Korean Ocean Research and Development Institute

About: Korean Ocean Research and Development Institute is a facility organization based out in Busan, South Korea. It is known for research contribution in the topics: Sea surface temperature & Gene. The organization has 1770 authors who have published 3032 publications receiving 50142 citations.

Influence of the East Asian winter monsoon on the storm track activity over the North Pacific

Abstract: [1] We investigate the relationship between the East Asian winter monsoon (EAWM) and synoptic eddy activity over the North Pacific Ocean. It is well known that the subtropical Pacific jet becomes stronger during strong monsoon periods than during weak monsoons. The storm track is generally expected to be active when the EAWM is strong, owing to the enhanced subtropical jet. Contrary to this expectation, synoptic eddy activity is significantly reduced in strong EAWM years and, conversely, significantly increased during weak years. In addition, we found that EAWM-induced lower level cooling brings about the reverse relationship: a stronger jet but with weaker storm activities. It is suggested that the local baroclinicity induced by the EAWM modulates the variation of both the jet and North Pacific storm track simultaneously in the interannual time scale. Because major lower level cooling is located in the western parts of both the subtropical jet and the storm track in longitudes and between the two central axes in latitudes, it induces the opposite sign of anomalous local baroclinicity at the two active regions and causes this reverse relationship. The wave seeding from East Asia to the North Pacific storm track is weakened owing to the anomalous lower level cooling in the northwestern Pacific, which also results in reduction of eddy generation and storm track activities.

Refraction tomography using a waveform-inversion back-propagation technique

Abstract: One of the applications of refraction-traveltime tomography is to provide an initial model for waveform inversion and Kirchhoff prestack migration. For such applications, we need a refraction-traveltime tomography method that is robust for complicated and high-velocity-contrast models. Of the many refraction-traveltime tomography methods available, we believe wave-based algorithms to be best suited for dealing with complicated models. We developed a new wave-based, refraction-tomography algorithm using a damped wave equation and a waveform-inversion back-propagation technique. The imaginary part of a complex angular frequency, which is generally introduced in frequency-domain wave modeling, acts as a damping factor. By choosing an optimal damping factor from the numerical-dispersion relation, we can suppress the wavetrains following the first arrival. The objective function of our algorithm consists of residuals between the respective phases of first arrivals in field data and in forward-modeled data. The...

The caligid life cycle: new evidence from Lepeophtheirus elegans reconciles the cycles of Caligus and Lepeophtheirus (Copepoda: Caligidae)

Abstract: The developmental stages of the sea louse Lepeophtheirus elegans (Copepoda: Caligidae) are described from material collected from marine ranched Korean rockfish, Sebastes schlegelii . In L. elegans , setal number on the proximal segment of the antennule increases from 3 in the copepodid to 27 in the adult. Using the number of setae as a stage marker supports the inference that the post-naupliar phase of the life cycle comprises six stages: copepodid, chalimus I, chalimus II, pre-adult I, pre-adult II, and the adult. We observed variation in body length in both of the chalimus stages which we consider represents an early expression of sexual size dimorphism. We interpret the larger specimens of chalimus I as putative females, and the smaller as putative males; similarly with chalimus II, larger specimens are putative females and the smaller are males. Two patterns of life cycle are currently recognized within the Caligidae but the evidence presented here reconciles the two. We conclude that the typical caligid life cycle comprises only eight stages: two naupliar, one copepodid, and four chalimus stages preceding the adult in Caligus , but with the four chalimus stages represented by two chalimus and two pre-adult stages in Lepeophtheirus . This is a profound change with significant implications for the aquaculture industry, given that lice monitoring protocols include counts of chalimus stages and use temperature to predict when they will moult into the more pathogenic, mobile pre-adults. Lice management strategies must be tailored to the precise life cycle of the parasite.