• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.2
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• pp.318-331
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• 2019

In this study, comparative analysis is performed on the long-term persisted warm eddies that were generated in 2003 (WE03) and in 2014 (WE14) over the East Sea using the HYCOM reanalysis data. The overshooting of the East Korea Warm Current (EKWC) was appeared during the formation period of those warm eddies. The warm eddies were produced in the shallow Korea Plateau region through the interaction of the EKWC and the sub-polar front. In the interior of the both warm eddies, a homogeneous water mass of about $13^{\circ}C$ and 34.1 psu were generated over the upper 150 m depth by the winter mixing. In 2004, the next year of the generation of the WE03, the amount of the inflow through the western channel of the Korea Strait was larger, while the inflow was lesser than its climatology during 2015 corresponding to the development period of the WE14. The above results suggest that the heat and salt are supplied in the warm eddies through the Tsushima Warm Current (TWC), however the amount of the inflow through the Korea Strait has negligible impact on the long-term persistency of the warm eddies. Both of the warm eddies were maintained more than 18 months near Ulleung island, while they have no common feature on the pathways. In the vicinity of the Ulleung basin, large and small eddies are continuously created due to the meandering of the EKWC. The long-term persisted warm eddies in the Ulleung Island seem to be the results of the interaction between the pre-existed eddies located south of the sub-polar front and fresh eddies induced by the meanderings of the EKWC. The conclusion is also in line with the fact that the long-term persisted warm eddies were not always created when the overshooting of the EKWC was appeared.

• The Journal of the Petrological Society of Korea
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• v.24 no.4
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• pp.323-335
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• 2015

Although the Daljeon Basalt in the Pohang Basin is important for interpreting the basin evolution, its relative chronology, stratigraphic position, and isotopic age still remain controversial. In order to clear up the controversies, this study carried out detailed field investigation to determine its distribution and occurrence together with reanalysis of its previous geochemical data and $^{40}Ar/^{39}Ar$ age dating. Based upon the field investigation, the basalt occurring in the central part of the Pohang basin is composed of three main bodies and a dozen of minor dikes and sills that intruded into the Yeonil Group. Their mineral assemblages consist of phenocrysts such as olivine and clinopyroxene and fine groundmasses of clinopyroxene, plagioclase, olivine, and opaque oxide, impling the porphyritic texture of alkaline basalt. All their geochemical data also show the similar geochemical characteristics in TAS, Zr-Ti, and REE/trace elements distribution diagrams. The samples are plotted on alkalic field in the total alkali-versus-silica diagram and show similar patterns to enrichment oceanic basalt or within plate basalt in trace elements. In addition, $^{40}Ar/^{39}Ar$ isochron age of 13.82Ma is obtained. These results indicate that the Daljeon Basalt is an alkaline intrusive rock belonging to the middle Miocene Yeonil Group.

• Journal of Environmental Science International
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• v.18 no.7
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• pp.721-733
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• 2009

To examine the fluctuations of aerosol number concentration with different size in the boundary layer of marine area during summer season, aerosol particles were assayed in the Ieodo Ocean Research Station, which is located 419 km southwest of Marado, the southernmost island of Korea, from 24 June to 4 July, 2008. The Laser Particle Counter (LPC) was used to measure the size of aerosol particles and NCEP/NCAR reanalysis data and sounding data were used to analyze the synoptic condition. The distribution of aerosol number concentration had a large variation from bigger particles more than 3 ${\mu}m$ in diameter to smaller particles more than 1 ${\mu}m$ in diameter with wind direction during precipitation. The aerosol number concentration decreased with increasing temperature. An increase (decrease) of small size of aerosol (0.3${\sim}$0.5 ${\mu}m$ in diameter) number concentration was induced by convergence (divergence) of the wind fields. The aerosol number concentration of bigger size more than 3 ${\mu}m$ in diameter after precipitation was removed as much as 89${\sim}$94% compared with aerosol number concentration before precipitation. It is considered that the larger aerosol particles would be more efficient for scavenging at marine boundary layer. In addition, the aerosol number concentration with divergence and convergence could be related with the occurrence and mechanism of aerosol in marine boundary layer.

• Atmosphere
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• v.22 no.1
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• pp.97-107
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• 2012

To investigate variation of aerosol number concentration at each different size with three-dimensional (3D) wind components in ocean area, aerosol particles and 3D wind components were measured in the Ieodo Ocean Research Station, which is located to 419 km southwest from Marado, the southernmost island of Korea, from 25 June to 8 July 2010. The Laser Particle Counter (LPC) and ultrasonic anemometer were used to measure the size of aerosol particles and 3D wind components (zonal (u), meridional (v), and vertical (w) wind) respectively. Surface weather chart, NCEP/NCAR reanalysis data and sounding data were used to analyze the synoptic condition. The distribution of aerosol number concentration had a large variation from bigger particles more than 1.0 ${\mu}m$ in diameter by wind direction during precipitation. In the number concentration of aerosol particles with respect to the weather conditions, particles larger than 1.0 ${\mu}m$ in size were decreased and sustained to the similar concentration at smaller particles during precipitation. The increase in aerosol number concentration was due to the sea-salt particles which was suspended by southwesterly and upward winds. In addition, the aerosol number concentration with vertical wind flow could be related with the occurrence and increasing mechanism of aerosol in marine boundary layer.

• Journal of the Korean earth science society
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• v.26 no.3
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• pp.268-275
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• 2005

One of the nonlinear statistical modelling, neural network method was applied to predict the Sea Surface Temperature Anomalies (SSTA) in the Nino regions, which represent El Nino indices. The data used as inputs in the training step of neural network model were the first seven empirical orthogonal functions in the tropical Pacific $(120^{\circ}\;E,\;20^{\circ}\;S-20^{\circ}\;N)$ obtained from the NCEP/NCAR reanalysis data. The period of 1951 to 1993 was adopted for the training of neural network model, and the period 1994 to 2003 for the forecasting validation. Forecasting results suggested that neural network models were resonable for SSTA forecasting until 9-month lead time. They also predicted greatly the development and decay of strong E1 Nino occurred in 1997-1998 years. Especially, Nino3 region appeared to be the best forecast region, while the forecast skills rapidly decreased since 9-month lead time. However, in the Nino1+2 region where they are relatively low by the influence of local effects, they did not decrease even after 9-month lead time.

• Journal of Korea Water Resources Association
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• v.50 no.2
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• pp.75-87
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• 2017

In recent decades, extreme events have been significantly increased over the Korean Peninsula due to climate variability and climate change. The potential changes in hydrologic cycle associated with the extreme events increase uncertainty in water resources planning and designing. For these reasons, a reliable changing point analysis is generally required to better understand regime changes in hydrologic time series at watershed scale. In this study, a hierarchical changing point analysis approach that can apply in a watershed scale is developed by combining the existing changing point analysis method and hierarchical Bayesian method. The proposed model was applied to the selected stations that have annual rainfall data longer than 40 years. The results showed that the proposed model can quantitatively detect the shift in precipitation in the middle of 1990s and identify the increase in annual precipitation compared to the several decades prior to the 1990s. Finally, we explored the changes in precipitation and sea level pressure in the context of large-scale climate anomalies using reanalysis data, for a given change point. It was concluded that the identified large-scale patterns were substantially different from each other.

• Korean Journal of Remote Sensing
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• v.34 no.6_1
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• pp.857-868
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• 2018

The microphysics and spatio-temporal distribution of atmospheric aerosols are responsible for estimating the optical properties at a given location. Its accurate estimation is essential to plan efficient simulation for radiative transfer. For this sake, synergetic use of reanalysis data with optics database was used as a potential tool to precisely derive the aerosol model on the basis of the major representative particulates exist within a model grid. In detail, mixing of aerosol types weighted by aerosol optical depth (AOD) components has been developed. This synergetic aerosol model (SAM) is spectrally extended up to $40{\mu}m$. For the major aerosol event cases, SAM showed that the mixed aerosol particles were totally different from the typical standard aerosol models provided by the radiative transfer model. The correlation among the derived aerosol optical properties along with ground-based observation data has also been compared. The current results will help to improve the radiative transfer model simulation under the real atmospheric environment.

• Journal of the Korean earth science society
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• v.40 no.6
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• pp.549-560
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• 2019

The effects of the coal-fired power plant emissions, as the biggest point source of air pollutants, on spatiotemporal surface air pollution over the remote area are investigated in this study, based on a set of date selection and statistical technique to consider meteorological and geographical effects in the emission-concentration (source-receptor) relationship. We here proposed the sophisticated technique of data processing to separate and quantify the effects. The data technique comprises a set of data selection and statistical analysis procedure that include data selection criteria depending on meteorological conditions and statistical methods such as Kolmogorov-Zurbenko filter (K-Z filter) and empirical orthogonal function (EOF) analysis. The data selection procedure is important for filtering measurement data to consider the meteorological and geographical effects on the emission-concentration relationship. Together with meteorological data from the new high resolution ECMWF reanalysis 5 (ERA5) and the Korea Meteorological Administration automated surface observing system, air pollutant emission data from the telemonitoring system (TMS) of Dangjin and Taean power plants as well as spatio-temporal air pollutant concentrations from the air quality monitoring system are used for 4 years period of 2014-2017. Since all the data used in this study have the temporal resolution of 1 hour, the first EOF mode of spatio-temporal changes in air pollutant concentrations over the Seoul metropolitan area (SMA) due to power plant emission have been analyzed to explain over 97% of total variability under favorable meteorological conditions. It is concluded that SO₂, NO₂, and PM₁₀ concentrations over the SMA would be decreased by 0.468, 1.050 ppb, and 2.045 ㎍ m^-3 respectively if SO₂, NO₂, and TSP emissions from Dangjin power plant were reduced by 10%. In the same way, the 10% emission reduction in Taean power plant emissions would cause SO₂, NO₂, and PM₁₀ decreased by 0.284, 0.842 ppb, and 1.230 ㎍ m^-3 over the SMA respectively. Emissions from Dangjin power plant affect air pollution over the SMA in higher amount, but with lower R value, than those of Taean under the same meteorological condition.

• Journal of the Korean earth science society
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• v.44 no.1
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• pp.13-35
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• 2023

Ocean currents play the most important role in causing and controlling global climate change. The water depth of the Yellow Sea is very shallow compared to the East Sea, and the circulation and currents of seawater are quite complicated owing to the influence of various wind fields, ocean currents, and river discharge with low-salinity seawater. The Yellow Sea Warm Current (YSWC) is one of the most representative currents of the Yellow Sea in winter and is closely related to the weather of the southwest coast of the Korean Peninsula, so it needs to be treated as important in secondary-school textbooks. Based on the 2015 revised national educational curriculum, secondary-school science and earth science textbooks were analyzed for content related to the YSWC. In addition, a questionnaire survey of secondary-school science teachers was conducted to investigate their perceptions of the temporal variability of ocean currents. Most teachers appeared to have the incorrect knowledge that the YSWC moves north all year round to the west coast of the Korean Peninsula and is strong in the summer like a general warm current. The YSWC does not have strong seasonal variability in current strength, unlike the North Korean Cold Current (NKCC), but does not exist all year round and appears only in winter. These errors in teachers' subject knowledge had a background similar to why they had a misconception that the NKCC was strong in winter. Therefore, errors in textbook contents on the YSWC were analyzed and presented. In addition, to develop students' and teachers' data literacy, class materials on the YSWC that can be used in inquiry activities were developed. A graphical user interface (GUI) program that can visualize the sea surface temperature of the Yellow Sea was introduced, and a program displaying the spatial distribution of water temperature and salinity was developed using World Ocean Atlas (WOA) 2018 oceanic in-situ measurements of water temperature and salinity data and ocean numerical model reanalysis field data. This data visualization materials using oceanic data is expected to improve teachers' misunderstandings and serve as an opportunity to cultivate both students and teachers' ocean and data literacy.

• Journal of Korea Water Resources Association
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• v.57 no.5
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• pp.333-346
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• 2024

High-resolution medium-range streamflow prediction is crucial for sustainable water quality and aquatic ecosystem management. For reliable medium-range streamflow predictions, it is necessary to understand the characteristics of forcings and to effectively utilize weather forecast data with low spatio-temporal resolutions. In this study, we presented a comparative analysis of medium-range streamflow predictions using the distributed hydrological model, WRF-Hydro, and the numerical weather forecast Global Data Assimilation and Prediction System (GDAPS) in the Geumho River basin, Korea. Multiple forcings, ground observations (AWS&ASOS), numerical weather forecast (GDAPS), and Global Land Data Assimilation System (GLDAS), were ingested to investigate the performance of streamflow predictions with highresolution WRF-Hydro configuration. In terms of the mean areal accumulated rainfall, GDAPS was overestimated by 36% to 234%, and GLDAS reanalysis data were overestimated by 80% to 153% compared to AWS&ASOS. The performance of streamflow predictions using AWS&ASOS resulted in KGE and NSE values of 0.6 or higher at the Kangchang station. Meanwhile, GDAPS-based streamflow predictions showed high variability, with KGE values ranging from 0.871 to -0.131 depending on the rainfall events. Although the peak flow error of GDAPS was larger or similar to that of GLDAS, the peak flow timing error of GDAPS was smaller than that of GLDAS. The average timing errors of AWS&ASOS, GDAPS, and GLDAS were 3.7 hours, 8.4 hours, and 70.1 hours, respectively. Medium-range streamflow predictions using GDAPS and high-resolution WRF-Hydro may provide useful information for water resources management especially in terms of occurrence and timing of peak flow albeit high uncertainty in flood magnitude.