Ocean currents from lowered acoustic Doppler current profilers (LADCP) of the cDrake Experiment in the Drake Passage with annual cruises of the RVIB Nathaniel B. Palmer from 2007 to 2011 assembled at the Scripps Institution of Oceanography

Using the conventional "shear method" for processing (Fischer and Visbeck, 1993), overlapping profiles of vertical shear of horizontal velocity are averaged and gridded, to form a full-depth shear profile. The shear profile is integrated vertically to obtain the baroclinic velocity (velocity profile with zero depth-averaged mean value); the unknown integration constant is the depth-averaged or barotropic velocity. This barotropic component is computed as the sum of the time-averaged, measured velocity and the ship drift (minus a small correction, less than 1 cm/s, to account for a nonconstant fall rate).

A newer method ("inverse method") improves the calculation by adding additional constraints, such as shipboard ADCP (SADCP) and bottom tracking, to solve for the velocity profile using a linear least squares inverse technique (Visbeck, 2002). Lowered ADCP data makes use of ancillary information to produce the processed data product. The ancillary datasets include CTD data (used to estimate speed of sound, depth, vertical velocity), GPS (used to estimate ship drift), magnetic declination (for ADCP magnetic compass correction), and shipboard ADCP (added as a constraint for the inverse method).

Data files for the processed set are in ASCII text and NetCDF. Raw data are given in a variety of formats, some proprietary binary files, and made available in case a user prefers to reprocess the set from “level-0” status.