Level 1 data (shear probes)

Minimum and desirable data set

Expand

• The absolute minimum signals and information required to estimate the rate of dissipation of kinetic energy consists of:

• a sampled shear-probe signal,
• a means of determining the speed of flow past the shear probe, and
• a means to estimate the temperature of the fluid so that you can determine its kinematic viscosity.

The sampling rate of the shear-probe signal should exceed significantly (by a factor of 2 to 4) the value of 150U, where U is the speed of the flow past the shear-probe. This speed is often called the speed of profiling, even when the probe is fixed in space and the current causes fluid to flow past the shear probe. The value of 150 cpm equals the spatial resolution of the commonly used shear probe.

• The desirable data set

A far more desirable, but not absolutely necessary, set of data consists of the following.

• Two or more shear probes for measurement redundancy.
• Vibration sensors or accelerometers that are sensitive to the directions of sensitivity of the shear probes.
• An accurate thermometer.
• A pressure transducer.
• A signal that can be used to estimate the speed of flow past the shear probe.
• Pitch and roll sensors.

Most commonly available instruments carry two shear probes that are frequently oriented so that they measure orthogonal components of the shear and, thus, provide two independent estimates of the rate of dissipation that you should agree statistically.

Level 1 data (shear probes)

---

TO DO: Fit the parameter names and definitions to the NetCDF parameter attributes

---

Level 1 data refers to the full resolution data in physical units, e.g. the regularly sampled time series of converted shear probe data. If needed, a transfer function for shear is given. Below, a table with parameters included in the level 1 data set is compiled.

Expand

Dimensions

Example of collapsible table

Short name	Standard name	description
TIME	Days since 1950-01-01 00:00:00 UTC	microstructure sampling rate
TIME_CTD	Days since 1950-01-01 00:00:00 UTC	CTD sampling rate.
TIME_VIB	Days since 1950-01-01 00:00:00 UTC	Vibration sensor sampling rate
TIME_ACCEL	Days since 1950-01-01 00:00:00 UTC	Accelerometer sampling rate.
TIME_???	Days since 1950-01-01 00:00:00 UTC	Sampling rate different than microstructure sampling rate.
N_SHEAR_SENSORS	number of shear channel
N_???_SENSORS	number of ??? channel

Required Variables

Parameter Name	Standard Name	Units of measurement	dimension
TIME	time	days since 1950-01-01 00:00:00 UTC	TIME	1
SHEAR	water_velocity_shear	s-1	[TIME, n_shear_sensors]	1

Optional Level 1 Variables

Parameter Name	Standard Name	Units of measurement	dimension
VIB	platform_vibration	NA	[TIME_VIB, N_VIB_SENSORS]
ACC	platform_acceleration	m s-2	[TIME_ACCEL, N_ACC_SENSORS]
TEMP	sea_water_temperature (water_temperature)	degree_Celsius	[TIME_CTD,N_T_SENSORS
CNCD	sea_water_electrical_conductivity (water_electrical_conductivity)	S m-1	[TIME_CNCD,N_C_SENSORS]
GRADT	temperature_gradient		[TIME_GRADT, N_GRADT_SENSORS]
GRADC	conductivity_gradient		[TIME_GRADC, N_GRADC_SENSORS]
PITCH	platform_pitch_angle	degree	[TIME_PITCH]
ROLL	platform_roll_angle	degree	[TIME_ROLL]

---

return to Dataset requirements for shear probes.

Expand archive

Numbers in the last column indicate:

required=1 are the absolute minimum parameter required for a data set

required=2 are preferred/recommended parameter

required=3 are optional parameter

Parameter Name	CF parameter	Standard Name	Units of measurement	dimension	required
TIME	1	time	days since 1950-01-01 00:00:00 UTC	TIME	1
SHEAR	0	water_velocity_shear	s-1	[TIME, N_SHEAR_SENSORS]	1
PRES	1 0	sea_water_pressure water_pressure	dbar	TIME_CTD	1,2
VIB	0	platform_vibration	NA	[TIME_VIB, N_VIB_SENSORS]	2
ACC	0	platform_acceleration	m s-2	[TIME_ACCEL, n_acc_sensors]	2
TEMP	1 (0)	sea_water_temperature (water_temperature)	degree_Celsius	[TIME_CTD,n_T_sensors]	2
CNCD	1 (0)	sea_water_electrical_conductivity (water_electrical_conductivity)	S m-1	[TIME_CNCD,n_C_sensors]	2
GRADT		temperature_gradient		[TIME_GRADT, n_gradT_sensors]	3
GRADC		conductivity_gradient		[TIME_GRADC, n_gradC_sensors]	3
PITCH	1	platform_pitch_angle	degree	[TIME_PITCH]	2
ROLL	1	platform_roll_angle	degree	[TIME_ROLL]	2