Surface Wave Instrument Float with Tracking (SWIFT)  data

Data products are ensembles from 512-second "bursts" of raw data, at intervals of 720 seconds.  These are combined in a single structure in Matlab, which is actually an array individual structures, with data products for each burst.  Use square brackets to index all burst ensembles, i.e.: 

	>> plot([SWIFT.time],[SWIFT.sigwaveheight],'x')

The SWIFT code library is at https://github.com/jthomson-apluw/SWIFT-codes


Level 0 (L0) data are raw data in burst files of 512 seconds at intervals of 720 seconds.  The data are stored separately for each sensor payload type (and serial com port), in a directory structure by day and a file-naming convention using hour and burst number.  

Level 1 (L1) data are results for each burst (typically 5 per hour) using on-board processing of the raw data to determine data products such as wave spectra, turbulent dissipation rates, bulk winds, etc.   These are available via Iridium telemetry during and after a deployment.  Quality control is limited.  

Level 2 (L2) products have been through post-processing of the raw data, and have significantly more quality control. In some cases, the L2 data have been re-processed for higher temporal resolution than the standard 720 s interval.   These are denoted with a "dt" giving the time step (e.g., L2_dt10s is an L2 product every 10 s).  Some products, such as wave spectra, are only produced for the standard 720 s interval, because anything shorter than this does not have sufficient raw data.   


The SWIFT structures only contain fields of the payloads that were on that particular SWIFT.  The full list and units follow, but note that no single SWIFT would have all of these fields:  

SWIFT.ID: hull number of the buoy 

SWIFT.uplooking.tkedissipationrate: vertical profiles of turbulent dissipation rate in W/kg (= m^2 / s^3) from an uploading AquadoppHR

SWIFT.uplooking.z: depth bins, in meters below the wave-following surface, for the TKE dissipation rate profiles

SWIFT.downlooking.velocityprofile: vertical profiles of horizontal velocity magnitude, in m/s, relative to the float (not corrected for drift) from an downlooking Aquadopp

SWIFT.downlooking.z: depth bins, in meters below the wave-following surface, for the velocity profiles

SWIFT.signature: as above, but from a Nortek Signature, rather than an Aquadopp.  These are version 4 buoys.
	Note that L2 products can have a "velocity reference" field, 
	(if the signature profiles have been mapped from the drifting reference frame to an earth reference frame.) 

SWIFT.winddirT: true wind direction, in degrees FROM North

SWIFT.winddirTstddev: standard deviation of true wind direction, in degrees

SWIFT.windspd: wind speed, in m/s, at 1 m height above the wave-following surface

SWIFT.windspdstddev: standard deviation, in m/s, of wind speed

SWIFT.time: UTC timestamp in MATLAB datenum format (serial days since 0 Jan 0000)

SWIFT.date: human readable date as day, month, year

SWIFT.airtemp: air temperature, in deg C, at 1 m height above the wave-following surface

SWIFT.airtempstddev: standard deviation of air temperature, in deg C

SWIFT.airpres: air pressure at 1 m height above the wave-following surface

SWIFT.airpresstddev: standard deviation of air pressure at 1 m height above the wave-following surface

SWIFT.sigwaveheight: significant wave height, in meters

SWIFT.peakwaveperiod: peak of period orbital velocity spectra (note convention is usually wave height spectrum)

SWIFT.peakwavedirT: wave direction at peak of wave energy spectra, in degrees FROM North

SWIFT.wavespectra.energy: wave energy spectral density, in m^2/Hz, as a function of frequency.  Note that this is derived from orbital motions and is thus insensitive to low-energy swell conditions.  The technique is best suited to measuring short wind waves. 

SWIFT.wavespectra.freq: spectral frequencies, in Hz

SWIFT.wavespectra.a1: normalized spectral directional moment (positive east)

SWIFT.wavespectra.b1: normalized spectral directional moment (positive north)

SWIFT.wavespectra.a2: normalized spectral directional moment (east-west)

SWIFT.wavespectra.b2: normalized spectral directional moment (north-south)

SWIFT.wavespectra.check: spectral comparison of horizontal to vertical motion (only available with post-processing).  Should be equal to 1 for good data in deep water.

SWIFT.lat: latitude in decimal degrees

SWIFT.lon: longitude in decimal degrees

SWIFT.watertemp: water temperature, in deg C, at 0.5 m below the surface

SWIFT.salinity: water salinity, in PSU, at 0.5 m below the surface

SWIFT.puck: three color channels of a WetLabs puck flourometer

SWIFT.driftdirT: drift direction TOWARDS, in degrees True (equivalent to "course over ground")

SWIFT.dirftspd: drift speed in m/s (equivalent to "speed over ground")

SWIFT.O2conc: oxygen concentration 

SWIFT.FDOM: fluorescent dissolved organic material 

SWIFT.z: raw vertical displacements in meters 

SWIFT.x: raw horizontal east-west displacements in meters

SWIFT.y: raw horizontal east-west displacements in meters

SWIFT.u: raw east-west GPS velocities in m/s

SWIFT.v: raw north-south GPS velocities in m/s

SWIFT.rawtime: raw UTC timestamps in Matlab datenum