Winter precipitation variability over Korean Peninsula associated with ENSO

In this study, winter precipitation variability associated with the El Niño-Southern Oscillation (ENSO) over the Korean Peninsula was investigated using a 5-pentad running mean data because significant correlation pattern cannot be revealed using seasonal-mean data. It was found a considerably significant positive correlation between Niño3 sea-surface temperature and precipitation during early winter (from Mid-November to early-December), when the correlation coefficient is close to 0.8 in early-December; the correlation is distinctively weakened during late winter. It is demonstrated that such sudden intraseasonal change in relation to ENSO is associated with the presence of anticyclonic flow over the Kuroshio extension region (Kuroshio anticyclone). In early winter, there is strong southerly wind over the Korean Peninsula, which is induced by the Philippine Sea anticyclone and Kuroshio anticyclone. However, in January, although the Philippine Sea anticyclone develops further, the Kuroshio anticyclone suddenly disappears; as a result, the impact of ENSO is considerably weakened over the Korean Peninsula. These results indicate that the Kuroshio anticyclone during El Niño peak phase plays a critical role by strongly affecting Northeast Asia climate, including the Korean Peninsula. In addition, it is also found that there are distinctive interdecadal changes of the relationship between ENSO and precipitation over the Korean Peninsula. In particular, the strong correlation in early winter is clearer in the recent 30 years than that in the previous period of 1950–1979.     

Latitudinal change in benthic foraminiferal fauna by ITCZ movement along the ~131°W transect in the equatorial Pacific Ocean

Modern and fossil benthic foraminifera were examined from nine surface sediments and two piston cores along the ~131°W transect in the equatorial Pacific Ocean. This study was conducted to clarify the biotic response of abyssal benthic foraminifera during the last 220 ka to changes in the seasonal extent of the Intertropical Convergence Zone (ITCZ). The abundance of modern benthic foraminifera was high at stations between the equator and 6°N, whereas it was low at stations north of 6°N, which is generally consistent with the latitudinal CaCO₃ distribution of surface sediments. The northward increase of Epistominella exigua from the equator to ~6°N is similar to the seasonal variations in chlorophyll-a concentrations in the surface water and ITCZ position along ~131°W. This species was more common at core PC5103 (~6°N) than at core PC5101 (~2°N) after ~130 ka, when the Shannon-Wiener diversity (H’) between the two cores started to diverge. Hence, the presentday latitudinal difference in benthic foraminifera (E. exigua and species diversity) between ~2°N and ~6°N along ~131°W has been generally established since ~130 ka. According to the modern relationship between the seasonality of primary production and seasonal ITCZ variations in the northern margin of the ITCZ, the latitudinal divergence of benthic foraminiferal fauna between ~2°N and ~6°N since ~130 ka appear to have been induced by more distinct variations in the seasonal movement of ITCZ.     

Hydrogeochemical Features of Thermal Waters of South Trungbo (Central Vietnam)

The results of studying the features of the hydrogeological structure and chemical and isotope composition of thermal waters from the central part of Vietnam that are characterized by intense manifestations of intrusive magmatism are presented. It is established that low–and high–thermal waters with temperature varying within 30–85°C are developed in the area under study. The value of total mineralization of the hydrotherms ranges from 0.05 to 10.05 g/dm³. It is assumed that the circulation of thermal waters that are different in temperature and chemical composition occurs at two levels. The regular change of the hydrotherm composition in the direction from mineralized chloride sodium, including with increased Ca content, to fresh sodium bicarbonate is revealed. The ratio of δ¹⁸O–δ²H isotopes indicates that the water component is based on meteoric water. In the coastal areas, there is an isotope shift towards the ocean waters, which is also confirmed by the hydrogeochemical data. The key factors for forming the chemical composition of the thermal waters in South Trungbo are their genetic type, the interaction processes in the “water–rock–gas–organic substance” system, and their equilibrium–nonequilibrium state.     

Logistic regression model for sinkhole susceptibility due to damaged sewer pipes

The occurrence of anthropogenic sinkholes in urban areas can lead to severe socioeconomic losses. A damaged underground sewer pipe is regarded as one of the primary causes of such a phenomenon. This study adopted the best subsets regression method to produce a logistic regression model that evaluates the susceptibility for sinkholes induced by damaged sewer pipes. The model was developed by analyzing the sewer pipe network as well as cases of sinkholes in Seoul, South Korea. Among numerous sewer pipe characteristics tested as explanatory variables, the length, age, elevation, burial depth, size, slope, and materials of the sewer pipe were found to influence the occurrence of sinkhole. The proposed model reasonably estimated the sinkhole susceptibility in the area studied, with an area value under the receiver-operating characteristics curve of 0.753. The proposed methodology will serve as a useful tool that can help local governments to choose a cavity inspection regime, and to prevent sinkholes induced by damaged sewer pipes.     

Fostering Environmental Sensitivity by Observing Everyday Environments

This study examined the effects of observing and reflecting on everyday environments in the development of environmental sensitivity, defined as a holistic capability composed of predisposition, knowledge, and behavior subdimensions. We encouraged participants to use diverse sources, such as texts, photographs, and animation, to record their observations and thinking. As a result, the activity in this study was beneficial in enhancing students’ environmental sensitivity. Students’ mean scores on the environmental sensitivity questionnaire improved, and their reflective journals reported increased interest in everyday environments, enhanced knowledge about diverse environmental elements, and strengthened will to act pro-environmentally. The usefulness of the geospatial platform was also reported.     

A Review on Marine N2 Fixation: Mechanism,Evolution of Methodologies,Rates, and Future Concerns

Ocean Science Journal - Investigations on marine N2 fixation have gained momentum since 1960s with eventual establishments of relevant methodologies to identify species involved and quantify the...     

Temperature-Dependent Bifurcated Seasonal Shift of Phytoplankton Community Composition in the Coastal Water off Southwestern Korea

Ocean Science Journal - Coastal water around the archipelago off southwestern Korea has been bathed in an unprecedented pool of warm water in summer in recent years. Here, we examined phytoplankton...     

The Maribo CM2 meteorite fall—Survival of weak material at high entry speed

High entry speed (>25 km s^?1) and low density (<2500 kg m^?3) are the two factors that lower the chance of a meteoroid to drop meteorites. The 26 g carbonaceous (CM2) meteorite Maribo recovered in Denmark in 2009 was delivered by a bright bolide observed by several instruments across northern and central Europe. By reanalyzing the available data, we confirmed the previously reported high entry speed of (28.3 ± 0.3) km s^?1 and trajectory with slope of 31° to the horizontal. In order to understand how such a fragile material survived, we applied three different models of meteoroid atmospheric fragmentation to the detailed bolide light curve obtained by radiometers located in Czech Republic. The Maribo meteoroid was found to be quite inhomogeneous with different parts fragmenting at different dynamic pressures. While 30–40% of the (2000 ± 1000) kg entry mass was destroyed already at 0.02 MPa, another 25–40%, according to different models, survived without fragmentation up to the relatively large dynamic pressures of 3–5 MPa. These pressures are only slightly lower than the measured tensile strengths of hydrated carbonaceous chondrite (CC) meteorites and are comparable with usual atmospheric fragmentation pressures of ordinary chondritic (OC) meteoroids. While internal cracks weaken OC meteoroids in comparison with meteorites, this effect seems to be absent in CC, enabling meteorite delivery even at high speeds, though in the form of only small fragments.     

Effects of flexibility on propulsive force acting on a heaving foil

The hybrid Cartesian/immersed boundary method is applied to simulate effects of flexibility on propulsive force acting on a heaving foil in a viscous flow. Immersed boundary nodes are distributed inside an instantaneous fluid domain. Velocity vector is reconstructed at the immersed boundary node based on an interpolation along a local normal line. Using the staggered/non-staggered grid method, the demand for pressure at boundary nodes is removed. Elastic deformation of the flexible foil is modelled based on the dynamic thin-plate mechanics. The developed code is validated through comparisons with other computations on flow fields around a flapping foil. The generation of the reverse Karman vortex street is investigated. Forces acting on heaving foils are compared for flexible and rigid cases and the increased thrust of the flexible foil is attributed to the deformed configuration near the tip. The flexibility of the heaving foil decreases vertical force and improves propulsion efficiency. The variations of force and deformation are investigated according to bending stiffness of the foil.