SWIFT data collected in the Southern California Bight by SWIFT drifters as part of the ONR Langmuir Circulation Departmental Research Initiative (LC-DRI)
Data files
Mar 06, 2023 version files 4.47 GB
-
LCDRI_SIG-BurstData.zip.zip
4.47 GB
-
README.md
1.92 KB
Jun 11, 2024 version files 4.49 GB
Abstract
This is the public archive for ADCP data collected with SWIFT drifters and Mixed-Layer Floats during the 'Langmuir Circulation' Office of Naval Research Departmental Research Initiative (LC-DRI) field experiment, conducted between March 19th and April 6th, 2017 in the Southern California Bight 40 km west of Catalina Island. The floats and drifters were deployed and recovered from the R/V R.G. Sproul during cruise SP1709 (Cruise DOI: 10.7284/907464). SWIFTs were deployed during storms with wind speeds up to 20 m/s and sampled strong diurnal warm layers during weaker wind periods.
README: SWIFT Data collected in the Southern California Bight by SWIFT drifters as part of the ONR Langmuir Circulation Departmental Research Initiative (LC-DRI)
The data contained in this archive are quality controlled SWIFT data and MLF data, as well as raw high-resolution velocity data collected with SWIFT drifters (Thomson et. al. 2012) in the Southern California Bight in March and April of 2017.
Description of the processed SWIFT and MFL data and file structure
Two structures, 'swift', and 'mlf' are contained in LCDRI_dryad.mat. These data structures contain substructures (fields) with the processed data collected by individual instruments. Substructures are named by their serial number and the date the data collection began. For example, 'swift.SN250404' contains data collected by SWIFT 25, beginning April 04.
SWIFT Structure Variables
time: time (matlab datetime)
lon: longitude (degrees N)
lat: latitude (degrees E)
driftspd: drift speed (m/s)
driftu: drift zonal velocity (m/s)
driftv: drift meridional velocity (m/s)
tair: 1 m air temperature (deg C)
tsea: sea surface temperature (deg C)
depth: depth of velocity bins (m)
subu: zonal velocity (m/s)
subv: meridional velocity (m/s)
wavefreq: frequencies of wave power spectra (Hz)
wavepower: wave energy per frequency (m^2/Hz)
waveustokes: stokes drift from measured peak wave period and significant wave height (m/s)
wavesigH: significant wave height (m)
wavepeakT: energy weighted peak wave period (s)
wavepeakdir: peak wave direction (deg from N)
windu: 1 m wind speed (m/s)
windfreq: frequencies of wind power spectra (Hz)
windpower: wind energy per frequency (m^2/Hz)
surfz: depth of dissipation bins (m)
surftke: surface dissipation (m^2/s^3)
MLF Structure Variables
time: time (matlab datetime)
depth: depth bins (m)
lon: longitude (degrees N)
lat: latitude (degrees E)
temp: temperature (deg C)
sig: density (kgm^(-3))
sal: salinity (psu)
Description of the raw ADCP data and file structure
Data files are named using the serial number of the SWIFT, followed by the time at the start of the ADCP burst.
Each file contains data from a single 8-minute ADCP burst, contained in two Matlab structures: 'avg' and 'burst', which contain data from the four slanted broadband beams and the single high-resolution pulse-coherent central beam, respectively. Note: there is also an empty 'echo' structure, which is filled only when the ADCP is operating in echo mode. The HR 'burst' data are of primary interest for turbulence calculation. The fieldnames within the burst structure are as follows:
time: datetime stamp for each ADCP ping.
Temperature: temperature measured by the CTD (deg C)
Presssure: pressure at the ADCP (deg)
Heading: heading of the ADCP (deg)
Pitch: pitch of the ADCP (deg)
Roll: roll of the ADCP (deg)
CellSize: separation between vertical bins (m)
Blanking: distance from transducer to first bin (m)
VelocityData: along-beam velocity values for the four broadband beams (ms^{-1})
AmplitudeData: acoustic backscatter amplitude (counts)
CorrelationData: pulse-pair correlation (%)
Fieldnames in the 'avg' structure are the same.
Sharing/Access information
N/A
Code/Software
SWIFT codes for processing SWIFT-mounted Signature 1000 burst data can be found here: https://github.com/SASlabgroup/SWIFT-codes/tree/master/Signature
Methods
SWIFT drifters were deployed at the ocean surface and collected measurements of near-surface velocity in a surface following reference frame using high-resolution acoustic Doppler current profilers (ADCPs), Nortek Signature 1000s. Mixed-layer Floats control their bouyancy to profile vertically in the ocean, and measured conductivity, temperature and density measurements. Also contained in this file are raw ADCP data -- subject to minimal quality control onboard the SWIFTs, but are otherwise unprocessed other than conversion from binary. This 'raw' data is available for turbulence estimates. The .zip file contains .mat files with data and a READ ME (.txt file) describing the data format. Processing codes for the SWIFT-mounted Signature 1000s can be found here: https://github.com/SASlabgroup/SWIFT-codes/tree/master/Signature.
Usage notes
Matlab is required to open the data files (.mat files) included in this archive.