• Atmosphere
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• v.32 no.1
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• pp.39-49
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• 2022

The relationship between the Quasi-Biennial Oscillation (QBO) and the surface air temperature (SAT) in the Korean Peninsula is investigated for the period of 1979~2019. The QBO shows a statistically significant causal relationship with the Korean SAT in early spring when the El Niño-Southern Oscillation (ENSO)'s effect is relatively weak. In particular, when the QBO wind at 70 hPa is westerly, the Korean SAT becomes colder than normal in March. This relationship in March, which is statistically significant, is valid not only for March QBO but also for February QBO, indicating that the QBO is leading the Korean SAT. The Granger causality test indeed shows a causal relationship between February QBO and March Korean SAT. The QBO-Korean SAT relationship is more pronounced in the southeastern part of the Korean Peninsula. As the QBO-related circulation anomalies are evident in the North Pacific and the eastern Eurasia, they induce the horizontal temperature advection to the southeastern part of the Korean Peninsula. This result suggests that the QBO could be useful for improving seasonal prediction of the Korean SAT in March.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.2
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• pp.159-174
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• 2022

Flow prediction was carried out through observational survey and three dimensional multi-layered numerical diagnostic model experiment to clarify the time and spatial structure of tidal current and residual flow dominant in the sea exchange and material circulation of the waters around Geumo Islands in the southern waters of Korea. The horizontal variation of tidal current is so large that it causes asymmetric tidal mixing due to horizontal eddies and the topographical effect creating convergence and dispersion of flow direction and velocity. Due to strong tidal currents flowing northwest-southeast, counterclockwise and clockwise eddies are formed on the left and right sides of the south of Sori Island. These topographical eddies are created by horizontal turbulence and bottom friction causing nonlinear effects. Baroclinic density flows are less than 5 cm/s at coastal area in summer and the entire sea area in winter. The wind driven currents assuming summer and winter seasonal winds are also less than 5 cm/s and the current flow rate is high in winter. Density current in summer and wind driven current in winter have a relatively greater effect on the net residual flows (tidal residual current + density current + density driven current) around Geumo Islands Sea area.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.5
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• pp.265-277
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• 2019

Using the measured data of waves and shore-line, we reviewed the grand circulation process and seasonal variation of beach cusp at the Mang-Bang beach from the perspective of trapped mode Edge waves known as the driving mechanism of beach cusp. In order to track the temporal and spatial variation trends of beach cusp, we quantify the beach cusp in terms of its wave length and amplitude detected by threshold crossing method. In doing so, we also utilize the spectral analysis method and its associated spectral mean sand wave number. From repeated period of convergence and ensuing splitting of sand waves detected from the yearly time series of spectral mean sand wave number of beach cusp, it is shown that the grand circulation process of beach cusp at Mang-Bang beach are occurring twice from 2017. 4. 26 to 2018. 4. 20. For the case of beach area, it increased by $14,142m^2$ during this period, and the shore-line advanced by 18 m at the northen and southern parts of the Mang-Bang beach whereas the shore-line advanced by 2.4 m at the central parts of Mang-Bang beach. It is also worthy of note that the beach area rapidly increased by $30,345m^2$ from 2017.11.26. to 2017.12.22. which can be attributed to the nature of coming waves. During this period, mild swells of long period were prevailing, and their angle of attack were next to zero. These characteristics of waves imply that the main transport mode of sediment would be the cross-shore. Considering the facts that self-healing capacity of natural beaches is realized via the cross-shore sediment once temporarily eroded. it can be easily deduced that the sediment carried by the boundary layer streaming toward the shore under mild swells which normally incident toward the Mang-Bang beach makes the beach area rapidly increase from 2017.11.26. to 2017.12.22.

• Ocean and Polar Research
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• v.25 no.4
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• pp.503-518
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• 2003

This study examines the relationship among temperature, wind, and sea level pressure to understand recent warming in the vicinity of the Antarctic Peninsula. To do this, the surface air temperature, NCEP/NCAR reanalysis wind data and sea level pressure data for the period of 40 years are analyzed. The 40-year surface air temperature data in the Antarctic Peninsula reveals relatively the larger warming trends for autumn and winter than other seasons. The variability of the surface air temperature in this region is compared with that of the regional atmospheric circulation. The surface air temperature is positively correlated with frequency of northwesterlies and negatively correlated with frequency of southeasterlies. This relation is more evident in the northern tip of the Antarctic Peninsula for autumn and winter. The trend analysis of wind frequency in the study area shows increasing and decreasing trends in the frequency of northwesterlies and southeasterlies, respectively, in the northwestern part of the Weddell Sea for autumn and winter. And also it is found that these winds are closely related with decreasing of sea level pressure in the southeastern region of the Antarctic Peninsula. Furthermore from the seasonal variation of sea level pressure in this area, it may be presumed that decreasing of sea level pressure in the southeastern region of the Antarctic Peninsula is related with warming in the vicinity of the Antarctic Peninsula for autumn and winter. Therefore it can be explained that recent warming in the vicinity of the Antarctic Peninsula is caused by positive feedback mechanism, that is, the process that warming in the vicinity of the Antarctic Peninsula can lead to the decrease of sea level pressure in the southeastern region of the Antarctic Peninsula and these pressure decrease in turn lead to the variation of wind direction in northwestern part of Weddell Sea, again the variation of wind direction enhances the warming in the Antarctic Peninsula.

• Ocean and Polar Research
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• v.38 no.2
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• pp.89-102
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• 2016

In this study, we evaluated the model performance with respect to Sea Surface Temperature (SST) and Net Heat Flux (NHF) by considering the characteristics of seasonal temperature variation and contributing factors and by analyzing heat budget terms in the Northwestern Pacific and East Asian Marginal Seas ($110^{\circ}E-160^{\circ}E$, $15^{\circ}N-60^{\circ}N$) using the HadGEM2-AO historical run. Annual mean SST of the HadGEM2-AO is about $0.065^{\circ}C$ higher than observations (EN3_v2a) from 1950 to 2000. Since 1960, the model has simulated well the long-term variation of SST and the increasing rate of SST in the model ($0.014^{\circ}C/year$) is comparable with observations ($0.013^{\circ}C/year$). Heat loss from the ocean to the atmosphere was simulated slightly higher in the HadGEM2-AO than that in the reanalysis data on the East Asian Marginal Seas and the Kuroshio region. We investigated the causes of temperature variation by calculating the heat budget equation in the two representative regions. In the central part of the Kuroshio axis ($125^{\circ}E-130^{\circ}E$, $25^{\circ}N-30^{\circ}N$: Region A), both heat loss in the upper mixed layer by surface heat flux and vertical heat advection mainly cause the decrease of heat storage in autumn and winter. Release of latent heat flux through the heat convergence brought about by the Kuroshio contributes to the large surface net heat flux. Positive heat storage rate is mainly determined by horizontal heat advection from March to April and surface net heat flux from May to July. In the central part of the subtropical gyre ($155^{\circ}E-160^{\circ}E$, $22^{\circ}N-27^{\circ}N$: Region B), unlike Region A, vertical heat advection predominantly causes the decrease of heat storage in autumn and winter. In spring and summer, surface heat flux contributes to the increase of heat storage in Region B and the period is two times longer than the period for Region A. In this season, shoaling of the mixed layer depth plays an important role in the increase of SST.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.2
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• pp.115-122
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• 1999

Investigation of nutrient movement in soil and soil water is necessary to clarify water purification functions and nutrient circulation within a forest ecosystem. In this study, seasonal changes in the nutrient content of soil and soil water was investigated in Korean white pine(Pinus koraiensis) and Japanese larch(Larix leptolepis) forest applied urea ($150kg\;ha^{-1}$). Soil pH was decreased rapidly in Japanese larch plot for a long period. On the other hand, soil pH was increased slightly in Korean white pine plot. T-C and T-N content were increased in both plots. In Japanes larch plot, exchangeable Ca and Mg contents were decreased remarkably than those in korean white pine plot while exchangeable K was increased rapidly after application. The effect of urea application on exchangeable K was not obvious compared to other cations. The pH, Ca, $NH_4-N$, $NO_3-N$, $SO_4-S$ and Cl concentrations in the sampled soil water at surface soil were increased only temporarily after fertilization, with the only exception of the decrease in pH of the soil water in Japanese larch plot. On the other hand, the peak value of K, Mg concentrations in the soil water was shown between 2 and 5 months after fertilization. The concentrations of Ca, $NO_3-N$, $SO_4-S$ and Cl returned to the values found before fertilization after about 1 month. Those of K, Mg, and $NO_3-N$ after 6-12 months.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.2
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• pp.147-154
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• 2014

Bacteria play an important role in biogeochemical cycles in marine environments and their functional attributes in ecosystems depend primarily on species composition. In this study, seasonal variation of bacterial diversity was investigated by pyrosequencing of 16S rDNA in surface sediment and overlying seawater collected in the south East Sea, planned for the site of $CO_2$ sequestration by the carbon capture and storage (CCS) project. Gammaproteobacteria was dominant in the sediment in most seasons, whereas Alphaproteobacteria was a most dominant group in the overlying water. Thus, the bacterial diversity greatly differ between sediment and seawater samples. On the genus level, bacterial diversity between two habitats was also different. However, the number of genera found over 5% were less than 10 in both habitats and the bacterial community was composed of a number of diverse minor or rare genera. Elevation of $CO_2$ concentration during a $CO_2$ storage process, could result in change of bacterial diversity. Thus, this study will be very useful to access the effect of $CO_2$ on bacterial diversity and to predict functional change of the ecosystem during the process of CCS project.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.3
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• pp.243-249
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• 2000

Seasonal variation in species composition and abundance of shallow water fish off Yongwon, Jinhae in the southern coast of Korea was determined by the analysis of monthly samples collected by a beach seine from January to December, 1998. Among 54 species identified, the resident species such as Favonigobius gymnauchen, Chaenogobius laevis, Pholis nebulosa and juvenile Hyporhamphus intermedius were predominated in abundance. The temporal species such as Sardinella zunasi, Leiognathus nuchalis and Takifugu niphobles were collected between April and September. Mean abundance (322 individuals/1000 $m^2$ or 806 g/1000 $m^2$) was higher than that in the shallow sand surf zone of Teachon, but lower than that in the shallow mud area of Chonsu Bay in the western coast of Korea. A large number of H. intermedius were collected in cold months between November and January. The dominant resident species began to be collected from february, and the number of species and biomass were increased until July. A small number of temporal species were collected and subsequently the abundance was low from August to October when high abundance was expected as in the other shallow waters by recruitment of a large number of juveniles of temporal species. The low abundance in these warm months seemed to be related to the water quality by weak water circulation in this shallow mud area.

• Journal of Plant Biology
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• v.16 no.3_4
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• pp.17-34
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• 1973

The physico-chemical factors, the distribution of chlorophyll and the primary production of the lakes Hwajinpo, Yongrangho, Chunchonho, Uiamho, Soyangho and Changjamot have been studied in order to make ecological comparison among these lakes during summer stagnation period of August to September of 1973. On the basis of the characteristics of these lakes, the lake types have been discussed. Thermocline is observed at 3-4m zone in the lake Changjamot and 4-5m zone in the lake Yongrangho. In the case of lake Hwajinpo and impoundments, the distinct thermal stratification is not observed at the summer stagnation period. As to vertical distribution of dissolved oxygen, a positive heterograde curve is obtained in the lakes Hwajinpo and Yongrangho. In the lake Changjamot the typical clinograde curve and the oxygen depletion in hypolimnion are observed. In the case of impoundments, however, the orthograde curve is observed in the lakes Chunchonho and Uiamho. While in the lake Soyangho, any stratification of the disssolved oxygen is not found. In the brackish lakes, such as lakes Hwajinpo and Yongragho, the salinity of hypolimnion is found to be much higher than that of epilimnion. In the lake Hwajinpo, the salinity of hypolimnion is exhibited 32.7$\textperthousand$, which is nearly the same as sea water. The distribution of nitrogenous compounds and phosphates is found to be high in the lake Changjmot. The silicate is also found in high concentration in the lake Chunchonho, and the distribution of nutrients in the brackish lakes is generally low. As to the vertical distribution of chlorophyll level, the lake Changjamot shows a stratum type and the brackish lakes L-type stratification. In the impoundments, lakes Chunchonho and Uiamho appear to be homogeneous type. Seasonal variation of chlorophyll level in the lake Changjamot is examined from January to September 1973. The vertical distribution of chlorophyll during the period of circulation from January to April is homogeneous type and is stratum type thereafter. The maximum chlorophyll level is 277.4mg/$m^2$ on June 23 and the pattern of seasonal variation of chlorophyll level is comparable to the type of eutrophy. The horizontal distribution of chlorophyll level is studied in the brackish lakes, Hwajinpo and Yongrangho. The pattern of distribution is found to be an irregular type. On the basis of measurements of primary production by means of the carbon-14 method and the distribution of chlorophyll level, it is concluded that the interior part of the lake Hwajinpo and Changjamot are eutrophic and the exterior part of the lake Hwajinpo, lake Yongrangho and the impoundments, lake Uiambo and Soyangho are mesotrophic.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.6
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• pp.617-623
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• 2001

To predict the seasonal variation of dissolved oxygen (DO) in Hakata bay, Japan, possible 20 time-series of different hourly-solar-radiation intensities were generated based on stochastically changing solar radiation intensity, and a numerical simulation on dissolved oxygen (DO) was carried out for each time series by using the Sediment-Water Ecological Model (SWEM). The model, consisting of two sub-models with hydrodynamic and biological models, simulates the circulation process of nutrient between water column and sediment, such as nutrient regeneration from sediments as well as ecological structures on the growth of phytoplankton and zooplankton, The results of the model calibration followed the seasonal variation of observed water quality well, and generated cumulative-frequency-distribution (CFD) curves of daily solar radiation agreed well with observed ones, The simulation results indicated that the exchange of sea water would have a great influence on the DO concentration, and that the concentration could change more than 1 mg/L in a day. This prediction method seems to be an effective way to examine a solution to minimize fishery damage when DO is depleted.