This data set contains profiles collected with an LADCP system during the cruise EN586 in summer 2016. The profiles contain information on all three components of the oceanic velocity field, as well as on acoustic backscatter.
Andreas Thurnherr. 2017. Lowered Acoustic Doppler Profiler Data (LADCP), Endeavor (EN586), Gulf of Mexico, July 24 to August 14, 2016. Distributed by: Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC), Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7K072BN
The data were collected to yield information on ocean dynamics (currents, internal waves, and turbulence).
Data Parameters and Units:
This data set contains both processed profiles and the raw data required to re-process the profiles if needed. As a result, there are several different types of files: 1) Original ADCP Raw Data. Two files per profile, one from each of the two ADCPs (uplooker and downlooker). Format: TRDI PD0 format (manufacturer-specific binary format). These files can be used for processing. 2) Corrected ADCP Raw Data. ADCP raw data with merged pitch, roll and heading from external sensors. Two files per profile, one from each of the two ADCPs (uplooker and downlooker). Format: Teledyne/RDI (TRDI) PD0 format (manufacturer-specific binary format). These files should preferentially be used for processing. 3) Time-series files with 24-Hz CTD and GPS data. One file per profile. Format: Seabird Electronics (SBE) cnv format (manufacturer-specific ASCII format). These files are used for processing. Latitude (decimal degrees), Longitude (decimal degrees), Ship, Cruise, Station, ITS (90), Conductivity (S/m), Sampling frequency, Start time (UTC) 4) Processing parameters. One file each for horizontal velocity (Matlab file set_cast_params.m) and vertical velocity (perl script ProcessingParams.default). 5) Horizontal-velocity profiles. One file per profile. Format: netCDF with the following fields: i) Depth in meters. ii) Zonal velocity (u) in m/s. iii) Meridional velocity (iv) in m/s. iv) Formal velocity-magnitude uncertainty in m/s. 6) Vertical-velocity profiles. One file per profile. Format: netCDF with the following fields: i) Depth in meters. ii) Downcast vertical velocity. iii) Upcast vertical velocity.
Horizontal velocity profiles were created with the LDEO implementation of the velocity-inversion method (Visbeck, 2002). Vertical velocity profiles were created with the method of Thurnherr (2011). Current versions of both processing packages are available from http://www.ldeo.columbia.edu/LADCP.
All profiles were collected with Teledyne RDI 300kHz and 600kHz Workhorse ADCPs.
Data quality of the horizontal velocities was assessed by comparing the LADCP velocities in the upper ocean with the corresponding SADCP velocities. Based on this assessment, most of the profiles are of very high quality with expected errors of ~3cm/s in the individual velocity components (Thurnherr, 2010). Based on a comparison between independent vertical-velocity profiles from the two ADCPs (in the final profiles the data are combined) many of the profiles, in particular the upcast profiles, are associated with measurement artifacts related to large instrument tilts. Assessment is hampered by generally very low signal levels.