• 지구물리와물리탐사
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• 제26권4호
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• pp.238-267
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• 2023

지구자전과 조석현상에 관하여 19세기 이후 현재까지 알려진 주요 내용들을 소개하였다. 지구자전속도의 영년적/주기적 변화, 세차운동과 장동, 극운동에 관하여 기술하였으며, 또한 지구의 공전/자전 상태와 빙하기도래의 관련설 - Milankovitch 이론에 대하여 돌아보고, 자전과 긴히 연관된 현상으로서 지구조석에 대하여도 기술하였다. 그리고 몇몇 이론적 상세를 부록에 두었다.

• 한국지구과학회지
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• 제37권7호
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• pp.465-475
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• 2016

본 연구에서는 전구에 걸쳐 나타나는 대기의 일주기 및 반일주기 조석을 최신의 3시간 간격 재분석자료를 이용하여 분석하였다. 선행연구들과는 달리 조석의 공간구조 및 계절성에 대한 분석이 표면으로부터 성층권에 걸쳐 수행되었다. 대부분의 층에서 일주기 조석은 중위도 지역에서 강한 반면, 반일주기 조석은 열대 지역에서 지배적으로 나타난다. 일주기 조석은 각 반구의 겨울철보다 여름철에 그 크기가 강하게 나타나는 강한 계절적 변동성을 보인다. 반면에 반일주기 조석은 계절적 변동성을 보이지 않는다. 반일주기 조석은 연직구조를 거의 가지지 않으나, 일주기 조석은 높이에 따라 그 크기가 증가하는 뚜렷한 연직구조를 가진다. 특히 열대지역 일주기 조석은 표면과 자유 대류권, 상층 성층권에서 거의 반대의 위상을 보인다. 그 크기 역시 고도에 따라 비선형적으로 변화하여 수증기, 오존, 중력파 그리고 태양복사에 영향을 받았을 가능성을 시사한다.

• 지구물리와물리탐사
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• 제14권2호
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• pp.133-139
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• 2011

지구조석을 계산하는데 있어 가장 주요한 항은 달이나 태양에 의한 구면조화차수가 2인 항으로서 지구조석의 약 98%를 이루며, 나머지는 3차 이상의 고차 항들이다. 그런데 차수 3항과 그 이상의 고차수의 항들의 값들은 차수 2항과는 다른 상수가 각각 곱하여져서 계산되어야 한다. 본 연구에서는 조석에 의한 중력변화, 변위 및 수직선의 변화에 대한 바른 계산을 검토하였으며, 필요한 관련상수들을 다시 구하였다. 동일차수내의 다른 계수의 조화함수적 조석주기의존성을 토의하였다. 한편, 지구조석을 계산하는데 관련된 중요한 개념들을 요약 소개하였다.

• 자원환경지질
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• 제31권2호
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• pp.141-147
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• 1998

Earth tide observations were taken at AMIST observatory in Seoul by LaCoste-Romberg ET gravimeter from September 2 to 16, 1997 for determining the gravimetric factor ($\delta$) and analyzing the tidal components. Meter drifts were corrected by regression and then denoised by threshholding wavelet, a data processing tool. The mean value of $\delta$ is 1.2 and the mean phase lag of & ($M_2$, $S_2$) and & $K_1$, $O_1$) is $0.07{\pm}0.03^{\circ}$ and $0.08{\pm}0.07^{\circ}$ by analyzing the observed earth tides. For yielding measurements of gravity accurate to about 0.01 mgal, the Earth tide observations are required by ET meter. The tidal variations are due to the planet's distance and zenith angle. With the exception of Earth-Moon and Earth-Sun mechanism, the possible causes of tidal variations are tectonical, meterological and hydrological perturbations. The long period and broad observations are required for determining the state of art gravimetric factor in Korea.

• 자원환경지질
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• 제32권6호
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• pp.653-660
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• 1999

Any mechanical system has a natural oscillation which can be excited, and the earth is no exception. The earth can oscillate in an indefinite number of normal modes of oscillation, rather like a giant bell. The various free modes are generally sparated into two categoridal modes and toroidal modes. Clearly the toroidal modes will produce no perturvation of the gravity field and no vertical acceleration on the surface of the earth. Hence only spheroidal modes can be detected with a gravimeter. EarthTide gravimeter was installed at AIMST in order to observe free modes of the earth. Eight major earthquakes including chinese earthquake (magnitude 7.3) with free oscillations of the earth are observed during one year (1998. 8. 1∼1999.7.31). And then the earth tides components were eilminated from earthquake records using a numerical Butterworth highpass filter. Spectral analysis of gravity readings repersent that 48 observations of shheroidal modes. The relationships between instrumental observations and theoretical predictions based on the Gutenberg earth model agree well those resulting from free oscillation in Korea.

• ALGAE
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• 제32권2호
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• pp.139-153
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• 2017

The ability of a red tide species to take up nutrients is a critical factor affecting its red tide dynamics and species competition. Nutrient uptake by red tide species has been conventionally measured by incubating nutrient-depleted cells for a short period at 1 or 2 light intensities. This method may be applicable to certain conditions under which cells remain in oligotrophic water for a long time and high nutrients are suddenly introduced. Thus, a new method should be developed that can be applicable to the conditions under which cells are maintained in eutrophicated waters in healthy conditions and experience light and dark cycles and different light intensities during vertical migration. In this study, a new repletion method reflecting these conditions was developed. The nitrate uptake rates of the red tide dinoflagellate Prorocentrum micans originally maintained in nitrate repletion and depletion conditions as a function of nitrate concentration were measured. With increasing light intensity from 10 to $100{\mu}E\;m^{-2}s^{-1}$, the maximum nitrate uptake rate ($V_{max}$) of P. micans increased from 3.6 to $10.8 pM\;cell^{-1}d^{-1}$ and the half saturation constant ($K_{s-NO3}$) increased from 4.1 to $6.9{\mu}M$. At $20{\mu}E\;m^{-2}s^{-1}$, the $V_{max}$ and $K_{s-NO3}$ of P. micans originally maintained in a nitrate repletion condition were similar to those maintained in a nitrate depletion condition. Thus, differences in cells under nutrient repletion and depletion conditions may not affect $K_{s-NO3}$ and $V_{max}$. Moreover, different light intensities may cause differences in the nitrate uptake of migratory phototrophic dinoflagellates.

• 대한원격탐사학회지
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• 제32권6호
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• pp.673-679
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• 2016

본 연구에서는 Geostationary Ocean Color Imager (GOCI)의 수출광량(Water-leaving radiance) 자료와 흡광계수(Absorption Coefficients) 자료를 이용하여 한국 남해에 발생한 Cochlodinium polykrikoides 적조를 탐지하는 방법을 제안한다. C. polykrikoides의 분광스펙트럼을 분석하여, 412 nm에서 555 nm구간 파장대의 수출광 및 흡광 특성을 확인하였고 이를 이용하여 적조지수를 개발하였다. 본 연구에서 제안한 탐지기법은 광학적으로 복잡한 남해에서 발생한 적조를 탐지하였으며, 이러한 결과를 바탕으로 향후 적조 방재에 활용될 수 있을 것이라 판단된다.

• 한국지구과학회지
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• 제30권5호
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• pp.671-681
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• 2009

In the equilibrium theory of tides by Newton, tide on the Earth is a phenomenon driven by differential gravity contributed both by the Sun and the Moon. Due to the direct link of the generic tidal effect to the oceanic tides, college students in the earth science education department are exposed to this theory through oceanography lectures as well as astronomy lectures. Common oceanography textbooks adopt a non-inertial reference frame fixed to the Earth in which the fictitious, centrifugal force appears. This has a potential risk to provide misconceptions among students in various aspects including the followings: 1) this is how Newton originally derived the equilibrium theory of tides, and 2) the tide is a phenomenon appearing only in rotating systems. We show that in astronomy, a much simpler description, which employs the inertial frame, is generally used to explain tides and thus causes less confusion. We argue that the description used in astronomy is preferable both in the viewpoints of simplicity and ease of interpretation. Moreover, on a historical basis, an inertial frame was adopted by Newton in Principia to explain tides. Thus, the description used in astronomy is consistent with Newton's original approach. We also present various astrophysical tides which do not comply with the concept of centrifugal force in general. We therefore argue that the description used in oceanography should be compensated by that in astronomy, due to its complexity, historical inconsistency and limited applicability.

• 한국농공학회지
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• 제14권1호
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• pp.2503-2519
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• 1972

The studies were carried out to find the cause and the quantitative evaluation of sea dike materials loss which is occured during the period of construction works for the tideland reclamation projects on the west coast of Korea. Major subjects to studies were to establish the typical relationships between the tidal flow and the movement of dike materials, the tidal-flow and the erosion, the dike materials and the ratio of material movement(losses), construction methods and the ratio of materials movement (losses). Based on the above subjects, the studies were made for the purpose of obtain the following informations; (1) Collecting and evaluaing the data of dike material losses due to foundation settlement, from designed existing dikes on the west coast. (2) By the field investigation at A-San Sea Dike, Pyong Taek Project, the Comparison would be made by the relationships between the tide velocity and the movement of dike foundation under the natural conditions and the period of construction so that find out the relationship between the dike materials of foundation situation and settlements. With regard to the dike construction works, it is so difficult to calculate the exact quantity of material losses due to the foundation settlements. The major factors that affect the settlement losses of the dike materials are: (1) Topographical variation (2) Swepting the sectional area of dike by the tide velocity. (3) Dumping riprap to the outerside of dike during the period of construction works. (4) Sectional area losses by the cause of occurence of the new tide channels. (5) material losses by the heavy storms. (6) Consolidation settlement by the foundation weakness. (7) Material losses by the earth materials by tide flow. Most hi호 material losses were occured by the Consolidation settlement due to the foundation weakness, the maximum tide velocities due to decrease the cross sectional area of the gaps and erosion of foundation due to the range of tide, Inner and outerside of dike, or dike material loses due to the tide flow. Final conclusion would be obtained by the continuous measurement of consolidation settlement at the stage of final clusure of the dike. (It is scheduled to close on the end of 1972) However, intermediate conclusion can be introduced as follows: (1) The estimation of material(losses) during the period of construction works for the existing sea-dikes up to date were only empirical. The material losses at the general closure for design was estimated at 10% of the riprap, 20% of the earth materials, and 20% of the riprap, 40% of the earth materials at the final closure of the dike. The final closure estimated double quantity to the general closure, but it is still doubt. (2) The ratio of consolidation settlements was found smaller than the calculated quantity. It can be foreseen that settlement speeds is higher thom the calculated speeds. (3) The movement of dike foundation under the natural conditions were not so depends on the geological conditions of the foundation. (4) When the tide velocities was estimated 100 at the normal tide, it was estimated 125 at the high tide and 55 at the low tide. The tide velocities at the low tide shows apparently lower than the high tide and the higher velocities at the deep water depth.

• ALGAE
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• 제32권3호
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• pp.199-222
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• 2017

Occurrence of Cochlodinium polykrikoides red tides have resulted in considerable economic losses in the aquaculture industry in many countries, and thus predicting the process of C. polykrikoides red tides is a critical step toward minimizing those losses. Models predicting red tide dynamics define mortality due to predation as one of the most important parameters. To investigate the roles of heterotrophic protists in red tide dynamics in the South Sea of Korea, the abundances of heterotrophic dinoflagellates (HTDs), tintinnid ciliates (TCs), and naked ciliates (NCs) were measured over one- or two-week intervals from May to Nov 2014. In addition, the grazing impacts of dominant heterotrophic protists on each red tide species were estimated by combining field data on red tide species abundances and dominant heterotrophic protist grazers with data obtained from the literature concerning ingestion rates of the grazers on red tide species. The abundances of HTDs, TCs, and NCs over the course of this study were high during or after red tides, with maximum abundances of 82, 49, and $35cells\;mL^{-1}$, respectively. In general, the dominant heterotrophic protists differed when different species caused red tides. The HTDs Polykrikos spp. and NCs were abundant during or after C. polykrikoides red tides. The mean and maximum calculated grazing coefficients of Polykrikos spp. and NCs on populations of co-occurring C. polykrikoides were $1.63d^{-1}$ and $12.92d^{-1}$, respectively. Moreover, during or after red tides dominated by the phototrophic dinoflagellates Prorocentrum donghaiense, Ceratium furca, and Alexandrium fraterculus, which formed serial red tides prior to the occurrence of C. polykrikoides red tides, the HTDs Gyrodinium spp., Polykrikos spp., and Gyrodinium spp., respectively were abundant. The maximum calculated grazing coefficients attributable to dominant heterotrophic protists on co-occurring P. donghaiense, C. furca, and A. fraterculus were 13.12, 4.13, and $2.00d^{-1}$, respectively. Thus, heterotrophic protists may sometimes have considerable potential grazing impacts on populations of these four red tide species in the study area.