Level 3 data (shear probes)

Level 3 data contains the raw (and optionally cleaned) spectra derived from level 2 time series and is saved in the NetCDF group "L3_spectra". Level 3 parameters are defined along a new TIME dimension, which is the average time of the individual spectral segments. The length of the TIME dimension equals the number of spectral segments. Parameter for the calculation of the spectra, e.g. segment length, are provided in the meta data.

Dimensions

Dimension name	description
TIME_SPECTRA	length of the record of average times of spectral segments. This also equals time of dissipation estimates.
N_WAVENUMBER	length of the wavenumber array
N_SHEAR_SENSORS	number of shear channels (shear sensors)
N_***_SENSORS	number of *** channels (such as ACC and VIB)
N_SH_ACC_SPEC	number of shear-acceleration cross spectra
N_SH_VIB_SPEC	number of shear-vibration cross spectra
N_GLOBAL_VALUES [math]\displaystyle{ ^a }[/math]	dimension for 1 data point (for the entire analysis)

[math]\displaystyle{ ^a }[/math] This dimension is 1x1. Use, for example, for N_FFT_SEGMENTS (number_of_fft_segments), SPEC_STD (standard_deviation_uncertainty_of_shear_spectrum), and is one value for the entire analysis.

Required Variables

Parameter Name	Standard Name	Units of measurement	dimension
TIME	time	CF-Conventions compatible offset[math]\displaystyle{ ^a }[/math]	TIME_SPECTRA
SECTION_NUMBER	unique_identifier_for_each_section_ of_data_from_timeseries	-	TIME_SPECTRA
PSPD_REL	platform_speed_wrt_sea_water	m s-1	TIME_SPECTRA
SH_SPEC	shear_probe_spectrum	s-2 cpm-1	[TIME_SPECTRA, N_WAVENUMBER, N_SHEAR_SENSORS]
KCYC	cyclic_wavenumber	cpm	[TIME_SPECTRA, N_WAVENUMBER]
SH_SPEC_CLEAN[math]\displaystyle{ ^b }[/math]	shear_probe_spectrum_clean	s-2 cpm-1	[TIME_SPECTRA, N_WAVENUMBER, N_SHEAR_SENSORS]
N_FFT_SEGMENTS	number_of_fft_segments	-	N_GLOBAL_VALUES
N_VIB_SENSORS	number_of_vibration_sensors_used_for_cleaning_spectra	-	N_GLOBAL_VALUES
SPEC_STD	standard_deviation_uncertainty_of_shear_spectrum	-	N_GLOBAL_VALUES

[math]\displaystyle{ ^a }[/math] i.e. "Days since YYYY-MM-DDT00:00:00Z"

[math]\displaystyle{ ^b }[/math] SH_SPEC_CLEAN must be included in the file if these spectra were used to compute [math]\displaystyle{ \varepsilon }[/math]

Optional Level 3 Variables

Parameter Name	Standard Name	Units of measurement	dimension
PRES	water_pressure	dbar	TIME_SPECTRA
ACC_SPEC	acceleration_sensor_spectrum	m2 s-4 cpm-1	[TIME_SPECTRA, N_WAVENUMBER, N_ACCEL_SENSORS]
VIB_SPEC	vibration_sensor_spectrum	-	[TIME_SPECTRA, WAVENUMBER, N_VIB_SENSORS]
SH_VIB_SPEC	shear_and_vibration_cross-spectral_matrix	-	[TIME_SPECTRA, N_WAVENUMBER, N_SH_VIB_SPEC]
SH_ACC_SPEC	shear_and_acceleration_cross-spectral_matrix	-	[TIME_SPECTRA, N_WAVENUMBER, N_SH_ACC_SPEC]
DOF	degrees_of_freedom_of_spectrum	-	N_GLOBAL_VALUES

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