Level 1 data (shear probes)
Contents
Minimum and desirable 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.
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.
Dimensions
Example of collapsible table
| Short name | Standard name |
|---|---|
| TIME | microstructure sampling rate. Days since 1950-01-01 00:00:00 UTC |
| TIME_CTD | CTD sampling rate. Days since 1950-01-01 00:00:00 UTC |
| TIME_VIB | Vibration sensor sampling rate. Days since 1950-01-01 00:00:00 UTC |
| TIME_ACCEL | Accelerometer sampling rate. Days since 1950-01-01 00:00:00 UTC |
| TIME_SLOW1 | Sampling rate slower than microstructure sampling rate. Days since 1950-01-01 00:00:00 UTC |
| N_SHEAR_SENSORS | number of shear 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, 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] |
return to Dataset requirements for shear probes.
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 |
|---|---|---|---|---|---|
| PRES | 1 0 |
sea_water_pressure water_pressure |
dbar | TIME | 1,2 |
| 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 |
| VIB | 0 | platform_vibration | NA | [TIME, n_vibration_sensors] | 2 |
| ACC | 0 | platform_acceleration | m s-2 | [TIME, n_acc_sensors] | 2 |
| TEMP | 1 (0) |
sea_water_temperature (water_temperature) |
degree_Celsius | [TIME,n_T_sensors] | 2 |
| CNCD | 1 (0) |
sea_water_electrical_conductivity (water_electrical_conductivity) |
S m-1 | [TIME_FAST,n_C_sensors] | 2 |
| GRADT | temperature_gradient | [TIME, n_gradT_sensors] | 3 | ||
| GRADC | conductivity_gradient | [TIME, n_gradC_sensors] | 3 | ||
| PITCH | 1 | platform_pitch_angle | degree | [TIME] | 2 |
| ROLL | 1 | platform_roll_angle | degree | [TIME] | 2 |
