Jin-Yong Jeong

Korea Institute of Ocean Science and Technology

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Ayoung Kim

Seoul National University

Yong Sun Kim

Korea Institute of Ocean Science and Technology

Jae-Seol Shim

Korea Institute of Ocean Science and Technology

Jongmin Jeong

Korea Institute of Ocean Science and Technology

Hyoeun Oh

Korea Institute of Ocean Science and Technology

In-Ki Min

Korea Institute of Ocean Science and Technology

Yongchim Min

Korea Institute of Ocean Science and Technology

Chan Joo Jang

Korea Institute of Ocean Science and Technology

Younggun Cho

Inha University

Jaeik Lee

Korea Institute of Ocean Science and Technology

Cooperative Institutions

Korea Institute of Ocean Science and Technology

Pusan National University

Seoul National University

Korea University

Korea Advanced Institute of Science and Technology

Yonsei University

Hanyang University

Samsung (South Korea)

Korea Maritime and Ocean University

Pohang University of Science and Technology

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Cause of the cold condition over northeast Asia in April 202

Go‐Eun Kim Hyoeun Oh Yong Sun Kim Jun‐Hyeok Son Jongmin Jeong

Although northern Asia's temperature was the fourth highest on record, Northeast Asia was severely damaged agricultural and marine products due to the cold condition in April 2020. Previous studies have shown that the dipole atmospheric circulation over Siberia and the East Sea (also referred to as the Japan Sea) rendered this cold environment. Here we show that the atmospheric structure affecting the cold condition over northeast Asia was a mixed result of the East Atlantic/Western Russia (EAWR) pattern and blocking. The wave train was originated from the vorticity forcing of northwest/central Russia and propagated toward the southeast via the climatologically westerly and northerly flows. Furthermore, the blocking days over Siberia increased approximately ten times in April 2020 than climatology along with the easterly anomaly over Mongolia–northeast China. The blocking occurrence might be connected to wavy westerly at the high latitudes. The strong blocking and EAWR pattern led to the robust dipole atmospheric structure with the prevailing northerly wind in April 2020, thereby causing the cold over northeast Asia. Our results help to understand the cause of the cold condition in April over northeast Asia and its impact on the land and ocean ecosystems.

Siberian High

Westerlies

Anomaly (physics)

Atmospheric Circulation

Forcing (mathematics)

10.5194/egusphere-egu23-10834

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Stereo Camera Localization in 3D LiDAR Maps

2021 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) (2018)

Youngji Kim Jin-Yong Jeong Ayoung Kim

As simultaneous localization and mapping (SLAM) techniques have flourished with the advent of 3D Light Detection and Ranging (LiDAR) sensors, accurate 3D maps are readily available. Many researchers turn their attention to localization in a previously acquired 3D map. In this paper, we propose a novel and lightweight camera-only visual positioning algorithm that involves localization within prior 3D LiDAR maps. We aim to achieve the consumer level global positioning system (GPS) accuracy using vision within the urban environment, where GPS signal is unreliable. Via exploiting a stereo camera, depth from the stereo disparity map is matched with 3D LiDAR maps. A full six degree of freedom (DOF) camera pose is estimated via minimizing depth residual. Powered by visual tracking that provides a good initial guess for the localization, the proposed depth residual is successfully applied for camera pose estimation. Our method runs online, as the average localization error is comparable to ones resulting from state-of-the-art approaches. We validate the proposed method as a stand-alone localizer using KITTI dataset and as a module in the SLAM framework using our own dataset.

Ranging

Depth map

Tracking (education)

10.1109/iros.2018.8594362

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Citations (52)

A study on smoke movement in room fires with various pool fire location

KSME International Journal (2002)

Jin-Yong Jeong Hong Sun Ryou

10.1007/bf02985142

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Citations (8)

Complex urban dataset with multi-level sensors from highly diverse urban environments

The International Journal of Robotics Research (2019)

Jin-Yong Jeong Younggun Cho Young-Sik Shin Hyunchul Roh Ayoung Kim

The high diversity of urban environments, at both the inter and intra levels, poses challenges for robotics research. Such challenges include discrepancies in urban features between cities and the deterioration of sensor measurements within a city. With such diversity in consideration, this paper aims to provide Light Detection and Ranging (LiDAR) and image data acquired in complex urban environments. In contrast to existing datasets, the presented dataset encapsulates various complex urban features and addresses the major issues of complex urban areas, such as unreliable and sporadic Global Positioning System (GPS) data, multi-lane roads, complex building structures, and the abundance of highly dynamic objects. This paper provides two types of LiDAR sensor data (2D and 3D) as well as navigation sensor data with commercial-level accuracy and high-level accuracy. In addition, two levels of sensor data are provided for the purpose of assisting in the complete validation of algorithms using consumer-grade sensors. A forward-facing stereo camera was utilized to capture visual images of the environment and the position information of the vehicle that was estimated through simultaneous localization mapping (SLAM) are offered as a baseline. This paper presents 3D map data generated by the SLAM algorithm in the LASer (LAS) format for a wide array of research purposes, and a file player and a data viewer have been made available via the Github webpage to allow researchers to conveniently utilize the data in a Robot Operating System (ROS) environment. The provided file player is capable of sequentially publishing large quantities of data, similar to the rosbag player. The dataset in its entirety can be found at http://irap.kaist.ac.kr/dataset .

Ranging

Sensor Fusion

10.1177/0278364919843996

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Citations (221)

Comparative Analysis of Sequence Control in Six Series-Connected ITER VS Converters

The Transactions of the Korean Institute of Power Electronics (2014)

Hyunsik Jo Jin-Yong Jeong Jongmin Jo Hanju Cha

This study investigates the structure and operation of the ITER VS converter and proposes a sequence control method for six series-connected VS converters to reduce reactive power. The operation and the proposed sequence control method are verified through RTDS simulation. The ITER VS converter must supply voltage/current to the superconducting magnets for plasma current vertical stabilization, and the four-quadrant operation must proceed without a zero-current discontinuous section. The operation mode of the VS converter is separated into a 12and 6-pulse circulating current and transition modes according to the size of the load current. The output voltage of the unit VS converter is limited because of the rated voltage; however, the superconducting coil must increase the operating output voltage. Thus, the VS converter must be connected in a 6-series to provide the required operating output voltage. The output voltage of the VS converters is controlled continuously; however, reactive power is limited within a minimized value of the grid. In this study, the unit converter is compared with converters connected in a 6-series to determine a suitable sequence control method. The output voltage is the same in all cases, but the maximum reactive power is reduced from 100% to 73%. This sequence control method is verified through RTDS simulation.

10.6113/tkpe.2014.19.5.399

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Classification and Causes of East Asian Marine Heatwaves during Boreal Summer

Journal of Climate (2022)

Hyoeun Oh Go‐Eun Kim Yong Sun Kim Jae‐Heung Park Chan Joo Jang

Abstract Marine heatwaves (MHWs) are among the most severe climatic events under global warming conditions; they damage marine ecosystems and result in socioeconomic losses. In East Asia, the sea surface temperature (SST) has increased significantly and is projected to increase further. Considering such increases in SST over East Asia, studies on MHWs are needed to minimize the damage caused. In this study, we classified the spatiotemporal characteristics of East Asian MHWs during boreal summer with a self-organizing map for 39 years (1982–2020) and determined their unexplored possible mechanisms. Four dominant modes of MHWs across East Asia were identified: the 1) Subtropical Gyre, 2) East China Sea, 3) East Sea/Japan Sea, and 4) Yellow Sea modes. The total annual number of MHW days has increased by about 1.23 days yr −1 . The significant trend is mainly determined by the Subtropical Gyre mode, whereas other modes do not exhibit significant trends. We found that the East China Sea mode could be attributed to a strong East Asian summer monsoon via ocean stratification by the low-salinity water from the Yangtze (Changjiang) River. The East Sea/Japan Sea and Yellow Sea modes could be linked to remote forcings over the subtropics, leading to persistent anticyclonic circulation over East Asia. The anomalous anticyclone contributed to the MHW occurrences by enhancing downward shortwave radiation and reducing entrainment cooling caused by Ekman downwelling. These findings have important implications for distinguishing the characteristics of East Asian MHWs and reveal the possibility of predicting them by identifying their precursors. Significance Statement This study aimed to better understand East Asian marine heatwaves (MHWs) and their causes. We utilized a self-organizing map to classify four patterns of MHWs during boreal summer across East Asia—the Subtropical Gyre, East China Sea, East Sea/Japan Sea, and Yellow Sea modes. We found that enhanced shortwave radiation and latent heat flux play an important role in modulating MHWs in East Asia. A reduced vertical-mixing-amplified ocean warming, and the ocean dynamics drove different temporal evolutions of the MHWs among the four modes. We also identified the potential precursors, which would help in improving the future prediction of MHWs in East Asia.

Anticyclone

Downwelling

East Asian Monsoon

10.1175/jcli-d-22-0369.1

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Citations (12)

A Physics-Driven CNN Model for Real-Time Sea Waves 3D Reconstruction

Remote Sensing (2021)

Mara Pistellato Filippo Bergamasco Andrea Torsello Francesco Barbariol Jeseon Yoo

One of the most promising techniques for the analysis of Spatio-Temporal ocean wave fields is stereo vision. Indeed, the reconstruction accuracy and resolution typically outperform other approaches like radars, satellites, etc. However, it is computationally expensive so its application is typically restricted to the analysis of short pre-recorded sequences. What prevents such methodology from being truly real-time is the final 3D surface estimation from a scattered, non-equispaced point cloud. Recently, we studied a novel approach exploiting the temporal dependence of subsequent frames to iteratively update the wave spectrum over time. Albeit substantially faster, the unpredictable convergence time of the optimization involved still prevents its usage as a continuously running remote sensing infrastructure. In this work, we build upon the same idea, but investigating the feasibility of a fully data-driven Machine Learning (ML) approach. We designed a novel Convolutional Neural Network that learns how to produce an accurate surface from the scattered elevation data of three subsequent frames. The key idea is to embed the linear dispersion relation into the model itself to physically relate the sparse points observed at different times. Assuming that the scattered data are uniformly distributed in the spatial domain, this has the same effect of increasing the sample density of each single frame. Experiments demonstrate how the proposed technique, even if trained with purely synthetic data, can produce accurate and physically consistent surfaces at five frames per second on a modern PC.

Temporal resolution

10.3390/rs13183780

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Citations (14)

Assessment of MODIS-Aqua sea surface temperature in the Yellow Sea and East China Seas

American Geophysical Union eBooks (2016)

Jin-Yong Jeong S. Lee Jaebeom Kwon Soohyun Jeong Jae-Chul Noh

China sea

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Simulation of Vertical Water Temperature Structure Variation in the Yellow Sea Typhoon MEARI

Journal of Coastal Research (2018)

Yeong-Yeon Kwon Jin-Yong Jeong Jin‐Yong Choi Jae-Seol Shim Sang-Kwon Hyun

Kwon, Y.-Y.; Jeong, J.-Y.; Choi, J.-Y.; Shim, J.-S., and Kwon, J.-I., 2018. The simulation of vertical water temperature structure variation in the Yellow Sea typhoon MEARI. In: Shim, J.S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1016–1020. Coconut Creek (Florida), ISSN 0749-0208.Typhoon MEARI developed on June 22, 2011 in the eastern Philippines and passed through the central part of Yellow Sea for the first time in the history of meteorological observations. The Korea Institute of Ocean Science and Technology (KIOST) observed surface water temperature, salinity, flow velocity, and the vertical profile of temperature and salinity at a buoy located near the Eocheong Island off the west coast of the Korean Peninsula during Typhoon MEARI (1105). The purpose of this study is to analyze the change of water temperature and velocity characteristics of the typhoon passing through the Yellow Sea and to simulate the changes in the vertical water temperature structure by using numerical model. The Eeocheong observation buoy was used for validation and analysis of the typhoon's wind and surface temperature and for validation of the vertical structure of the currents and the water temperature. The model results show that the surface water temperature decreased and the bottom water temperature increased during the typhoon, similar to the observation results. The model reproduces the tendency of the thermocline to weaken and the mixed layer to thicken as the typhoon passed.

Typhoon

Buoy

Temperature salinity diagrams

Peninsula

10.2112/si85-204.1

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A Regime Shift in the Interhemispheric Teleconnection between the Yellow and East China Seas and The Southeastern Tropical Pacific in The Southern Hemisphere during The Boreal Summer

Research Square (Research Square) (2021)

Yong Sun Kim Minho Kwon Eui‐Seok Chung Sang‐Wook Yeh Jin-Yong Jeong

Abstract Through statistical estimations on reconstructed datasets for the period 1982−2020 after removing a long-term trend, we observed that there was a drastic regime shift in the early summer’s connection between the YECS and the tropical Pacific in the early 2000s. The summer YECS SSTs had seemed to be modulated by local oceanic and atmospheric processes along with their marginal coupling to the tropical Pacific during the pre-2003 period before the regime shift. In contrast, an interhemispheric YECS−tropical southeastern Pacific (SEP) coupling appeared after the regime shift. This teleconnection was at least partially attributed to a reduced El Niño signature in the tropical Pacific, which favors the emergence of the South Pacific meridional mode (SPMM) independently from ENSO signals. Precipitation anomalies in the western tropical Pacific act as an atmospheric bridge to mediate the air-sea interacted variability associated with the SPMM into the North Pacific. The susceptibility of the YECS to atmospheric forcing may highlight the role of SST over the YECS as a potential indicator of basin-scale climate changes.

Teleconnection

Regime shift

Tropical Atlantic

Walker circulation

Tropical Eastern Pacific

10.21203/rs.3.rs-949462/v1

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