Using a 1200 kHz workhorse ADCP with mode 12 to measure near bottom mean currents

Using high frequency acoustic Doppler current (ADCP) profiling technology, it is possible to make high-resolution measurements of mean current profiles within a few meters of the seabed. In coastal applications, mean current speeds may be 10 cm/s or less, and oscillatory wave currents may exceed 100 cm/s during storm events. To resolve mean flows of 10 cm/s or less under these conditions, accuracies of 1 cm/s or better are desirable. RD Instruments (RDI) has recently added a fast ping mode (mode 12) to their ADCP sampling schemes which may make it possible to achieve 1 cm/s to over 100 cm/s dynamic range with their 1200 kHz ADCP during a 4-month deployment using three standard battery packs. Mode 12 combines fast ping rates with high spatial resolution and high maximum velocities. Mode 12 may be more suitable for these types of high resolution, high velocity measurements than RDI's existing shallow water modes (5 and 8).