DOI: 10.5061/dryad.hx3ffbgk0
title: Measurements of nearshore waves through coherent arrays of free-drifting wave buoys

description: Surface gravity wave breaking occurs along coastlines in complex spatial
 and temporal patterns that significantly impact erosion, scalar transport,
 and flooding. Numerical models are used to predict these processes, but
 many models lack sufficient evaluation with observations during storm
 events. To fill the need for more nearshore wave measurements during
 extreme conditions, we deployed coherent arrays of small-scale,
 free-drifting wave buoys named microSWIFTs. The result is a large dataset
 covering a range of conditions. The microSWIFT is a small wave buoy with a
 GPS module, and Inertial Measurement Unit (IMU) used to directly measure
 the buoy's global position, horizontal velocities, rotation rates,
 accelerations, and heading. We use an Attitude and Heading Reference
 System (AHRS), 9 degrees-of-freedom Kalman filter to rotate the measured
 accelerations from the reference frame of the buoy to the Earth reference
 frame. We then use the corrected accelerations to compute the vertical
 velocity and sea surface elevation. The measurements were collected over a
 27-day field experiment in October 2021 at the US Army Corps of Engineers
 Field Research Facility in Duck, NC. The microSWIFTs were deployed as a
 series of coherent arrays. They all sampled simultaneously with a common
 time reference, leading to a robust spatial and temporal dataset during
 each deployment. We evaluate wave spectral energy density estimates from
 individual microSWIFTs by comparing them with a nearby acoustic waves and
 currents (AWAC) sensor. We also compare significant wave height estimates
 from the coherent arrays with the nearby AWAC estimates. A zero crossing
 algorithm is applied to each buoy time series of sea surface elevation to
 extract realizations of measured surface gravity waves, yielding 116,307
 wave realizations throughout the experiment. These measurements spanned
 offshore significant wave heights ranging from 0.5 meters to 3 meters and
 peak wave periods ranging from 5 to 15 seconds over the entire
 experiment. 
description: This dataset was collected as a part of a larger collaborative
 effort called DUNEX (During Nearshore Events Experiment), funded through
 the US Coasal Research Project. The dataset was collected using small wave
 buoys named microSWIFTs developed as a part of the project. The data was
 collected from October 3–October 30th of, 2021, at the US Army Corps of
 Engineers Field Research Facility in Duck, North Carolina, USA. The
 microSWIFTs were deployed in large arrays ranging from 2–50 simultaneously
 deployed buoys. Each deployment is referred to as a "mission,"
 and all data from each buoy is stored in a netCDF file associated with
 each mission. The buoys are equipped with a GPS receiver and an inertial
 measurement unit (IMU). They measure their position, accelerations,
 rotation rates, and heading as they drift through the surf zone. The
 accelerations are despiked and corrected from the buoy reference frame to
 the Earth reference frame using a 9-degree-of-freedom indirect Kalman
 filter. The corrected accelerations are then integrated into velocities
 and positions. Further details on these processing methods are written in
 the manuscript that will be submitted to the Earth System Science Data
 journal. All code for processing is also publicly available at https://github.com/SASlabgroup/DUNEXMainExp.
description: All the data is saved in netCDF file formats that include all
 associated metadata with the files. The data can be read into any major
 programming language and multiple graphic user interfaces can also
 interface with the data. Common programming languages that can use this
 data are Python and MATLAB. Examples of using the data with Python can be
 found at https://github.com/SASlabgroup/DUNEXMainExp.