Time-series measurements of oceanographic and seabed response data collected in Cape Cod Bay, Barnstable, MA, March 10 to April 7, 2021

A quadpod mounted with upward- and downward-looking Nortek Signatures, two Nortek Vectors, a Seabird MicroCAT, a Seabird Seagauge, an Imagenex Sonar, an Aquatec Aquascat, and two Edgetech releases was loaded onto the R/V Tioga in Woods Hole, Massachusetts. The ship sailed to Cape Cod Bay, where a seabed bathymetry transect from inshore to offshore was conducted and grab samples of the seabed were collected to find an appropriate deployment site. The quadpod was lowered into the water and the latitude and longitude were recorded. The releases were pinged and a signal was received back indicating the quadpod was upright. Steven Suttles is the contact for this process step and subsequent process steps until otherwise noted.

The R/V Tioga sailed from Woods Hole, Massachusetts to Cape Cod Bay. The releases were pinged and a signal was received back indicating the quadpod was upright. The release command was initiated and the quadpod was hooked and raised onto the deck. All instruments were clean and free of biofouling. Before departing the site 3 grab samples of the seabed were collected for grain size analysis. All data were downloaded from the instruments.

The raw data files from each sensor were processed and converted to netCDF using the stglib Python library, a package of code to process data consistent with procedures of the USGS Coastal/Marine Hazards and Resources Program; see "history" global attribute in each processed netCDF file for stglib and python versions used. In stglib, attributes conforming to Climate and Forecast (CF) Conventions were added; see "Conventions" global attribute in processed netCDF files for CF version used. All times are in Coordinated Universal Time (UTC). For all pressure sensors, corrected pressure data (P_1ac) were calculated by finding an offset with local atmospheric pressure readings when the pressure sensor was reading in air just prior to deployment. Pressure data were corrected using the offset and a time-series of local atmospheric pressure over the course of the deployment to remove the atmospheric contribution to the deployed pressure data. The resulting corrected pressure variable is the pressure due to seawater (standard_name "sea_water_pressure_due_to_seawater" in netCDF files). Data quality assurance and quality control (QAQC) was performed by inspecting all variables and replacing spurious values with the fill value; see global attribute ‘VAR_Fill’ in netCDF files for fill value. Details of which portions of data were flagged and replaced are available in the metadata in each netCDF file and information about the individual QAQC trimming functions are available in the stglib documentation (https://stglib.readthedocs.io/en/latest/) in the "Instrument configuration file" section.The root of the netCDF files are named using the convention ####XZZZ where '####' is the mooring number, 'X' is the position on the mooring of the sensor with 1 being closest to the surface, and 'ZZZ' (length between 2 and 5 characters) is an abbreviation for the instrument that was deployed; see instrument abbreviations table in stglib documentation https://cmgp.code-pages.usgs.gov/stglib/insttbl.html. After instrument abbreviation there are additional processed file suffixes that identify the type and level of processing; '-a' is Best Basic Version (BBV = highest level of processing), 'b' is burst or continuous fast sample rate data, 's' is wave statistics from built-in stglib, 's_diwasp' is wave statistics from pyDIWASP library, and 't' is tide data. For example, in the file 11263mc-a.nc, '1126' is the mooring number, '3' is the position of the sensor on the mooring, 'mc' refers to the Seabird MicroCAT sensor, and '-a' indicates it is BBV.

More QAQC was required for the near-bed velocity measurements from the downward pointed Nortek Signature in 5-beam High Resolution (HR) mode and the two Nortek Vectors which were affected by periods of low correlation and high signal noise that were likely due to low amounts of acoustic scatters in the water at these times. The Vectors and the HR mode for the Signature use a pulse-coherent ping pair for the velocity measurements that is more impacted by low scattering conditions, and as a result the earth coordinate velocities of u_1205, v_1206, w_1204, and w2_1204 (Signature only) were filtered using a 4th order Butterworth lowpass filter with a 2 second cutoff to smooth out the noise. The unfiltered velocities were preserved in the netCDF files by copying them to a new variable with "_unfiltered" appended to the original variable name prior to applying the filter. The downward looking Signature in 5-beam HR mode required additional QAQC because of the limited velocity range in the 5-beam HR mode that was exceeded during times of large waves and high orbital wave velocities causing phase wrapping of the measured velocities. Times of affected velocity measurements were identified using minimum correlation and point-point maximum absolute difference thresholds to fill bad values with the fill value (NaN).

There was a typo in the first online link to the DOI, so this was fixed. (20251117)