Environment
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Characteristics of Submesoscale Geophysical Turbulence Reported
A KAIST research team has reported some of unique characteristics and driving forces behind submesoscale geophysical turbulence. Using big data analysis on ocean surface currents and chlorophyll concentrations observed using coastal radars and satellites has brought better understanding of oceanic processes in space and time scales of O(1) kilometer and O(1) hour. The outcomes of this work will lead to improved tracking of water-borne materials and performance in global and regional climate prediction models.
In 2012, United States National Aeronautics and Space Administration (NASA) released a movie clip called “Perpetual Oceans”, which visualized ocean circulation obtained from satellite altimeter-derived sea surface height observations over two and a half years. When the movie was released to the public, it received a great deal of attention because the circulation patterns were strikingly similar to “The Starry Night” by Vincent van Gogh.
“Perpetual Oceans” is full of vortical flow patterns describing the oceanic turbulent motions at mesoscale (a scale of 100 km or larger). Meanwhile, Professor Sung Yong Kim from the Department of Mechanical Engineering and his team focused on the study of the oceanic turbulence at sub-mesoscale (space and time scales of 1 to 100 km and hours).
Sub-mesoscale processes are important because they contribute to the vertical transport of oceanic tracers, mass, buoyancy, and nutrients and rectify both the mixed layer structure and upper ocean stratification. These process studies have been primarily based on numerical simulations because traditional in situ ocean measurements can be limited in their capability to resolve the detailed horizontal and vertical structures of these processes.
The team conducted big data analysis on hourly observations of one-year ocean surface current maps and five-year chlorophyll concentration maps, obtained from remote sensing instruments such as coastal high-frequency radars (HFRs) and geostationary ocean color imagery (GOCI) to examine the unique characteristics of oceanic submesoscale processes.
The team analyzed the slope change of the wavenumber energy spectra of the observations in terms of season and sampling directions. Through the analysis, the team proved that energy cascade (a phenomenon in which large-scale energy transfers to small-scale energy or vice-versa during the turbulent energy transit) occurs in the spatial scale of 10 km in the forward and inverse directions. This is driven by baroclinic instability as opposed to the mesoscale eddy-driven frontogenesis at the O(100) km scale based on the observed regional submesoscale circulations.
This work will contribute to the parameterization of physical phenomenon of sub-mesoscale in the field of global high-resolution modeling within ocean physics and atmospheric as well as climate change. Based on the understanding of the principle of sub-mesoscale surface circulation, practical applications can be further derived for radioactivity, oil spill recovery, and marine pollutant tracking.
Moreover, the data used in this research was based on long-term observations on sub-mesoscale surface currents and concentrations of chlorophyll, which may reflect the submesoscale processes actively generated in the subpolar front off the east coast of Korea. Hence, this study can potentially be beneficial for integrated big data analyses using high-resolution coastal radar-derived surface currents and satellite-derived products and motivate interdisciplinary research between ocean physics and biology.
This research was published as two companion papers in the Journal of Geophysical Research: Oceans on August 6, 2018. (doi:10.1002/2016JC012517; doi:10.1002/2017JC013732)
Figure 1.'The Starry Night' of Van Gogh and the 'Perpetual Ocean' created by NASA's Goddard Space Flight Center.
Figure 2. A schematic diagram of the energy cascades in forward and backward directions and the spatial scale where the energy is injected.
Figure 3. A snapshot of the chlorophyll concentration map derived from geostationary ocean color imagery (GOCI) off the east coast of Korea presenting several examples of sub-mesoscale turbulent flows.
Figure 4. Energy spectra of the HFR-derived surface currents and GOCI-derived chlorophyll concentrations and the temporal variability of spectral decay slopes in the cross-shore and along-shore directions.
2018.12.13 View 4824 -
NEREC Summer Program Keeps Fellows Thinking, Engaged in Nuclear Nonproliferation
Nuclear technology is more than just technology. It is the fruit of the most advanced science and technology. It also requires high standards of policymaking and global cooperation for benefiting the technology.
As part of the fifth annual Nuclear Nonproliferation Education and Research Center (NEREC) Summer Fellows Program at KAIST, 24 students from 15 countries participated in six-week intensive education and training program. NEREC is the only university-based center dedicated to nuclear nonproliferation education and research established in 2014.
The program, which provides multidisciplinary lectures and seminars on nuclear technology and policy as well as international relations, was designed to nurture global nuclear technology experts well equipped in three areas: in-depth knowledge of technology, applicability gained from sound policy building, and negotiating for international cooperation. It now has grown into the most popular summer program at KAIST.
During the program from July 6 to August 18, participants were able to engage in enriching and stimulating learning experiences in tandem with policies and technology for the utilization and provision of peaceful and safe nuclear technology.
Participating fellows also had to conduct a group research project on a given topic. This year, they explored nuclear nonproliferation issues in relation to nuclear exports and brainstormed some recommendations for current policy. They presented their outcomes at the 2018 NEREC Conference on Nuclear Nonproliferation. After intensive lecture sessions and group research work, the fellows went off to key policy think-tanks, nuclear research institutes, and research power facilities in Korea, Japan, and China.
“NEREC emphasizes nuclear nonproliferation issues related to civilian nuclear power and the associated nuclear fuel cycle development from the point of technology users. I am very glad that the number of participants are increasing year by year,” said the Director of NEREC Man-Sung Yim, a professor in the Department of Nuclear and Quantum Engineering.
Participants’ majors vary from nuclear engineering to international relations to economics. The fellows divided into two groups of graduate and undergraduate courses. They expressed their deep satisfactory in the multidisciplinary lectures by scholars from KAIST, Seoul National University, and Korea National Defense University.
Many participants reported that they learned a lot, not only about policy and international relations but on the research they are conducting and what the key issues will be in dealing for producing meaningful research work.
Moad Aldbissi from the KTH Royal Institute of Technology is one of the students who shared the same view. He said, “Coming from a technical background in nuclear engineering, I managed to learn a lot about nuclear policy and international relations. The importance of integrating the technical and political fields became even clearer.”
Most students concurred that they recognized how important it was to make international collaboration in this powerful field for each country through this program.
“As an engineering student, I just approached this program like an empty glass in policy areas. While working with colleagues during the program, I came to understand how important it is to make cooperation in these fields for the better result of national development and international relations,” said Thanataon Pornphatdetaudom from the Tokyo Institute of Technology.
To Director Yim, this program is becoming well positioned to educate nuclear policy experts in a number of countries of strategic importance. He believes the continuous supply of these experts will contribute to promoting global nuclear nonproliferation and the peaceful use of nuclear energy while the use of nuclear technology continues.
2018.09.04 View 8888 -
Participation in the 2018 Bio-Digital City Workshop in Paris
(A student make a presentatiion during the Bio-Digital City Workshop in Paris last month.)
KAIST students explored ideas for developing future cities during the 2018 Bio-Digital City Workshop held in Paris last month.
This international workshop hosted by Cité des Sciences et de l'Industrie was held under the theme “Biomimicry, Digital City and Big Data.” During the workshop from July 10 to July 20, students teamed up with French counterparts to develop innovative urban design ideas. Cité des Sciences et de l'Industrie is the largest science museum in Europe and is operated by Universcience, a specialized institute of science and technology in France.
Professor Seongju Chang from the Department of Civil and Environmental Engineering and Professor Jihyun Lee of the Graduate School of Culture Technology Students led the students group.
Participants presented their ideas and findings on new urban solutions that combine biomimetic systems and digital technology. Each student group analyzed a special natural ecosystem such as sand dunes, jellyfish communities, or mangrove forests and conducted research to extract algorithms for constructing sustainable urban building complexes based on the results. The extracted algorithm was used to conceive a sustainable building complex forming a part of the urban environment by applying it to the actual Parisian city segment given as the virtual site for the workshop.
Students from diverse background in both countries participated in this convergence workshop. KAIST students included Ph.D. candidate Hyung Min Cho, undergraduates Min-Woo Jeong, Seung-Hwan Cha, and Sang-Jun Park from the Department of Civil and Environmental Engineering, undergraduate Kyeong-Keun Seo from the Department of Materials Science and Engineering, JiWhan Jeong (Master’s course) from the Department of Industrial and Systems Engineering, Ph.D. candidate Bo-Yoon Zang from the Graduate School of Culture Technology. They teamed up with French students from diverse backgrounds, including Design/Science, Visual Design, Geography, Computer Science and Humanities and Social Science.
This workshop will serve as another opportunity to expand academic and human exchange efforts in the domain of smart and sustainable cities with Europe in the future as the first international cooperation activity of KAIST and the Paris La Villette Science Museum.
Professor Seong-Ju Chang who led the research group said, "We will continue to establish a cooperative relationship between KAIST and the European scientific community. This workshop is a good opportunity to demonstrate the competence of KAIST students and their scientific and technological excellence on the international stage.”
2018.08.01 View 9054 -
2016 KAIST EEWS Workshop
The Energy, Environment, Water and Sustainability (EEWS) Graduate School of KAIST hosted a workshop entitled “Progress and Perspectives of Energy Science and Technology” on October 20, 2016. The workshop took place at the Fusion Hall of the KAIST Institute on campus.
About 400 experts in energy science and engineering participated in the event. Eight globally recognized scientists introduced the latest research trends in nanomaterials, energy theory, catalysts, and photocatalysts and led discussions on the current status and prospects of EEWS.
Professors Yi Cui of Stanford University, an expert in nanomaterials, and William A. Goddard of California Institute of Technology presented their research experiments on materials design and recent results on the direction of theory under the topics of energy and environment.
Dr. Miquel Salmeron, a former head of the Material Science Division of Lawrence Berkeley National Laboratory, and Professor Yuichi Ikuhara of Tokyo University introduced their analysis of catalysts and energy matters at an atomic scale.
Professor Sukbok Chang of the Chemistry Department at KAIST, a deputy editor of ACS Catalysis and the head of the Center for Catalytic Hydrocarbon Functionalizations at the Institute of Basic Science, and Professor Yang-Kook Sun of Energy Engineering at Hanyang University, who is also a deputy editor of ACS Energy Letters, presented their latest research results on new catalytic reaction development and energy storage.
The workshop consisted of three sections which addressed the design of energy and environment materials; analysis of energy and catalytic materials; and energy conversion and catalysts.
The EEWS Graduate School was established in 2008 with the sponsorship of the Korean government’s World Class University (WCU) project to support science education in Korea. Professor J. Fraser Stoddart, the winner of the 2016 Nobel Prize in Chemistry, was previously worked at the KAIST EEWS Graduate School as a WCU visiting professor for two years, from 2011 to 2013. Professor Ali Coskun, who was a postdoctoral researcher in the laboratory of Professor Stoddart, now teaches and conducts research as a full-time professor at the graduate school.
Dean Yousung Jung of the EEWS Graduate School said:
“This workshop has provided us with a meaningful opportunity to engage in discussions on energy science and technology with world-class scholars from all around the world. It is also a good venue for our graduate school to share with them what we have been doing in research and education.”
2016.10.20 View 10843