Dataset requirements for shear probes
This page provides an overview of the NetCDF format of benchmark dataset for instruments that measure velocities at a point in space e.g., acoustic-Doppler velocimeters and travel-time velocimeters (MAVS).
Benchmark datasets: Velocity point-measurements
ATOMIX provides several benchmark datasets consisting of four processing levels.
- Raw timeseries
- full resolution data in physical units
- Quality-controlled and segmented timeseries
- full resolution cleaned and despiked parameters from level 1, subdivided in individual sections.
- Spectra
- raw and cleaned spectra
- Dissipation [math]\displaystyle{ \varepsilon }[/math] estimates
- dissipation estimates and corresponding quality parameter as time series
return to Velocity point-measurements
The absolute minimum data set
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.
Recommended data format
For sharing a data set, we recommend providing four processing levels of data in a single netCDF file per instrument file. The processing levels include
The data format recommended is summarized in standard dimensions and should include necessary meta data. ATOMIX provides several benchmark data sets following these guidelines.
This section provides an overview of the NetCDF format of benchmark dataset for instruments that measure microstructure shear.
Raw timeseries
Dimensions
Example of collapsible list
- TIME
- HEIGHT_AS
Example of collapsible table
| Short name | Standard name |
|---|---|
| TIME | days since 1950-01-01 00:00:00 UTC |
| n_shear_sensors | number of shear channel |
| Short name | Standard name |
|---|---|
| Content | Goes |
| In Here | Please |
Required Variables
| Parameter Name | Standard Name | Units of measurement | dimension | |
|---|---|---|---|---|
| PRES | sea_water_pressure water_pressure |
dbar | TIME | 1,2 |
| 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 Variables
| Parameter Name | Standard Name | Units of measurement | dimension |
|---|---|---|---|
| VIB | platform_vibration | NA | [TIME, n_vibration_sensors] |
| ACC | platform_acceleration | m s-2 | [TIME, n_acc_sensors] |
| TEMP | sea_water_temperature (water_temperature) |
degree_Celsius | [TIME,n_T_sensors] |
| CNCD | sea_water_electrical_conductivity (water_electrical_conductivity) |
S m-1 | [TIME_FAST,n_C_sensors] |
| GRADT | temperature_gradient | [TIME, n_gradT_sensors] | |
| GRADC | conductivity_gradient | [TIME, n_gradC_sensors] | |
| PITCH | platform_pitch_angle | degree | [TIME] |
| ROLL | platform_roll_angle | degree | [TIME] |
Group Attributes (metadata)
Required
- Att 1
- Att2
Optional
- Enter here
Quality-controlled and segmented timeseries
Insert info here in the same format as Raw
Spectra
Dissipation
return to Shear probes
