A study on the validity of buoy mounted Acoustic Doppler profilers: A comparison of upward and downward looking systems in Onslow Bay, NC

The National Data Buoy Center (NDBC) maintains an extensive array of moored buoys around the world. Hence, mounting Acoustic Doppler Current Profilers (ADCPs) to these buoys has proven to be an avenue worth exploring. In a previous study done by Seim and Edwards [1], a downward-looking ADCP from NDBC buoy 41008 was compared to an upward-looking ADCP from the University of North Carolina at Chapel Hill (UNC) located in close proximity to test the validity of ADCP measurements made by a buoy-mounted ADCP. Since configurations of the systems were not standard, the two did not agree well. Since this time, NDBC has made several changes to the configuration of their ADCPs. This study is to again compare a NDBC downward-looking ADCP mounted to buoy 41036 to an upward-looking ADCP from the University of North Carolina at Wilmington (UNCW) mounted on the seafloor to test the reliability of NDBCs present buoy-mounted ADCP configuration. Both of these systems are located on the shallow continental shelf of Onslow Bay, North Carolina. An 18-day time series was obtained from each ADCP. Preliminary results show good agreement between the two systems. In light of the fact that the buoy-mounted system is subjected to movement by atmospheric and oceanic processes, further data conditioning is investigated to see if more precise environmental thresholds, specifically wave height thresholds, can be put in place for more accurate current measurements.