Numerical modelling of drifting buoys and its relevance to Lagrangian tracking

In the past decade, the NOAA Data Buoy Office (NDBO) has utilized spar-type drifting buoys to collect a wide range of climatological information in data sparse ocean regions. One of the ancillary uses of these drifting buoys has been to serve as Lagrangian measurement devices of ocean currents. Drifting buoy systems are designed at NDBO using a numerical model computer program to predict buoy motions and forces in simulated environments. This program has been validated through wave tank model tests and has been demonstrated in practice to be an effective means for providing qualitative information for selecting the optimum buoy system parameters. A brief description of the numerical model and its function in the design process is given in this paper. In addition, four specific aspects of the Lagrangian current measurement problem are identified for which the model can provide valuable input. Finally, a plan is outlined for the rational development of improved Lagrangian tracking buoy systems, using a combination of numerical techniques and model testing.