岸基高頻雷達(CODAR)海流資料同化方案與運用

The main objective of this project is the development of schemes for assimilation of observed surface ocean currents into a hydrodynamic model for seas around Taiwan. The observed near-surface (~1m) ocean currents are derived from High-Frequency radars (Coastal Ocean Dynamics Applications Radar, CODAR). The proposed data assimilation scheme for the two-dimension surface currents is based on the Physical-space Statistical Analysis System (PSAS), which operates directly in physical space. Preliminary twin experiments show that a known ocean state can be reproduced by the data assimilation scheme of the PSAS. In addition to the scheme that only assimilates surface current data into the surface layer of the model, alternative schemes are under construction for projecting surface information into subsurface layers. These data assimilation schemes are mainly based on dynamical inference methods. The CODAR-derived current data assimilation technique is based on the application of a pseudo-shearing stress over the surface layer of the model. This pseudo-shearing stress depends on the differences between the model-predicted velocities and the velocities observed by the CODAR. The statistical validation of the data assimilation schemes will be tested in this project. The assimilation results will be compared with available in-situ hydrographic data and limited subsurface mooring measurements.