• Journal of Korean Society for Atmospheric Environment
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• v.34 no.1
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• pp.101-119
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• 2018

In this study, we analyzed long-term measurements and air quality simulation results of four criteria air pollutants ($PM_{10}$, $O_3$, $NO_2$, and $SO_2$) for 10 years, from 2006 to 2015, with emphasis on trends of annual variabilities. With the observation data, we conducted spatial interpolation using the Kriging method to estimate spatial distribution of pollutant concentrations. We also performed air quality simulations using the CMAQ model to consider the nonlinearity of the secondary air pollutants such as $O_3$ and the influence of long-range transport. In addition, these simulations are used to deduce the effect of long-term meteorological variations on trends of air quality changes because we fixed the emissions inventory while changing meteorological inputs. The nation-wide inter-annual variability of modeled $PM_{10}$ concentrations was $-0.11{\mu}g/m^3/yr$, while that of observed concentrations was $-0.84{\mu}g/m^3/yr$. For the Seoul Metropolitan Area, the inter-annual variability of observed $PM_{10}$ concentrations was $-1.64{\mu}g/m^3/yr$ that is two times rapid improvement compared to other regions. On the other hand, the inter-annual variability of observed $O_3$ concentrations is 0.62 ppb/yr which is larger than the simulated result of 0.13 ppb/yr. Magnitudes of differences between the modeled and observed inter-annual variabilities indicated that decreasing trend of $PM_{10}$ and increasing trend of $O_3$ are more influenced by emissions and oxidation states than meteorological conditions. We also found similar patterns in $NO_2$. However, $NO_2$ trends showed greater regional and seasonal differences than other pollutants. The analytic approach used in this study can be applicable to estimate changes in factors determining air quality such as emissions, weather, and surrounding conditions over a long term. Then analysis results can be used as important data for air quality management planning and evaluation of the chronic impact of air quality.

• Ocean Systems Engineering
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• v.6 no.1
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• pp.23-60
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• 2016

The major objective of this study was to develop further understanding of 3D nearshore hydrodynamics under a variety of wave and tidal forcing conditions. The main tool used was a comprehensive 3D numerical model - combining the flow module of Delft3D with the WAVE solver of XBeach - of nearshore hydro- and morphodynamics that can simulate flow, sediment transport, and morphological evolution. Surf-swash zone hydrodynamics were modeled using the 3D Navier-Stokes equations, combined with various turbulence models (${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES). Sediment transport and resulting foreshore profile changes were approximated using different sediment transport relations that consider both bed- and suspended-load transport of non-cohesive sediments. The numerical set-up was tested against field data, with good agreement found. Different numerical experiments under a range of bed characteristics and incident wave and tidal conditions were run to test the model's capability to reproduce 3D flow, wave propagation, sediment transport and morphodynamics in the nearshore at the field scale. The results were interpreted according to existing understanding of surf and swash zone processes. Our numerical experiments confirm that the angle between the crest line of the approaching wave and the shoreline defines the direction and strength of the longshore current, while the longshore current velocity varies across the nearshore zone. The model simulates the undertow, hydraulic cell and rip-current patterns generated by radiation stresses and longshore variability in wave heights. Numerical results show that a non-uniform seabed is crucial for generation of rip currents in the nearshore (when bed slope is uniform, rips are not generated). Increasing the wave height increases the peaks of eddy viscosity and TKE (turbulent kinetic energy), while increasing the tidal amplitude reduces these peaks. Wave and tide interaction has most striking effects on the foreshore profile with the formation of the intertidal bar. High values of eddy viscosity, TKE and wave set-up are spread offshore for coarser grain sizes. Beach profile steepness modifies the nearshore circulation pattern, significantly enhancing the vertical component of the flow. The local recirculation within the longshore current in the inshore region causes a transient offshore shift and strengthening of the longshore current. Overall, the analysis shows that, with reasonable hypotheses, it is possible to simulate the nearshore hydrodynamics subjected to oceanic forcing, consistent with existing understanding of this area. Part II of this work presents 3D nearshore morphodynamics induced by the tides and waves.

• Korean Journal of Remote Sensing
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• v.39 no.3
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• pp.355-361
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• 2023

Temperature of the Earth's surface is a crucial physical variable in understanding weather and atmospheric dynamics and in coping with extreme heat events that have a great impact on living organismsincluding humans. Thermalsensors on satellites have been a useful meansfor acquiring surface temperature information for wide areas on the globe, and thus characterization of its estimation uncertainty is of central importance for the utilization of the data. Among various factors that affect the estimation, the uncertainty caused by the algorithm itself has not been tested for the atmospheric environment of Korean vicinity. Thisstudy derivesthe uncertainty of the single-channel algorithm under the local atmospheric and oceanic conditions by using reanalysis data and buoy temperature data collected around Korea. Atmospheric profiles were retrieved from two types of reanalysis data, the fifth generation of European Centre for Medium-Range Weather Forecasts reanalysis of the global climate and weather (ERA5) and Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2) to investigate the effect of reanalysis data. MODerate resolution atmospheric TRANsmission (MODTRAN) was used as a radiative transfer code for simulating top of atmosphere radiance and the atmospheric correction for the temperature estimation. Water temperatures used for MODTRAN simulations and uncertainty estimation for the single-channel algorithm were obtained from marine weather buoyslocated in seas around the Korean Peninsula. Experiment results showed that the uncertainty of the algorithm varies by the water vapor contents in the atmosphere and is around 0.35K in the driest atmosphere and 0.46K in overall, regardless of the reanalysis data type. The uncertainty increased roughly in a linear manner as total precipitable water increased.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.4
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• pp.330-336
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• 2018

El $Ni{\tilde{n}}o$ would cause extreme weather conditions, which would result in a negative impact on crop production. The objective of this study was to assess the impact of El $Ni{\tilde{n}}o$ on spring kimchi cabbabe production for the period from 1981- 2016 in South Korea. In this study, years with less than 1.0 Oceanic $Ni{\tilde{n}}o$ index were classified into non El $Ni{\tilde{n}}o$ years. The other years were classified as El $Ni{\tilde{n}}o$ years. The national average production of spring kimchi cabbage in El $Ni{\tilde{n}}o$ years ($3,800kg\;10a^{-1}$) tended to be less than that in non El $Ni{\tilde{n}}o$ years ($4,016kg\;10a^{-1}$). However, there was no significant differences (p = 0.078) in the production between these groups of years. The averaged production of spring kimchi cabbage of El $Ni{\tilde{n}}o$ end years ($3,707{\pm}331kg\;10a^{-1}$) was less than those of El $Ni{\tilde{n}}o$ start years and non El $Ni{\tilde{n}}o$ years by 186 and $309kg\;10a^{-1}$, respectively. Still, such difference was not significant statistically (p=0.127), either. In contrast, there were provinces where the production of spring kimchi cabbage had significant differences by El $Ni{\tilde{n}}o$ occurrence. For example, El $Ni{\tilde{n}}o$ end years had significantly less spring kimchi cabbage production than El $Ni{\tilde{n}}o$ start years and non El $Ni{\tilde{n}}o$ years in Gangwon (p=0.038) and Gyeongbuk (p=0.053) provinces. It appeared that differences in cabbage production resulted from short sunshine duration, which merits further analysis on the impact of extreme weather condtions during El $Ni{\tilde{n}}o$ years on crop production.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.29 no.2
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• pp.77-100
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• 2024

Circulation, tides, currents, harmful algal blooms, water quality, and hypoxic conditions in Jinhae-Masan Bay have been extensively studied. However, these previous studies primarily focused on short-term variations, and there was limited detailed investigation into the physical mechanisms responsible for ocean circulation in the bays. Oceanic processes in the bays, such as pollutant dispersal, changes on a seasonal time scale. Therefore, this study aimed to understand how the circulation in Jinhae-Masan Bay varies seasonally and to examine the effects of tides, winds, and river discharges on regional ocean circulation. To achieve this, a three-dimensional ocean circulation model was used to simulate circulation patterns from 2016 to 2018, and sensitivity experiments were conducted. This study reveals that convective estuarine circulation develops in Jinhae and Masan Bays, characterized by the inflow of deep oceanic water from the Korea Strait through Gadeoksudo, while surface water flows outward. This deep water intrusion divides into northward and westward branches. In this study, the volume transport was calculated along the direction of bottom channels in each region. The meridional water exchange in the eastern region of Jinhae Bay is 2.3 times greater in winter and 1.4 times greater in summer compared to that of zonal exchange in the western region. In the western region of Jinhae Bay, the circulation pattern varies significantly by season due to changes in the balance of forces. During winter, surface currents flow southward and bottom currents flow northward, strengthening the north-south convective circulation due to the combined effects of northwesterly winds and the slope of the sea surface. In contrast, during summer, southwesterly winds cause surface seawater to flow eastward, and the elevated sea surface in the southeastern part enhances northward barotropic pressure gradient intensifying the eastward surface flow. The density gradient and southward baroclinic pressure gradient increase in the lower layer, causing a strong westward inflow of seawater from Gadeoksudo, enhancing the zonal convective circulation by 26% compared to winter. The convective circulation in the western Jinhae Bay is significantly influenced by both tidal current and wind during both winter and summer. In the eastern Jinhae Bay and Masan Bay, surface water flows outward to the open sea in all seasons, while bottom water flows inward, demonstrating a typical convective estuarine circulation. In winter, the contributions of wind and freshwater influx are significant, while in summer, the influence of mixing by tidal currents plays a major role in the north-south convective circulation. In the eastern Jinhae Bay, tidally driven residual circulation patterns, influenced by the local topography, are distinct. The study results are expected to enhance our understanding of pollutant dispersion, summer hypoxic events, and the abundance of red tide organisms in these bays.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.2
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• pp.151-166
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• 1990

Using the data observed on the Oshoro-maru from November 4 to November 12, 1989 in the East China Sea, the oceanographic conditions were investigated. The results are as follows: The oceanographic condition of surface layer was divided into two regions. One was the Tsushima Current Waters and the other was the China Coastal Waters. The oceanic front was formed between above two waters. Tsushima Current Waters had high temperature ranging 22~24$^{\circ}C$, high salinity ranging 33.5~34.5$\textperthousand$ and low D.O less than 4.5ml/l. And China Coastal Waters had low temperature ranging 18~2$0^{\circ}C$, low salinity less than 23.0$\textperthousand$ and high D.O ranging 4.0~5.0ml/l. In the case of the bottom layer, Tsushima Current Waters and China Coastal Waters appeared the same as the surface layer. In addition, the Yellow Sea Bottom Cold Waters and the Southern Bottom Waters of East China Sea distributed together with two surface waters above. The was temperature ranging 15~19$^{\circ}C$, salinity 34.5$\textperthousand$ and low D.O ranging 2.0~3.5ml/l and that was temperature less than 1$0^{\circ}C$, salinity less than 33.3$\textperthousand$ and high D,O greater than 4.5ml/l. The waters of intermediate characteristics between China Coastal Waters and Tsushima Current Waters seem to be resulted from the mixing occurred between the above tow waters, and it had temperature of 20.5~22.$0^{\circ}C$, salinity of 32.3~33.3$\textperthousand$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.1
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• pp.25-39
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• 1990

The distributions of the temperature and salinity in Kamak bay which has two channels and three sea bottom topographic parts were studied by taking the detailed hydrographic data at the ebb and flood during four seasons from May, 1988 to Feb., 1989. The general pattern of the distributions of characteristics which the temperature and salinity has in Kamak bay is basically formed by the topography and sea water movement of the bay. The changes of these distributions by seasons mainly come from the heating and cooling of the sea surface and the increase of the run-off. The bay has three remarkable water masses and the their general characteristics are follows: the inner bay water has a stagnation character influenced by the inland and the concave of the sea bottom in the north west, Yosu harbor water has an estuary character of the low salinity caused by the run-off of Somjin river and Yon Tung brooklet in the north east, and the outer bay water has an out-sea character, as it is located near by the big mouth in the south of the bay. The distributions of those water masses at the ebb and flood show some different features due to the flow patterns, and the daily changes of oceanic conditions at the vicinity of Hangdae-ri are so big that it may influence the habitation and production of the living things in the bay.

• The Korean Journal of Food And Nutrition
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• v.13 no.4
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• pp.334-341
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• 2000

The DMPT produced by marine algae is the main biogenic precursor of oceanic DMS. Also, DMPT is an efficient stimulant for growth, feeding, and body movement of fish and striped prawn, and appears to play a physiologic role as an osmoprotectant in algae. This study was focused on the extraction of dimethyl-$\beta$-propiothetin as bioactive substance from green seaweed. Identification and quantification of dimethyl-$\beta$-propiothetin were measured by headspace gas chromatography after conversion to dimethyl sulfide by treatment with saturated NaOH solution. Dimethyl-$\beta$-propiothetin was extracted through various processes(solvent extraction, ultrasonication, boiling and autoclaving) from Enteromorpha intesinalis. The content of dimethyl-$\beta$-propiothetin extracted by autoclaving treatment showed higher than those of various extraction methods. Dimethyl-$\beta$-propiothetin content in extract of Enteromorpha Enteromorpha was 311,200ng/g after autoclaving at 121$^{\circ}C$ for 60min. Dimethyl-$\beta$-propiothetin in extract of Enteromorpha intestinalis was comparatively stable under low temperature. The retentions of dimethyl-$\beta$-propiothetin content in extract of Enteromorpha intestinalis were 75.8 ~99.8% by incubation at 10~6$0^{\circ}C$ for 2 hours. Chemical decomposition of dimethyl-$\beta$-propiothetin was observed under laboratory conditions at pH values higher than 9.5.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.3
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• pp.236-245
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• 2016

Because microalgae represent high growth rate than terrestrial plants, and it can accumulate significant lipid and carbohydrate content, and other bioactive compounds such as carotenoid and polyphenol in their body, it has been considered as one of the promising resources in bio-energy, and other industries. Although many studies has been performed about the microalgae-derived biochemical accumulation under various abiotic conditions such as different temperatures, salinities and light intensities, the studies about simultaneous effect of those parameters has rarely been performed. Therefore, this study focused on evaluation of simultaneous effect of different salinity (10, 30, 50 psu) and temperatures (20, 25, $30^{\circ}C$) on the changes of biomass, lipid, starch and photosynthetic pigment accumulation. As results, the highest growth rate was achieved at $30^{\circ}C$ and 30 psu in the both algal cultures, and the photosynthetic pigment, chlorophyll a and total carotenoid content, were increased in a temperature-dependent manner. The accumulation of lipid and starch contents exhibited different aspects under different combinations of temperature and salinity. From the results, it is suggested that the changes of microalgal lipid and starch accumulation under different salinities may be affected by the different temperatures.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.5
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• pp.445-457
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• 2017

In this study, we developed an approach to better account for uncertainties in estimated contributions from fine particulate matter ($PM_{2.5}$) modeling. Our approach computes a Concentration Correction Factor (CCF) which is a ratio of observed concentrations to baseline model concentrations. We multiply modeled direct contribution estimates with CCF to obtain revised contributions. Overall, the modeling system showed reasonably good performance, correlation coefficient R of 0.82 and normalized mean bias of 2%, although the model underestimated some PM species concentrations. We also noticed that model biases vary seasonally. We compared contribution estimates of major source sectors before and after applying CCFs. We observed that different source sectors showed variable magnitudes of sensitivities to the CCF application. For example, the total primary $PM_{2.5}$ contribution was increased $2.4{\mu}g/m^3$ or 63% after the CCF application. Out of a $2.4{\mu}g/m^3$ increment, line sources and area source made up $1.3{\mu}g/m^3$ and $0.9{\mu}g/m^3$ which is 92% of the total contribution changes. We postulated two major reasons for variations in estimated contributions after the CCF application: (1) monthly variability of unadjusted contributions due to emission source characteristics and (2) physico-chemical differences in environmental conditions that emitted precursors undergo. Since emissions-to-$PM_{2.5}$ concentration conversion rate is an important piece of information to prioritize control strategy, we examined the effects of CCF application on the estimated conversion rates. We found that the application of CCFs can alter the rank of conversion efficiencies of source sectors. Finally, we discussed caveats of our current approach such as no consideration of ion neutralization which warrants further studies.