Case studies > Dr.Jong-Hwan Yoon interview

Interview with Dr.Jong-Hwan Yoon

Photo of Yoon Dr.Jong-Hwan Yoon
Kyushu University Applied Dynamics Research Center
<Major research themes>
2002.10 – : The deep circulation of the Japan Sea.
2002.10 – : The deep circualtion of the Japan Sea.
1997.02 – : Development of heavy oil spill behavior forecasting model
1996.04 – 2002.03: Research on formulation of water mass in the Japan Sea
Q What about satellite data makes it essential to understanding what is occurring in the marine environment?
Q My work involves comprehending the ocean cycles and making forecasts. For this I use data including sea-surface altitude, water temperature and wind direction. Satellite data is indispensable to my research as it forms the basis for resetting the initial conditions for predictive models. On-site measurements are difficult to immediately reflect in models, while, satellite data offers something closer to real time. This makes it possible to comprehend the surface current for a large area using sea-surface altitude data, which is essential in constructing predictive models.
In addition, satellite surface altitude data is used to check the results of marine cycle models and under the Argo Project, nearly 3,000 profiling floats have been released into the world’s oceans. Floating on the surface, these regularly monitor the salinity and vertical profile of the water temperature. This data is gathered via satellite.

Q Currently, what kind of research are you carrying out?
Q I am conducting research on the oceanic circulation of the Pacific Ocean and Japan Sea. In regard to the latter, I am using satellite data to put together a short-term prediction methodology for up to five days in the future and a long-term version for up to two months in the future. In research on the Tsushima Current, cruise ships that regularly travel through the area are used to monitor current velocity, surface temperature, salinity and chlorophyll. In addition, models have been constructed that predict the advection and diffusion for heavy oil drifts and these have been confirmed largely accurate via on-site monitoring of actual heavy oil drifts.
Monitoring of the Japan Sea has also been conducted using profiling floats.

Q What requests do you have or what would you like to see happen regarding satellite data??
Q Currently, satellite data is being used for two-month oceanic circulation forecasts. I am inputting tidal information for the five-day forecast. The tidal data has a large impact on coastal areas. Due to conditions having to do with the time resolution the TPEX/ERS sea-surface altitude is supplied at around an interval of every 10 or 30 days so it is not possible to incorporate this into short-term forecasts. If the time resolution of information improves, then I think we can expect to see it used in short-term forecasts.

Q What research interests you right now?
Q I would like to gain an understanding of the effects that global warming will have on the Sea of Japan. In the Japan Sea, up until about 50 years ago, there was a convection current that flowed deep in the ocean. However over the past 50 years, this has almost entirely disappeared and I think that this may be an early impact and indication of global warming. I would like to investigate this and make a model based on the structural changes that the past 50 years has brought to the Japan Sea – known as the Mini Pacific Ocean. This model could then be used to forecast future changes. Ultimately, we would like to expect that this will segue into a means of predicting change to the marine environment on a global scale. The ocean’s vertical circulation, both from a marine life and a thermal circulation perspective, is very important. When the vertical circulation ceases, this has the potential to cause drastic changes in climate. The climate is intimately related to the ocean’s vertical circulation and I believe that vertical circulation data will provide a hint that aids in the forecasting of climate change.
I am trying to boost the level of accuracy in other circulation models. As a result, we have become able to reproduce on a small scale, the structure of the occurrence of the Karman Vortex that takes place in the wintertime in the western channel of the Tsushima Current. Also, it is well known that a counter-clockwise current has been observed in deep in the Japan Sea, and while conventional models were not able to reproduce this, however by heightening the precision of the circulation model we were able to recreate this phenomenon. I believe that satellite data can be used to compare these circulation patterns that typically appear.
In the future, I would like to target the East Asian seas, putting together a model fusing the Japan Sea, Yellow Sea and East China Sea, which, for instance, could be used to show the change in fresh water currents due to the construction on the Three Gorges Dam. Freshwater is important biologically and from a physics viewpoint as layers of the ocean with more freshwater are lighter and likely have an impact on circulation.

Q What are some issues related to use of satellite data?
Q When comparing the monitoring results of buoys and satellite data, I think that it is apparent that the frequency of data sampling needs to be increased. Also, TOPEX’s sea-surface altitude measurements, due to a low level of accuracy in regard to the geoid, tend to have large margins of error. Currently, I am using information about the amount of fluctuation of the sea-surface altitude. I think that issues regarding the basic principles of this remain to be resolved. Nonetheless, as it allows for the gathering of information for a broad area, satellite data is essential for marine monitoring.
( Interview date: April 10, 2005 )