View source for Level 3 data (velocity profilers)

{{ReviewStage
|toreview=Ready for review
|authors=Cynthia
|instrument_type=Velocity profilers
}}
[[File:SF atomix ADCP.png|300px|thumb|Schematic of ADCP processing nomenclature]]
The required dimensions and variables for the structure-function processing level within NetCDF ATOMIX format for velocity ADCP measurements are described below.  This NetCDF group contains the structure function (DLL) calculated as a function of the along-beam separation for the available/usable ADCP bins. 

 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 {{FontColor|bg=#fca1fd|text= [[NetCDF_parameter|complete list]]}} for the additional attributes related to each variable (e.g., units, bounds, cell_methods).

__TOC__

=Dimensions=
{| class="wikitable sortable"
|-
! Short name
! Standard name
! Dimensions
! Comments
|-
| TIME
| time
| TIME
| Units in Days since 1950-01-01T00:00:00Z. Provide bounds attribute to designate the variable containing the limits of each segment ([http://cfconventions.org/cf-conventions/v1.6.0/cf-conventions.html#methods-applied-to-a-timeseries-ex see CF-compliant example]).
|-
| Z_DIST
| distance_from_sensor_along_z_instrument_axis
| Z_DIST
| bin centre distance (in meters) from the transducer along the instrument's vertical axis
|-
| R_DEL
| along-beam_separation_distance_
at_which_structure_function_is_evaluated
| R_DEL
| Estimated quantity (in meters) from bin sizes and theta in [[Level_2_qaqc_velocities_(velocity_profilers)#Variables|Level 2 qaqc variables]]
|-
| N_BEAM
| unique_identifier_for_each_beam
| N_BEAM
| Array of 1 to number of beams (3 to 5 typically)
|}
</div>

=Variables=
<div class="mw-collapsible" id="raw" data-collapsetext="Collapse" data-expandtext="Expand variables">
<br>
{| class="wikitable" 
|-
! Short name
! Standard name
! Dimensions
! Comment
|-
| DLL
| second_order_structure_function
| TIME,  R_DIST, R_DEL, N_BEAM
| Differences in velocities squared have been time-averaged (units of m2/s2).
|-
| DLL_FLAGS
| second_order_structure_function_status_flags
| TIME,  R_DIST, R_DEL, N_BEAM
| {{FontColor|fg=white|bg=red|text=To be linked, when boolean flags defined}}
|-
| R_DIST
| distance_from_sensor_along_beams
| Z_DIST, N_BEAM
| Along-beam bin centre distance (in meters) from the transducer 
|-
| DLL_N
| second_order_structure_function_number_of_observations
| TIME,  R_DIST, R_DEL, N_BEAM
| Measure the number of available measurements in each segment i.e., data quality.
|-
| N_SEGMENT
| unique_identifier_for_each_segment_
in_the_entire_available_timeseries
| TIME
| Enables backtracking to [[Level 2 segmented (velocity profilers)|previous processing level]]
|-
| BURST_NUMBER <math>\dagger\dagger</math>
| unique_identifier_for_each_burst
| TIME
| Only required when measuring in burst-mode. Integers of 1, 2, etc to designate which burst the velocities are associated with.
|-
| colspan="4" | 
<math>\dagger\dagger</math> Optional variable required only when measuring in bursts e.g., 18 min of continuous measurements every hour.
|} 
</div>

=Group attributes (metadata)=
<div class="mw-collapsible"  id="raw_att" data-expandtext="Expand group attributes" data-collapsetext="Collapse attributes">

This section describes attributes that may provide additional information about how the data was processed and manipulated at this stage.


{| class="wikitable" 
|-
! Attribute name
! Purpose
! Suggested content
|-
| processing_level
| Boilerplate about the content of the NetCDF group.
| <blockquote>''This group includes the structure function Dll as a function of the separation distance.  Any ancillary information required for estimating the dissipation of turbulent kinetic energy may also be stored here. ''</blockquote>
|-
| dll_calculation_type
| Specify differencing technique used to estimate DLL
| Examples include:
	<blockquote>Central-differencing</blockquote>
    <blockquote>Forward-differencing</blockquote>
|-
| colspan="4" style="text-align:center; font-weight:bold; background-color:#f9eddd"|  Optional group attributes <math>\ddagger</math>
|-
| stationarity_testing
| Any testing done on the segment to verify stationarity?
| {{FontColor|fg=white|bg=red|text=To be revisited once testing begins}}. Tentatively refer to [https://bitbucket.org/efm_cb/netcdf/src/master/TestData/adcp_atomix_metada.yml demo yaml] file.
|-
| noise_testing
| Details of testing the noise levels, or if the signal comprises mostly of noise?
| 
|-
| comment (optional)
| Any additional information pertinent to other users who test their algorithms against the file.
| 
|}
</div>

----
Return to [[Level 2 data (velocity profilers)| Level 2 segmented velocities]]

Go to [[Level 4 data (velocity profilers)| Level 4 dissipation estimates]]