Level 4 data (velocity profilers)

Page status: Draft
Author(s):	Cynthia
Reviewer(s):
Comment:

This will dictate the data required at the final processing level, where we store the estimated dissipation estimates $\epsilon$ along with quality metrics.

Dimensions

Short name	Standard name	Dimensions	Comments
TIME	time	TIME	Units in Days since 1950-01-01T00:00:00Z. Provide a bounds attribute to designate the variable containing the limits of each segment (see CF-compliant example).
R_DIST	distance_from_sensor_along_beams	R_DIST	Along-beam bin centre distance (in meters) from the transducer
N_BEAM	unique_identifier_for_each_beam	N_BEAM	Array of 1 to number of beams (3 to 5 typically)
Optional dimensions for 5-beam ADCP
R_DIST5	distance_from_sensor_along_beam_5	R_DIST5	Along-beam bin centre distance (in meters) from the transducer for the 5th vertical beam

Variables

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Short name	Standard name	Dimensions	Comment
EPSI	specific_turbulent_kinetic_energy_dissipation _in_water	TIME, R_DIST, N_BEAM	Dissipation rate of turbulent kinetic energy per unit mass of water [W/kg] estimated from individual beams.
EPSI_FINAL	specific_turbulent_kinetic_energy_dissipation _in_water	TIME, R_DIST	Final dissipation rate of turbulent kinetic energy per unit mass of water (beam-averaged). best to state cell_methods attribute to indicate what was averaged e.g., "cell_methods= N_BEAM:mean" for averages across beams.
C2	constant_used_in_the_second_order_structure_function	Scalar [1 value]	This constant appears when estimating the dissipation rate of turbulent kinetic energy from the regression coefficients.
Quality-control metrics
EPSI_FLAGS	specific_turbulent_kinetic_energy_dissipation_ in_water_status_flags	TIME, R_DIST, N_BEAM	To be linked, when boolean flags defined
EPSI_CI_HIGH	specific_turbulent_kinetic_energy_dissipation_ in_water_high_confidence_limit	TIME, R_DIST, N_BEAM	Specify how error was computed.
EPSI_CI_LOW	specific_turbulent_kinetic_energy_dissipation_ in_water_low_confidence_limit	TIME, R_DIST, N_BEAM	Specify how error was computed.
R_MAX		TIME, R_DIST, N_BEAM	help!
REGRESSION_COEFF_A0		TIME, R_DIST, N_BEAM	help!
REGRESSION_COEFF_A1		TIME, R_DIST, N_BEAM	help!
REGRESSION_R2		TIME, R_DIST, N_BEAM	help!
REGRESSION_N	structure_function_regression_number_of_observations	TIME, R_DIST, N_BEAM	Note the CF-compliant standard name modifier "number_of_observations"
Optional dimensions for 5-beam ADCP
Enter variables here or create a footnote (note that N_BEAM disappears as a dimension for the 5th beam)		TIME, R_DIST5
$††$ Variable required only when measuring in bursts e.g., 18 min of continuous measurements every hour.

Group attributes (metadata)

Collapse attributes

This section describes attributes that may provide additional information about how the data was processed and manipulated at this stage.

Attribute name	Purpose	Suggested content
processing_level	Boilerplate about the content of the NetCDF group.	This group includes the results associated with fitting the structure function to data in level 3. The results for each beam, along with quality indicators and errors are provided. A final estimate for the turbulent kinetic energy dissipation is also provided.
dll_fitting_method	statistical technique used for fitting the spectra.	Examples include: ????
comment (optional)	Any additional information pertinent to other users who test their algorithms against the file.

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