The Status of Data Produced by NDBO Wave Data Analyzer (WDA) Systems

The Data Buoy Office of the National Oceanic and Atmospheric Administration (NOAA) operates a number of buoys in the continental shelf and deep ocean areas near the United States. Data buoys with Wave Data Analyzer (WDA) systems are providing wave energy spectra and significant wave heights on an operational basis. The NOAA Data Buoy Office (NDBO) has developed a modified Waverider buoy, designated WRANSAC (Waverider Analyzer Satellite Communicator), as a measurement standard for at-sea calibration of buoys with WDA systems. Calculation of wave energy spectra from WDA-equipped buoys requires knowledge of a noise correction function and a power transfer function for the entire wave measurement system, including the buoy hull and mooring. Examples of these functions are provided herein and potential error sources are examined. NDBO´s present noise correction function modifies wave energy spectra at low frequencies, but has a small overall effect on spectra and significant wave heights. Hull transfer functions for two operational data buoys have been determined by calibrations, but additional calibrations are needed for other buoys, and also to provide better estimates of the hull transfer functions and the noise correction function. Based on these calibrations, approximate accuracies and confidence intervals for WDA-measured wave energy spectra and significant wave heights can be determined.