• Ocean and Polar Research
• /
• v.24 no.3
• /
• pp.227-236
• /
• 2002

For ten firn cores, from both the eastern and the western side of Lambert Glacier basin (LGB), snow accumulation rate and isotopic temperature were measured far the recent 50 years. Results show that snow accumulation for five cores over the eastern side of LGB (GC30, GD03, GD15, DT001, and DT085) at Wilks Land and Princess Elizabeth Land increases, whereas it decreases at the western side (Core E, DML05, W200, LGB 16, and MGA) at Dronning Maud Land, Mizuho Plateau and Kamp Land. For the past decades, the increasing rate was $0.34-2.36kg\;m^{-2}a^{-1}$ at the eastern side and the decreasing rate was $-0.01\;-\;-2.36kg\;m^{-2}\;a^{-1}$ at the western side. Temperatures at the eastern LGB were also increased with the rate of $0.02%o\;a^{-l}$. At the western LGB it was difficult to see clear trends, which were confirmed by Instrumental temperature records at coastal stations. Although statistic analysis and modeling results display that both surface temperature and accumulation rate has increased trends in Antarctic ice sheet during 1950-2000, the regional distributions were much more different for different geographic areas. We believe that ice-core records at Wilks Land and Princess Elizabeth Land reflect the real variations of SST and moisture change in the southern India Ocean. For the Kamp Land and Dronning Maud Land, however circulation pattern was different, by which the climate was more complicated. The International Trans-Antarctic Scientific Expedition (ITASE) aimed to reveal an overall spatial pattern of climate change over Antarctic ice sheet for the past 200 years. This study points the importance of continental to regional circulation to annual-decadal scale climate change in Antarctica.

• Ocean and Polar Research
• /
• v.40 no.3
• /
• pp.99-114
• /
• 2018

In the present study, we assess the GloSea5 (Global Seasonal Forecasting System version 5) near-surface ocean current forecasts using globally observed surface drifter dataset. Annual mean surface current fields at 0-day forecast lead time are quite consistent with drifter-derived velocity fields, and low values of root mean square (RMS) errors distributes in global oceans, except for regions of high variability, such as the Antarctic Circumpolar Current, Kuroshio, and Gulf Stream. Moreover a comparison with the global high-resolution forecasting system, HYCOM (Hybrid Coordinate Ocean Model), signifies that GloSea5 performs well in terms of short-range surface-current forecasts. Predictions from 0-day to 4-week lead time are also validated for the global ocean and regions covering the main ocean basins. In general, the Indian Ocean and tropical regions yield relatively high RMS errors against all forecast lead times, whilst the Pacific and Atlantic Oceans show low values. RMS errors against forecast lead time ranging from 0-day to 4-week reveal the largest increase rate between 0-day and 1-week lead time in all regions. Correlation against forecast lead time also reveals similar results. In addition, a strong westward bias of about $0.2m\;s^{-1}$ is found along the Equator in the western Pacific on the initial forecast day, and it extends toward the Equator of the eastern Pacific as the lead time increases.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.32 no.2
• /
• pp.173-180
• /
• 2014

The methods for implementing geocentric to geodetic coordinates conversion could be classified into two, which are respectively the closed-form and the iterative-form solutions. Essential conditions to achieve performances are accuracy, speed of convergence and/or simplicity of it's algorithm. Also, the algorithm must be valid at any of inner and outer points in the Earth, including center of Earth, the equatorial plane and the polar axis that are known as 'special regions'. This research planned for evaluating the feasibility of coordinates conversion in special regions, and comparing the accuracy of conversion solutions by using 10 methods for conversions from geocentric to geodetic coordinates. By comparing performances of statistical tests(with accuracy and solving success in special regions), Vermeille(2011) and Karney(2011) methods brought out more satisfied and finer results than other methods.

• Ocean and Polar Research
• /
• v.24 no.1
• /
• pp.1-18
• /
• 2002

Seasonal variation in global transport calculated from an ocean general circulation model (OGCM) has been assessed through the comparison with observational estimates. The OGCM based on the GFDL MOM1.1 has honzontal grid interval of 10 and 21 verticle levels, and was integrated for 31 years forced by climatological wind stress, freshwater flux, and heat flux with restoring. General features of the world ocean circulation are well reproduced, which include the western boundary currents such as the Kuroshio and the Agulhas Current, the Equatorial Current system, the Antarctic Circumpolar Current, and the Weddell Sea gyres. Also well resolved is the remarkable seasonal variation in the depth-integrated flows in the northern Indian Ocean due to the monsoonal wind. Monthly variation is found to be dominant in the transport of the Antarctic Circumpolar Current through the Drake Passage in accordance with observational estimates. It has been shown that the mid-latitude depth-integrated flows obey the Sverdrup relation, except for some regions such as continental shelf regions where the interaction between stratification and bottom topography is critical.

• Ocean and Polar Research
• /
• v.33 no.spc3
• /
• pp.337-347
• /
• 2011

We investigated latitudinal changes in mesozooplankton community structure during a cruise between October 16 and November 30 of 2007 from four distinctive regions in the northwestern Pacific Ocean: Warm pool area (longitude $135^{\circ}$ line), Philippine EEZ (PEEZ), Japan EEZ (JEEZ), and East China Sea (ECS). Major taxa of numerical importance were Clausocalanidae (Clausocalanus spp.), Oncaeidae (Oncaea spp.), and Oithonidae (Oithona spp.) in oligotrophic regions, however Paracalanidae (Paracalanus spp.) was the most abundant group in the ECS. Mesozooplankton size group of <1 mm dominated in PEEZ and WP (48% and 56%, respectively), but mesozooplankton (>1 mm) were of importance in the JEEZ and ECS (34% and 38%, respectively). Mesozooplankton biomass and abundance were high in the JEEZ and ECS, and low in the oligotrophic WP and PEEZ waters, with positive relationship with both total Chl-a and heterotrophic protist biomass. Latitudinal change in mesozooplankton community structure was related with water temperature, with copepods such as Lucicutia spp. and Pleuromamma spp. being present only in warm waters. The geographical expansion of mesozooplankton with a preference for warmer waters could potentially be useful as an indicator for detecting ocean warming.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.82.1-82.1
• /
• 2019

Recent analyses of spectro-images of Saturn observed by Visual and Infrared Mapping Spectrometer (VIMS)/Cassini revealed altitudinal distributions of the spectral structure of haze in Saturn's south-polar regions (Kim et al., 2018) and at $55^{\circ}N$ latitude (Kim et al., 2012). However, other regions of Saturn still have not been investigated. We derived series of high-spatial resolution VIMS images of Saturn's limb at various latitudes. Using our developed code, the altitudinal intensity profiles of $3.3-{\mu}m$ emission and H3+ through different latitudes were plotted. Then we obtained the averaged vertical spectra of $3.3-{\mu}m$ emission which is all blended with fluorescent methane and hydrocarbon haze. The vertically-resolved spectra were measured from the limb of Saturn in 50km intervals to see altitudinal variance. We will present a comparison of spectral structures of $3.3-{\mu}m$ emission with different latitudes. Further investigation using radiative transfer to extract adjacent fluorescent CH4, C2H6, and H3+ is needed to derive spectral structure of pure haze. We look forward to a better understanding of aging process in a global view.

• The Korean Journal of Nuclear Medicine
• /
• v.28 no.2
• /
• pp.172-176
• /
• 1994

As the Tc-99m-MIBI myocardial SPECT demonstrated wide application in the diagnosis of myocardial function, the quantitative and severity-dependent information is currently re quired. In this study, we proposed a computerized method for scoring the fixed defects in terms of extent-weighted severity and for identifying the reversibility in ischemic regions. At the first stage of this method, the transverse slices were reconstructed with 0.4 Nyquist freq. and order 5 Butterworth filter. From the oblique/sagittal slices, maximal count per pixel circumferential profiles were extracted for each sector, and then stress/redist. polar maps were normalized and plotted. For reversibility, the stress polar map was subtracted from the de-layed image and positive-valued pixels were categorized into three grades. The extent-weight-ed severity scores were calculated using the assigned grades and their number of pixels. This procedure was done automatically and the reversibility and severity scores were produced for each of the coronary territories (LAD, RCA, LCX) or any combination of these. Clinical ap-plication has shown that the changes In reversibility scores after PTCA were correlated linearly with the pre PTCA scores(r>0.8) in postinfarct cases as well as in angina, and severity scores of persistent defects in stress/rest SPECT study matched to the regional ejection fraction and visual analysis of regional wall motion of gated blood pool scan(r>0.6). We conclude that the computerized severity scoring method for the analysis of myocardial SPECT could be useful in the assessment of the myocardial ischemia and fixed defect.

• Journal of the Korean Magnetics Society
• /
• v.14 no.3
• /
• pp.89-94
• /
• 2004

We have investigated magnetic properties of monolayer (ML)-thickness Co film deposited on InP(2${\times}$4) reconstruction surface using in situ Surface Magneto-Optical Kerr Effects (SMOKE) measurement system. InP(2${\times}$4) reconstruction surface, obtained by repeated sputtering and annealing, was confirmed by reflection hish energy electron diffraction (RHEED) and scanning tunneling microscope (STM) measurements. From both longitudinal and polar SMOKE measurements, we have observed three distinguishable regions showing different magnetic properties depending on the Co thickness. In the Co film thickness smaller than 7 $m\ell$, no SMOKE signal was detected. In the following thickness between 8 $m\ell$ and 15 $m\ell$, both longitudinal and polar Kerr hysteresis loops were observed, which implies a metastable phase coexisted of in-plane and perpendicular anisotropies. In the film thickness larger than 16 $m\ell$, only longitudinal MOKE signal without polar signal was detected, which implies existence of in-plane anisotropy in this thickness region.

• Ocean and Polar Research
• /
• v.39 no.1
• /
• pp.23-34
• /
• 2017

This study was carried out to investigate the spatial distributions of the macrobenthic communities in the Seomjin River estuary from May, 2015 to May, 2016. The number of species was 163, the mean density was $1,865ind.m^{-2}$, biomass was $204g{\cdot}wet\;m^{-2}$ during this study period. The highest number of species and density appeared among polychaetes whereas the most biomass was contributed by mollusks due to the presence of Corbicula japonica in every season. The study area was divided into 3 regions with similar benthic fauna responding to the gradient of the salinity. Praxillella praetermissa was the dominant species in regions of over 30 psu during all seasons. C. japonica and Hediste diadroma were dominant in the upper regions of the Seomjin River where the salinity was less than 10 psu. Heteromastus filiformis showed the broadest distributional range and dominated in all seasons except for the most upper stream at st. 7. From the result of the Bio-Env analysis, salinity was the most important environmental factor affecting the formation of macrobenthic communities in the study area, and salinity and TOC were the highest contributors to the macrobenthic communities. From the correlation analysis between major dominant species and environmental factors, C. japonica, Prionospio japonica and H. diadroma showed a negative correlation with salinity, while P. praetermissa and Scolectoma longifolia showed a positive correlation. H. filiformis was little affected by salinity but showed a positive correlation with TOC or silt content of sediment.

• Ocean and Polar Research
• /
• v.32 no.4
• /
• pp.411-426
• /
• 2010

The seasonal variations in the zooplankton community of the southern coastal waters of Korea were investigated seasonally in May, August, November 2005, and February 2006. A total of 74 taxa were sampled, with an average abundance ranging from 2,426~23,793 indiv./$m^3$, among which Noctiluca scintillans predominated. Noctiluca scintillans, Acartia omorii, Acartia erythraea, Paracalanus parvus s. l., Centropages abdominalis, Tortanus forcipatus, and Pseudevadne tergestina were the most abundant species detected. Zooplankton diversity was high around the inner regions during the summer, but it was relatively low in the stations located in the outer regions in the autumn. Non-metric multidimensional scaling (nMDS) revealed significant differences in the structures of the zooplankton community among the three regions. Our results showed that the seasonal variations in zooplankton communities in the southern coastal waters of Korea were attributable to seasonal changes in temperature, salinity, chlorophyll a concentrations, and N. scintillans blooms; additionally, this particularly study area might have been specifically influenced by the appearance of the Tsushima Warm Current.