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

Short name	Standard name	Dimensions	Comments
TIME	time	TIME	Units in Days since reference time specified in variable attribute
Z_DIST	distance_from_sensor_along_vertical	Z_DIST	bin centre distance (in meters) from the transducer along the instrument's vertical axis
N_BEAM	unique_identifier_for_each_beam	N_BEAM	Array of 1 to number of beams (3 to 5 typically)

Variables

Required variables

Short name	Standard name	Dimensions	Comments and units
R_VEL	water_radial_velocity_of_scatterers_ towards_instrument	TIME, Z_DIST, N_BEAM	Units in m/s
R_VEL_FLAGS	water_radial_velocity_of_scatterers_ towards_instrument_status_flag	TIME, Z_DIST, N_BEAM	Boolean flags (8 bit, 0-255) to represent one of 8 possible reasons for rejection. Link to own flagging page
THETA	beam_angle_from_instrument_z_axis	N_BEAM	Units in degrees, positive (usually ~20-30[math]\displaystyle{ ^\circ }[/math])
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.
Quality-control variables recorded by acoustic-Doppler instruments [math]\displaystyle{ \ddagger }[/math]
ABSIC	backscatter_intensity	TIME, Z_DIST, N_BEAM	Units of counts
CORR	correlation_magnitude_from_each_acoustic_beam	TIME, Z_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 [math]\displaystyle{ \dagger\dagger }[/math]
BURST_NUMBER	unique_identifier_for_each_burst	TIME	Integers of 1, 2, etc to designate which burst the velocities are associated with. Only required when measuring in burst-mode.
PROFILE_NUMBER	unique_identifier_for_each_profile	TIME	This variable identifies each record (velocity) profile
[math]\displaystyle{ \ddagger }[/math] Quality-control variable names are consistent for those onboard RDI Teleydyne ADCPs. Nortek has CORRN (noise correlation as a % instead of counts) 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] BURST_NUMBER is only required when measuring in bursts e.g., 18 min of continuous measurements every hour. Can omit if continuously sampled. PROFILE_NUMBER is essentially an integer proxy for TIME.

Optional ancillary variables

Short name	Standard name	Dimensions	Comments
PRES	sea_water_pressure	TIME	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)

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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