Performance and verification of the oil spill modeling system
for the Sea of Japan
Sergey VARLAMOV 1) and Jong-Hwan YOON2)
1)
Institute of Environmental Sciences, RISSHO University,
1700 Magechi, Kumagaya city, Saitama 360-0194, JAPAN
e-mail: varlamov@ris.ac.jp
2)
Research Institute for Applied Mechanics, Kyushu University,
6-1 Kasuga-koen, Kasuga city, Fukuoka 816-8580, JAPAN
Oil spill fate and drift prediction system is one of practical applications for high performance
state-of-the-art atmospheric and ocean circulation models. The oil spill physical properties and drift
model is also an important part of this system. The version of the oil spill analysis and prediction
system was developed by authors and adopted for the Sea of Japan. Examples of applications for
modeling of the Nakhodka oil spill in the Sea of Japan that took place January 1997 were reported at
the last 2nd Workshop on Next Generation Climate Models in Toulouse, 2000 (Varlamov et. al., 1999,
2000). During past year the serious modifications of the spill model as well as of the ocean circulation
subsystem were done. System is oriented on the operational forecast of accidental oil spills and
includes the meteorological data processing subsystem, ocean currents simulation models, oil spill
simulation model and the software for results graphical presentation and analysis. The spill model is
based on the particles tracking method and the last version includes the simulation of the oil physical
properties that changes the modeled oil droplet characteristics during the spill evolution (density, size,
viscosity and water content in the oil emulsion). Oil spill prediction system structure is presented and
shortly discussed. The meteorological subsystem utilizes the production of the JMA official regional
atmospheric prediction system. The ocean circulation model is a part of the system and both the 3D
and 2.5D versions were tested. The combination of local wind drift model with the barotropic model
of the Japan Sea (2.5D model) is implemented in to the operational version of system (Varlamov et.
al., 2000).
April 3, 1997 in the Sea of Japan one more oil spill accident happened, although not so
dramatic as that caused by the tanker Nakhodka oil spill. Korean tanker O-Sung No 3 was ruptured in
the Tsushima Strait close to the Korean coast and about 229 kiloliters of the heavy Bunker C oil were
spilled. Largest part of oil was recovered from the sea by joint Korean and Japanese actions, however
the pollution of the Tsushima Island shoreline was reported.
Strong tidal and residual currents characterize the Tsushima Strait area. The ability of the
ocean circulation model to reproduce correctly both these components was carefully checked. At the
open boundaries at the outer area of the Tsushima Strait the 2.6 Sv mean inflow current was applied
and the sea level anomalies relative to the long-term mean values were forced by 16 tidal harmonics.
The simulated volume transport through the Western channel of the Tsushima strait was about 1.5
times larger from this value for the Eastern channel. The sea level simulation compared with
observations for Hakata and Idzuhara tidal stations also gave good comparison: root mean square
errors for hourly values were 12 and 9 cm correspondingly compared with observed root mean square
sea level variability 46 cm for Hakata and 45 cm for Idzuhara stations.
At the outflow open boundaries the free gravitational wave conditions were adopted, although
the tidal variations could be also applied. Normal sea current anomalies in tidal-forced open boundary
points were adapted from internal points with fixed Newton type adaptation parameter. It avoided the
possible instability generation in boundary regions.
The O-sung spill simulation demonstrated good comparison of simulated oil spreading with
observed one. At the initial stage the wind drift of surface slicks was most important and slick drifted
against the mean sea current. About April 6 the highest concentration oil patches changed the drift
direction. Fig. 1 demonstrates the position of modeled oil particles and relative oil concentration for
the upper 2 m layer. By rectangle the observed position of oil patches for this time is marked. Large
difference between the particle’s positions and the concentration field is produced owing to the
different size of used particles: largest droplets that drift at the sea surface form the area of highest oil
concentration.
System code parallelization and related increase of the system performance will be discussed.
Fig.1 Position of modeled oil particles (left) and relative oil concentration (right) in upper 2 m April 7,
1997. Initial accident point near 34 36N, 128 35E is marked by small circle.
References
1. Varlamov S.M., J.-H. Yoon, N. Hirose, H. Kawamura and K.Shiohara, Simulation of the oil spill
processes in the Sea of Japan Sea with regional ocean circulation model. Journal of Marine
Science and Technology, 1999, 4 (3), pp. 94-107.
2. Varlamov S.M., J.-H. Yoon, H. Nagaishi & K. Abe, Japan Sea oil spill analysis and quick response
system with adaptation of shallow water ocean circulation model. Reports of Research
Institute for Applied Mechanics, Kyushu University, 2000, No. 118, pp. 9-22.