If something falls into the vast ocean, where should you look for it? Lin Fangyu, director of Walrus Development Technology of the Central Meteorological Administration's Walrus and Climate Group, pointed out that the Meteorological Administration has established a three-dimensional ocean current operational forecast model that can not only predict sea surface currents, but also calculate currents at different depths such as 10 meters and 20 meters underwater. In the past, when an Air Force aircraft crashed into the sea, the ocean current model was used to estimate the possible drift position. When a ship has an oil spill, it can also simulate where the oil pollution may drift, providing a reference for search and rescue and disaster prevention.
The Meteorological Department held a practical meteorological workshop. Lin Fangru explained ocean current model forecasting and practical applications. She said that the Meteorological Administration has built a three-dimensional ocean current operational forecasting system using the SCHISM numerical model, using the U.S. ocean current model as boundary conditions and inputting the Meteorological Administration's meteorological fields. It can conduct ocean current forecasts for the next four days. In addition to surface currents, it can also calculate three-dimensional ocean currents and sea temperatures at different water depths.
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In order to grasp Taiwan's complex coast and port topography, the ocean current model adopts a triangular grid. The offshore grid is larger than 8 kilometers, and the offshore grid can be reduced to about 200 to 500 meters. The port area will be further densely populated; the vertical direction is layered according to the water depth. There may be only 5 layers in shallower areas and more than 48 layers in deeper areas.
However, ocean currents "eat" computer resources quite a bit. Lin Fangru said that the wave model can be calculated four times a day, but the current model can only be calculated once a day due to the large number of grids, which takes up a lot of computing resources on the Meteorological Administration's supercomputer.
Another difficulty in ocean current forecasting is the lack of sea observation data. Lin Fangru said that there are a large number of observation stations on land for meteorological model verification, but the vast ocean lacks observation data of the same density, so we can only collect domestic and foreign drifting buoys and other data as much as possible for verification. Maritime data buoys cost millions of dollars each and are difficult to deploy and maintain. They may also be entangled in fishing nets or collided with ships.
Lin Fangru also took the "Qimei Buoy Adventure" as an example. The buoy deployed by the Meteorological Administration near Qimei once drifted at sea, drifted for a while, stopped, and then continued to drift. The Meteorological Administration installed positioning equipment to track it and finally recovered it, highlighting the difficulty of maintaining maritime observation equipment.
Lin Fangru also cited the "Angel Ship" incident off Kaohsiung as an example. At that time, the ship ran aground and was hit by an approaching typhoon. The Meteorological Administration was worried that oil leakage from the ship would pollute the southwest coast, so it launched an oil spill simulation and used a numerical model to predict the possible drift direction of the oil pollution, and continued to provide relevant units as a response reference. Ocean current pattern information is also integrated into marine and meteorological services such as blue highways, bathing beaches and surfing spots to provide public reference.
