Lagrangian Approach for a New Separation Index of the East Korea Warm Current     

Pak  Gyundo  Kim  Young Ho  Park  Young-Gyu 《Ocean Science Journal》2019,54(1):29-38

Ocean Science Journal - In this study, a separation index for the East Korea Warm Current (EKWC) is defined by Lagrangian particle tracking using surface geostrophic currents based on...  相似文献   

Harmful Dinoflagellate Prorocentrum donghaiense Lu is Widely Distributed Along the East China Sea and Korean Coastal Area     

Shin  Hyeon Ho  Li  Zhun  Seo  Min Ho  Soh  Ho Young  Lim  Weol Ae  Park  Jong Woo 《Ocean Science Journal》2019,54(4):685-691

Ocean Science Journal - There have been controversies regarding the taxonomy of Prorocentrum donghaiense, however Zhang et al. (2016) recently developed a probe with a quantitative real-time PCR...  相似文献   

Numerical simulation of impact loads using a particle method     

B.-H. Lee  J.-C. Park  M.-H. Kim  S.-J. Jung  M.-C. Ryu  Y.-S. Kim 《Ocean Engineering》2010,37(2-3):164-173

The violent free-surface motions interacting with structures are investigated using the moving particle semi-implicit (MPS) method, which was originally proposed by Koshizuka and Oka (1996) for incompressible flow simulation. In the present numerical method, a more efficient algorithm for Lagrangian moving particles is used for solving various highly nonlinear free-surface problems without using the Eulerian approach or the grid system. Therefore, the convection terms and time derivatives in the Navier–Stokes equation can be calculated more directly without any numerical diffusion, instabilities, or topological failure. In particular, the MPS method is applied to the simulation of liquid-entry and slamming problems, such as wet-drop (liquid–liquid collision) tests in an LNG tank and slamming loads (solid–liquid collision) on rigid plates with various incident angles. The numerical results are in good agreement with available experimental data.  相似文献   

Seasonal Variation of Submesoscale Flow Features in a Mesoscale Eddy-dominant Region in the East Sea     

Yeon S. Chang  Byoung-Ju Choi  Young-Gyu Park 《Ocean Science Journal》2018,53(2):191-206

Seasonal changes in the distribution of submesoscale (SM) flow features were examined using a fine-resolution numerical simulation. The SM flows are expected to be strong where mesoscale (MS) eddies actively develop and also when the mixed layer depth (MLD) is deep due to enhanced baroclinic instability. In the East Sea (ES), MS eddies more actively develop in summer while the MLD is deeper in winter, which provided the motivation to conduct this study to test the effects of MLD and MS eddies on the SM activity in this region. Finite-scale Liapunov exponents and the vertical velocity components were employed to analyze the SM activities. It was found that the SM intensity was marked by seasonality: it is stronger in winter when the mixed layer is deep but weaker in summer - despite the greater eddy kinetic energy. This is because in summer the mixed layer is so thin that there is not enough available potential energy. When the SM activity was quantified based on parameterization, (MLD × density gradient), it was determined that the seasonal variation of MLD plays a more important role than the lateral density gradient variation on SM flow motion in the ES.  相似文献   

Comparison of Measurements from Pressure-recording Inverted Echo Sounders and Satellite Altimetry in the North Equatorial Current Region of the Western Pacific     

Chanhyung Jeon  Jae-Hun Park  Dong Guk Kim  Eung Kim  Dongchull Jeon 《Ocean Science Journal》2018,53(2):207-213

An array of 5 pressure-recording inverted echo sounders (PIESs) was deployed along the Jason-2 214 ground track in the North Equatorial Current (NEC) region of the western Pacific Ocean for about 2 years from June 2012. Round-trip acoustic travel time from the bottom to the sea surface and bottom pressure measurements from PIES were converted to sea level anomaly (SLA). AVISO along-track mono-mission SLA (Mono-SLA), reference mapped SLA (Ref-MSLA), and up-to-date mapped SLA (Upd-MSLA) products were used for comparison with PIES-derived SLA (η_tot). Comparisons of η_tot with Mono-SLA revealed that hump artifact errors significantly contaminate the Mono-SLA. Differences of η_tot from both Ref-MSLA and Upd-MSLA decreased as the hump errors were reduced in mapped SLA products. Comparisons of Mono-SLA measurements at crossover points of ground tracks near the observation sites revealed large differences though the time differences of their measurements were only 1.53 and 4.58 days. Comparisons between Mono-SLA and mapped SLA suggested that mapped SLA smooths out the hump artifact errors by taking values between the two discrepant Mono-SLA measurements at the crossover points. Consequently, mapped SLA showed better agreement with η_tot at our observation sites. AVISO mapped sea surface height (SSH) products are the preferable dataset for studying SSH variability in the NEC region of the western Pacific, though some portions of hump artifact errors seem to still remain in them.  相似文献   

Galactic HCO<Superscript>+</Superscript> absorption toward compact extragalactic radio sources     

Geumsook Park  Bon-Chul Koo  Kee-Tae Kim  Do-Young Byun  Carl E. Heiles 《Astrophysics and Space Science》2018,363(7):150

As part of the search for the “dark molecular gas (DMG),” we report on the results of HCO⁺\(J=1\mbox{--}0\) absorption observations toward nine bright extragalactic millimeter wave continuum sources. The extragalactic sources are at high Galactic latitudes (\(|b| > 10^{\circ} \)) and seen at small extinction (\(E(B - V)\lesssim 0.1\) mag). We have detected the HCO⁺ absorption lines toward two sources, B0838+133 and B2251+158. The absorption toward B2251+158 was previously reported, while the absorption toward B0838+133 is a new detection. We derive hydrogen column densities or their upper limits toward the nine sources from our observations and compare them to those expected from CO line emission and far-infrared dust continuum emission. Toward the seven sources with no HCO⁺ detection, CO emission has not been detected, either. Thus the sight lines are likely to be filled with almost pure atomic gas. Toward the two sources with HCO⁺ detection, CO emission has been also detected. Comparison of the H₂ column densities from HCO⁺ absorption and CO emission suggests a non-negligible amount of DMG toward B0838+133.  相似文献   

Improvement of a Doppler-Radiometer Using a Sparse Array     

Hyuk Park Yong-Hoon Kim 《Geoscience and Remote Sensing Letters, IEEE》2009,6(2):229-233

A 2-D Doppler-radiometer has been proposed to improve the poor angular resolution of microwave radiometers, using aperture synthesis on a moving platform. In this letter, we investigate drawbacks of the Doppler-radiometer, which have not been discussed previously in detail. The imaging method is revised to be suitable for imaging of distributed sources, which is the more common situation than a point source, and then the specklelike sidelobes in the point source response are discussed. In distributed source imaging, the specklelike sidelobes in the point source response of the Doppler-radiometer severely degrade the imaging performance, so it is necessary to reduce them. The cause of specklelike sidelobes is discussed, and a sparse array is proposed to improve the imaging performance of the Doppler-radiometer. The improvement is demonstrated by simulation of the point source response, showing reduced speckle.  相似文献   

Change detection and classification of land cover at Hustai National Park in Mongolia     

Uudus Bayarsaikhan  Bazartseren Boldgiv  Kyung-Ryul Kim  Kyung-Ae Park  Donkoo Lee 《International Journal of Applied Earth Observation and Geoinformation》2009

Land cover types of Hustai National Park (HNP) in Mongolia, a hotspot area with rare species, were classified and their temporal changes were evaluated using Landsat MSS TM/ETM data between 1994 and 2000. Maximum-likelihood classification analysis showed an overall accuracy of 88.0% and 85.0% for the 1994 and 2000 images, respectively. Kappa coefficients associated with the classification were resulted to 0.85 for 1994 and 0.82 for 2000 image. Land cover types revealed significant temporal changes in the classification maps between 1994 and 2000. The area has increased considerably by 166.5 km² for mountain steppe and by 12 km² for a sand dune. By contrast, agricultural areas and degraded areas affected by human being activity were decreased by 46.1 km² and 194.8 km² over the 6-year span, respectively. These areas were replaced by mountain steppe area. Specifically, forest area was noticeably fragmented, accompanied by the decrease of ∼400 ha. The forest area revealed a pattern with systematic gain and loss associated with the specific phenomenon called as ‘forest free-south slope’. We discussed the potential environmental conditions responsible for the systematic pattern and addressed other biological impacts by outbreaks of forest pests and ungulates.  相似文献   

Current status and ecological roles of Zostera marina after recovery from large-scale reclamation in the Nakdong River estuary,Korea     

Sang Rul Park  Jong-Hyeob Kim  Chang-Keun Kang  Soonmo An  Ik Kyo Chung  Jeong Ha Kim  Kun-Seop Lee 《Estuarine, Coastal and Shelf Science》2009

Large Zostera marina meadows (covering 13.6 km²) existed in the Nakdong River estuary on the south coast of Korea until the mid-1980s, but these Z. marina beds nearly disappeared due to reclamation of adjacent mud flats for the construction of a port and industrial complex during the late 1980s. Partial recovery of Z. marina meadows occurred recently, and Z. marina coverage of about 0.3 km² was observed in this estuary. In this study, shoot morphology, density, biomass, productivity, and tissue nutrient content were measured to evaluate the current status of the Z. marina meadows by comparing these data to those for persistent seagrass meadows in similar geographical areas. Additionally, we examined the ecological roles of Z. marina in this estuary after recovery from the large-scale disturbance. Shoot density (151 shoots m⁻²) and total biomass (141 g DW m⁻²) in the estuary were similar to those reported from other Z. marina meadows in Korea. Annual leaf production (1726 g DW m⁻² y⁻¹) was higher than generally observed for Z. marina in other geographical areas. These results imply that the existing Z. marina meadows in this estuary have adjusted to local environmental conditions that changed after large-scale reclamation. Estimated annual whole plant carbon (C) and nitrogen (N) incorporations based on shoot production and tissue C and N content were 810.0 g C m⁻² y⁻¹ and 59.7 g N m⁻² y⁻¹, respectively. These values were equivalent to 2.4 × 10⁵ kg C y⁻¹ and 1.8 × 10⁴ kg N y⁻¹ for all Z. marina beds in the Nakdong River estuary. This high C and N incorporation into Z. marina tissues suggests that existing Z. marina meadows play important roles in C and N cycles in this estuary. Although the currently existing Z. marina beds in this estuary are persisting and play an important ecological role, anthropogenic factors that cause seagrass declines still affect the estuary. Thus, effective management and monitoring of Z. marina beds and environmental factors are critical to protecting and conserving this invaluable component of the Nakdong River estuary.  相似文献   

Distribution of Changjiang Diluted Water detected by satellite chlorophyll-a and its interannual variation during 1998–2007     

Hyun-Cheol Kim  Hisashi Yamaguchi  Sinjae Yoo  Jianrong Zhu  Kazumaro Okamura  Yoko Kiyomoto  Katsuhisa Tanaka  Sang-Woo Kim  Taewook Park  Im Sang Oh  Joji Ishizaka 《Journal of Oceanography》2009,65(1):129-135

Sea-viewing Wide Field-of-view Sensor (SeaWiFS) chlorophyll-a distribution in summer in the East China Sea during 1998–2007 was analyzed. Statistical analysis with K-means clustering technique allowed us to define the proper satellite chlorophyll-a concentration indicating the Changjiang Diluted Water (CDW). The spatial distributions of the higher satellite chlorophyll-a concentrations (>0.48 mg m⁻³) corresponded well with the distributions of lower salinity CDW (<30–32) every year. Interannual variation of the CDW area, indicated by the high satellite chlorophyll-a, correlated with the interannual variation of the Changjiang summer freshwater discharge. The correlation analysis indicated that the CDW spread eastward in the East China Sea with a time lag of 1 to 2 months after the discharge.  相似文献