Shipboard ADCP

	View Data
	To assist in the interpretation of the data, it can be displayed using the Hawaii Ocean Time-series Data Organization & Graphical System (HOT-DOGS©).

Sampling Procedure

Currents in the upper ocean (0-1200 m) during 2021 were measured using shipboard Acoustic Doppler Current Profilers (ADCP) on board R/V Kilo Moana.

Onboard ADCP data are collected and preliminarily processed in real-time using the University of Hawaii's CODAS processing system. This system allows for automatic data quality control and real-time graphic display of current profiles and other data products while at sea. Should any ancillary data stream be disrupted at sea or found to be in error, raw data are saved and a complete data re-processing is possible later.

The R/V Kilo Moana is equipped with two ADCP systems. A Teledyne RD Instruments Ocean Surveyor 38 is located on the ship's starboard side, and an RD Instruments WorkHorse 300 is located on the port side; both feature a transducer depth of 7 m. The Ocean Surveyor operates at 38 kHz and can profile to 1200 m in broadband mode (OS38BB) with a bin size of 12 m averaging ensembles every 5 minutes. In narrowband mode (OS38NB) with 24 m bins, profiles can reach as deep as 1500 m. The WorkHorse (WH300) operates at 300 kHz, typically profiling to a maximum of 100 m with a bin size of 2 m and averaging ensembles every 2 minutes. Heading information is taken from the gyrocompass and corrected using a TSS POS/MV 320 (an integrated inertial and GPS). An Ashtech ADU5 is used as a heading-correction device should there be a problem with the POS/MV. The POS/MV system provides position data with an Ashtech ADU5 and a Trimble GPS as backups.

The final processing of shipboard ADCP data involves applying small heading corrections to the velocity data based on water track calibrations, trimming unnecessary data from the beginning and ends of the cruise, followed by visual inspection of the final dataset with manual data flagging of suspicious points.

For all the HOT cruises conducted in 2021, ADCP data were collected using three instruments, OS38BB, OS38NB, and WH300. However, during the HOT-326 expedition, the OS38 instrument exhibited some issues with the collected data. As a result, only the WH300 was used.

Results

An overview of the shipboard ADCP data is given by the plots of velocity as a function of time and depth while on station (below-left) and velocity as a function of latitude and depth during transit to and from Station ALOHA and Station Kaena, combined (below-right). As in previous years, currents were highly variable from cruise to cruise and within each cruise.