institute (ITRI) Of Taiwan are utilized to investigate the impact of atmospheric water vapor on GPS positioning determination. The surface meteorological measurements that were concurrently acquired by instruments co-located with the GPS receivers include temperature, pressure and humidity data. To obtain the influence of the GPS height on the proposed impact study. A hydrodynamic ocean tide model (GOTOO.2 model) and solid earth tide were used to improve the GPS height. The surface meteorological data (pressure, temperature and humidity) were introduced to the data processing with 24 troposphere parameters. The results from the studies associated with different GPS height were compared for the cases with and without a priori knowledge of surface meteorological measurements. The finding based on the measurements in 2003 is that the surface meteorological measurements have an impact on the GPS height. The associated daily maximum of the differences is 1.07 cm for the KDNM station. The impact is reduced due to smoothing when the average of the GPS height for the whole year is considered.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.4
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• pp.224-232
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• 2006

This study investigates to detect Sea Surface Temperature (SST) and land cover change after tide embankment construction using Landsat Thematic Mapper (TM) Thermal Infrared (TIR) band data at Shihwa Lake and surrounding area. SST measurement is important for studies of both the structure of the ocean and as the thermal boundary between the ocean and the atmosphere. Since 1970s, the derivation of SST by satellite remote sensing (RS) has been applied to earth surface using Advanced Very High Resolution Radiometer (AVHRR) and Landsat TM. However, AVHRR has restriction in deriving SST in the area whose shoreline is complicated like western coast in South Korea because of coarse spatial resolution. The TIR band of TM images can be used to detect SST change whose shoreline is complicated and narrow like the study site. Thus, multi-temporal TM images were used for SST change detection in this study.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.4
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• pp.777-786
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• 2018

This study propose a new method to detect Cochlodinium polykrikoides on satellite images using logistic regression and decision tree. We used spectral profiles(918) extracted from red tide, clear water and turbid water as training data. The 70% of the entire data set was extracted and used for model training, and the classification accuracy of the model was evaluated by using the remaining 30%. As a result of the accuracy evaluation, the logistic regression model showed about 97% classification accuracy, and the decision tree model showed about 86% classification accuracy.

• Journal of the Korean earth science society
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• v.36 no.6
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• pp.520-532
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• 2015

In order to understand the Holocene sea level changes in the eastern Yellow Sea, the west coast of Korea, and to compare the rates of sea level rise in each period of time, the geological proxy records for pre-instrumental era and measurement data for the present day were combined and analysed. The sea level in the Yellow Sea rose fast with a rate of about 10 mm/yr during the early Holocene, and decelerated down to 1 mm/yr since the mid to late Holocene. The rising rates of sea level in the 20th century were slightly higher than those in the late Holocene. The present-day rates of sea level rise, known as the 'rapid' rise, are in fact much lower or similar, compared to the early to mid Holocene sea levels in the study area. Recent tide-gauge data show that sea level rise in the eastern Yellow Sea has been accelerating toward the 21st century. These rising trends coincide well with global rising patterns in sea level. Additionally, the present-day rising trends of sea level in this study are correlated with increased rates of carbon dioxide concentrations and sea surface temperatures, further indicating a signal to global warming associated with the human effect. Thus, the sea level changes induced by current global warming observed in the eastern Yellow Sea and world's oceans can be considered as 'Anthropocene' sea level changes. The changes in sea level are based on instrumental measurements such as tide-gauges and satellite altimetry, meaning the instrumental era. The Holocene changes in sea level can thus be reconstructed from geological proxy records, whereas the Anthropocene sea-level changes can be solely based on instrumental measurements.

• ALGAE
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• v.31 no.4
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• pp.351-362
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• 2016

We investigated a possible reduction in $CO_2$ uptake rate by phototrophic red tide dinoflagellates arising from mixotrophy. We measured the daily ingestion rates of Prorocentrum minimum by Prorocentrum micans over 5 days in 10 L experimental bottles, and the uptake rates of total dissolved inorganic carbon ($C_T$) by a mixture of P. micans and P. minimum(mixotrophic growth), and for the predator P. micans (phototrophic growth; control) and prey P. minimum (phototrophic growth; control) alone. To account for the effect of pH on the phototrophic growth rates of P. micans and P. minimum, measurements of $C_T$ and pH in the predator and prey control bottles were continued until the pH reached the same level (pH 9.5) as that in the experimental bottles on the final day of incubation. The measured total $C_T$ uptake rate by the mixture of P. micans and P. minimum changed from 123 to $161{\mu}mol\;C_T\;kg^{-1}\;d^{-1}$ over the course of the experiment, and was lower than the $C_T$ uptake rates shown by P. micans and P. minimum in the predator and prey control bottles, respectively, which changed from 132 to $17{\mu}mol\;C_T\;kg^{-1}\;d^{-1}$ over the course of the experiment. The reduction in total $C_T$ uptake rate arising from the mixotrophy of P. micans was 7-31% of the daily $C_T$ uptake rate seen during photosynthesis. The results suggest that red tide dinoflagellates take up less $C_T$ during mixotrophy.

• Journal of the Korean earth science society
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• v.30 no.2
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• pp.247-256
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• 2009

Characteristics of hydrography and tidal currents were investigated in Hampyung Bay through in situ CTD data, tidal currents and elevations. According to the seasonal weather variability, hydrography showed the lower density with high temperature and low salinity in summer and the higher density with low temperature and high salinity in winter. In particular, the thermal structure like a tidal front was formed along the central channel at the neap tide of summer. The critical value of the parameter $SH(=log_{10}(H/U^3)$ where H is depth and U is $M_2$ tidal current amplitude) representing the formation position of tidal front was estimated from 2.4 to 3.5. In addition, the potential energy anomaly $({\phi})$ was ranged between 0.985 and 6.998 Joule/$m^3$, which gradually increased from the mouth into the inner bay. This front may be caused by the unique topography with wide tidal flat and the local difference of tidal current strength. The observed tidal currents at the mouth of bay showed that the ebb time was shorter than the flood time with the increase of depth. This asymmetric ebb-tide dominance is interpreted as a result of tidal distortion by the development of a shallow-water-constituent in Hampyung Bay with a wide macro-tidal flat.

• Korean Journal of Remote Sensing
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• v.39 no.5_1
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• pp.467-479
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• 2023

Satellite altimeters have continuously observed sea surface height (SSH) in the global ocean for the past 30 years, providing clear evidence of the rise in global mean sea level based on observational data. Accurate altimeter-observed SSH is essential to study the spatial and temporal variability of SSH in regional seas. In this study, we used measurements from the Ieodo Ocean Research Station (IORS) and validate SSHs observed by satellite altimeters (Envisat, Jason-1, Jason-2, SARAL, Jason-3, and Sentinel-3A/B). Bias and root mean square error of SSH for each satellite ranged from 1.58 to 4.69 cm and 6.33 to 9.67 cm, respectively. As the matchup distance between satellite ground tracks and the IORS increased, the error of satellite SSHs significantly amplified. In order to validate the correction of the tide and atmospheric effect of the satellite data, the tide was estimated using harmonic analysis, and inverse barometer effect was calculated using atmospheric pressure data at the IORS. To achieve accurate tidal corrections for satellite SSH data in the seas around the Korean Peninsula, it was confirmed that improving the accuracy of tide data used in satellites is necessary.

• ALGAE
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• v.35 no.3
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• pp.225-236
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• 2020

Gymnodinium smaydae is a newly described mixotrophic dinoflagellate that feeds on only Heterocapsa spp. and Scrippsiella acuminata among 19 tested algal prey. It is one of the fastest growing dinoflagellates when feeding, but does not grow well without prey. To investigate its spatial-temporal distributions in Korean waters, we quantified its abundance in water samples that were seasonally collected from 28 stations along the Korean Peninsula from April 2015 to October 2018, using quantitative real-time polymerase chain reactions. This dinoflagellate had a wide distribution, as reflected by the detection of G. smaydae cells at 23 of the sampling stations. However, this distribution had a strong seasonality; it was detected at 21 stations in the summer and only one station in winter. The abundance of G. smaydae was significantly and positively correlated with chlorophyll a concentration as well as with water temperature. However, there were no significant correlations between the abundance of G. smaydae and salinity, concentrations of nutrients, or dissolved oxygen concentration. During the study period, G. smaydae was present when water temperatures were 7.6-28.0℃, salinities were 9.6-34.1, concentrations of NO₃ were not detectable-106.0 μM, and concentrations of PO₄ were not detectable-3.4 μM. The highest abundance of G. smaydae was 18.5 cells mL^-1 in the coastal waters of Jinhae in July 2017 when the chlorophyll a concentration was 127 mg m^-3 and water temperature was 23.8℃. Therefore, the spatial-temporal distribution of G. smaydae in Korean coastal waters may be affected by chlorophyll a concentration and water temperature.

• ALGAE
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• v.31 no.1
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• pp.17-31
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• 2016

To explore the feeding ecology of the newly described heterotrophic dinoflagellate Aduncodinium glandula in the family Pfiesteriaceae, its feeding behavior and prey species were investigated. Additionally, the growth and ingestion rates of A. glandula on the mixotrophic dinoflagellates Heterocapsa triquetra and Akashiwo sanguinea, its optimal and suboptimal prey, respectively were measured. A. glandula fed on prey through a peduncle after anchoring to the prey using a tow filament. A. glandula ate all algal prey and perch blood cells tested and had the most diverse prey species in the family Pfiesteriaceae. Unlike for other pfiesteriacean species, H. triquetra and A. sanguinea support the positive growth of A. glandula. However, the cryptophytes Rhodomonas salina and Teleaulax sp. and the phototrophic dinoflagellate Amphidinium carterae did not support the positive growth of A. glandula. Thus, A. glandula may have a unique kind of prey and its optimal prey differs from that of the other pfiesteriacean dinoflagellates. With increasing mean prey concentration, the growth rates of A. glandula on H. triquetra and A. sanguinea increased rapidly and then slowed or became saturated. The maximum growth rates when feeding on H. triquetra and A. sanguinea were 1.004 and 0.567 d⁻¹, respectively. Further, the maximum ingestion rates of A. glandula on H. triquetra and A. sanguinea were 0.75 and 1.38 ng C predator⁻¹ d⁻¹, respectively. There is no other pfiesteriacean species having H. triquetra and A. sanguinea as optimal and suboptimal prey. Thus, A. glandula may be abundant during blooms dominated by these species not preferred by the other pfiesteriacean dinoflagellates.