| Budget Amount *help |
¥4,000,000 (Direct Cost: ¥4,000,000)
Fiscal Year 2003: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2002: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2001: ¥3,000,000 (Direct Cost: ¥3,000,000)
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| Research Abstract |
It is well known that CO_2 content of the atmosphere is increasing. The source of this increasing CO_2 has been assumed to be the combustion of fossil fuels and land use change, and the ocean has been considered as a major sink for anthropogenically produced CO_2. This implies that the accurate measurement of CO_2 exchange rates across the air-sea interface is the key to achieving a deeper understanding of the CO_2-global climate dynamics. The most promising technique for turbulent flux measurements is the eddy correlation technique. However, the difficulties of the eddy correlation measurements on research vessels or buoys are well recognized. The CO_2 flux across the air-sea interface is usually estimated by the bulk technique when the measuring platform is a research vessel. CO_2 fluxes by the bulk technique, however, are affected by many factors such as water temperature, salinity and bio-productivity in the seawater, and wind speed and stability conditions in the atmosphere. Many
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of the unknown parameters mentioned above are subsumed within the transfer coefficient, because the bulk technique is the primitive one which involves the calculation of COQ fluxes from three parameters, the partial pressure of CO_2 in the atmosphere and in the seawater, and the bulk transfer velocity. We planned the project to investigate meteorological techniques such as aerodynamic, spectral density, and eddy correlation techniques to measure, CO_2 fluxes over the ocean. For this purpose, observations were curried out during the summer season since 2000 on a well-designed pier of the Ogata Wave Observatory, Kyoto University in the Sea of Japan. Turbulent fluxes determined by the eddy correlation, aerodynamic and spectral density techniques agree well under sea breeze conditions. The aerodynamic and spectral density techniques do not require explicit measurements of vertical wind velocity. This is the essential feature of the flux measurement technique as regards its use with data obtained on research vessels or buoys. This also encourages us to conclude that the aerodynamic and spectral density techniques are suitable to be used in place of the bulk technique. Less
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