Level 1 data (velocity profilers)

Page status: Ready for review
Author(s):	Cynthia
Reviewer(s):
Comment:

The required dimensions and variables for the first processing level within NetCDF ATOMIX format for ADCP velocity measurements are described below. This processing level contains the raw measurements recorded by the instrument. If sampling is in burst mode, the measurements from individual bursts are appended together.

Only a few attributes for each variable are listed since the page's purpose is to describe the information layout within each NetCDF file. Please refer to the complete list for the additional attributes related to each variable (e.g., units, bounds, cell_methods).

Dimensions

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Short name	Standard name	Dimensions	Comments
TIME	time	TIME	Units in Days since 1950-01-01T00:00:00Z
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
R_DIST5	distance_from_sensor_along_beam_5	R_DIST5	along-beam bin centre distance (in meters) from the 5th beam, which is usually aligned with vertical axis of the ADCP.

Variables

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Required variables

Short name	Standard name	Dimensions	Comments and units
R_VEL	water_radial_velocity_of_scatterers_ towards_instrument	TIME, R_DIST, N_BEAM	Units in m/s
THETA	beam_angle_from_instrument_z_axis	N_BEAM	Units in degrees, positive (usually ~20-30o)
BIN_SIZE	instrument_measurement_volume_bin_size	N_BEAM	vertical size of the ADCP bins. Usually the same for all 4 beams, but 5th beam can vary.
BURST_NUMBER	unique_identifier_for_each_burst	TIME	Integers of 1, 2, etc to designate which burst the velocities are associated with. Can set all to 1 if continuously sampled.
Quality-control variables recorded by acoustic-Doppler instruments [math]\displaystyle{ \ddagger }[/math]
ABSI	backscatter_intensity_from_each_acoustic_beam	TIME, R_DIST, N_BEAM	Units of db
CORR	correlation_magnitude_from_each_acoustic_beam	TIME, R_DIST, N_BEAM	Unit of counts
Platform motion variables[math]\displaystyle{ \dagger }[/math]
HEADING	platform_yaw_angle	TIME	degrees, clockwise from true North
PITCH	platform_pitch_angle	TIME	degrees
ROLL	platform_roll_angle	TIME	degrees
Optional variables for 5-beam ADCP[math]\displaystyle{ \dagger\dagger }[/math]
R_VEL5	water_radial_velocity_of_scatterers_towards_instrument_of_beam_5	TIME, R_DIST5	Units in m/s
[math]\displaystyle{ \ddagger }[/math] Quality-control variable names are consistent for those onboard RDI Teleydyne ADCPs. Not sure for Nortek, perhaps they use the same as their Vectors detailed in the ADV Level 1 variables. [math]\displaystyle{ \dagger }[/math] Motion variables are necessary for structure function analysis for situating the bins relative the vertical (gravity). These variables do enable converting measurements into geographical. [math]\displaystyle{ \dagger\dagger }[/math] 5-beam ADCPs has the 5th beam usually pointing directly up with its own bin sampling height, and may also be sampled at a different rate. In these situations, the data must be stored in separate variables given the different dimensions assigned. Simply append the number 5 to the variable name (e.g., TIME5)

Optional ancillary variables

Short name	Standard name	Dimensions	Comments
PRES	sea_water_pressure	TIME, N_VEL_INSTRUMENT	dbar, equals 0 at the sea surface and positive down.
TEMP*	sea_water_temperature	TIME	degrees_Celsius, in-situ temperature ITS-90 scale
*Data from concurrent sensors may be optionally included e.g., salinity, dissolved oxygen. Kinematic viscosity of seawater needs to be calculated during processing,

Group attributes (metadata)

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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 ATOMIX Level 1 content.	This group includes the raw measurements from the recorder and ancillary measurements required for quality-controlling them using the manufacturer's recommendations.
comment (optional)	Information is pertinent to problems in the raw data files during collection.	Examples: Stitching of files, corruption of binary files that were recovered by the manufacturer, etc.

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