AMOCatlas AC-0.1 Manual

This document defines the AC (AMOC Community) standard data format which is an OceanSITES variant with small deviations. This format provides interoperability between moored estimates of overturning transport from the RAPID, OSNAP, MOVE and SAMBA arrays and other data products which product ocean transports while ensuring compliance with international oceanographic data standards. Note the deviations below (2.1 Deviations from OceanSITES Standard).

Related Documentation:

• Overview (Draft) - AC-0.1 format specification (overview)

• Variables - Variable naming conventions and standards

• Units - Unit definitions and conversions

• Variable Summary (auto-generated) - Auto-generated variable mapping tables

This document provides the detailed implementation guide for AC-0.1, while the above documents provide quick references.

1. Overview & Context

The AC-0.1 format incorporates OceanSITES-1.4 while specifying additional metadata (vocabularies) and standardised naming conventions.

The AC-0.1 format provides compliance with:

• Standards Compliance: Implements CF Conventions 1.8, OceanSITES-1.4, and ACDD 1.3

• Discoverability: Rich metadata using controlled vocabularies

• Workflow Integration: Compatible with existing AMOCatlas workflows

• International Interoperability: Compliance with OceanSITES

• Provenance Tracking: Comprehensive attribution to original data providers

• Extensibility: Supports future variables and array additions

1.1 Relationship to Standards

The AC-0.1 format represents the standardization level in the AMOCatlas hierarchy:

Native Formats → Internal standardised → AC-0.1 Standard
(original)          (atlas internal)     (format_AC-0.1)

Compliance Framework: AC-0.1 datasets are designed to meet:

• CF Conventions 1.8 compliance (validation tools available)

• OceanSITES-1.4 compatibility (with documented deviations as specified in 2.1 Deviations from OceanSITES Standard)

• AMOCatlas-specific validation rules (see amocatlas.compliance_checker)

• ACDD-1.3 metadata structure

Standards Integration: The format integrates multiple international standards:

• CF Conventions 1.8: Climate and Forecast metadata conventions

• OceanSITES-1.4: Ocean observing time series data format

• ACDD 1.3: Attribute Convention for Data Discovery

• NERC Vocabularies: Controlled vocabularies for oceanographic parameters

2. Key Design Decisions

The AC-0.1 format incorporates several design decisions that enhance interoperability while maintaining scientific accuracy and usability.

2.1 Deviations from OceanSITES Standard

AC-0.1 implements OceanSITES-1.4 with the following deviations optimized for AMOC array data:

Deviations from OceanSITES Standard

Feature	OceanSITES Standard	AC-0.1 Format
Contributor Metadata	creator_*, principal_investigator_*	contributor_* attributes (unified pattern)
Density Coordinates	Depth/pressure coordinates only	SIGMA0, SIGMA2 coordinates allowed (array-specific)
Component Dimension	Not specified	N_COMPONENT for transport decomposition
Coordinate Units	degrees_north, degrees_east	degree_north, degree_east (UDUNITS-2, CF-1.8 compliant)
Transport Units	Sv for transport	Sverdrup (avoids confusion with sievert)

Rationale for Deviations:

• Contributor Pattern: Unified contributor_* approach simplifies metadata management while providing equivalent functionality

• Sigma Coordinates: Essential for density-based transport calculations in some arrays

• Component Dimension: Enables systematic representation of transport decompositions across arrays (not yet implemented)

• Coordinate Units: UDUNITS-2 singular forms provide better tool compatibility than OceanSITES plural forms, also compliant with CF-1.8

• Sverdrup Unit: Full spelling prevents confusion with Sv (sievert radiation unit)

These deviations maintain CF compliance and ISO 8601 compatibility while optimizing for AMOC-specific scientific requirements.

3. File Organisation & Naming

3.1 File Naming Convention

Files follow the OceanSITES naming pattern with AMOC-specific modifications:

Basic Pattern: OS_[PLATFORM_CODE]_[DEPLOYMENT]_[MODE]_[PARAMS].nc

Components:

• OS = OceanSITES prefix (maintains compatibility)

• [PLATFORM_CODE] = Platform identifier derived from processing_datasource (e.g., “RAPID26N”, “OSNAP55N”, “MOVE16N”)

• [DEPLOYMENT] = Deployment code (e.g., “20040401-20230211” for date range)

• [MODE] = Data mode: R (real-time), P (provisional), D (delayed-mode)

• [PARAMS] = Parameter identifier (e.g., “transports_T12H”, “sections_T1M”)

Examples:

• OS_RAPID26N_20040401-20230211_D_transports_T12H.nc - Delayed-mode transport data

• OS_OSNAP55N_20140801-20200601_D_sections_T1M.nc - Delayed-mode section data

• OS_MOVE16N_20040201-20181201_D_transports_T12H.nc - Delayed-mode transport data

Reference: See OceanSITES file naming in “4.1.1 Deployment Data files Naming Convention” of the OceanSITES manual (https://ocean-uhh.github.io/oceanarray/oceanSITES_manual.html#data-files).

4. Global Attributes

Following OceanSITES 1.4, ACDD 1.3, and CF 1.8 requirements for comprehensive metadata.

Note

Requirement Status: M = Mandatory, HD = Highly Desired, S = Suggested

4.1 Discovery and Identification

Discovery and Identification Attributes

Attribute	Example	Description	Vocabulary	RS
platform_code	“RAPID26N”	OceanSITES site identifier	OceanSITES Registry	M
array	“RAPID”	Array grouping identifier	Custom AMOCatlas	M
data_mode	“D”	Data mode: R=real-time, P=provisional, D=delayed	OceanSITES Standard	M
title	“RAPID-MOCHA Transport Time Series”	Human-readable dataset title	Free text	HD
theme	“Transport Moored Arrays”	OceanSITES theme classification	OceanSITES Themes	S
naming_authority	“io.github.amoccommunity”	Authority providing the dataset ID	Reverse DNS recommended	S
id	“OS_RAPID26N_20040402-20240327_DPR_transports_T12H”	Unique dataset identifier (filename without .nc)	OceanSITES Pattern	M
summary	“Oceanographic mooring data from the RAPID array at 26°N…”	Extended description for discovery (≤100 words)	Free text	S
source	“subsurface mooring”	Platform type from controlled vocabulary	SeaVoX L06	HD
keywords	“EARTH SCIENCE > Oceans > Ocean Circulation”	Discovery keywords (comma-separated)	GCMD preferred	S
keywords_vocabulary	“GCMD Science Keywords”	Vocabulary source for keywords	Standards reference	S
comment	“Preliminary version; subject to revision”	Miscellaneous information	Free text	S

4.2 Provenance

Consolidates OceanSITES creator_* and principal_investigator_* fields into unified contributor_* attributes supporting multiple contributors following OG1 patterns.

Contributor and Attribution Attributes

Attribute	Example	Description	Vocabulary	RS
contributor_name	“Jane Doe, John Smith”	Names of dataset contributors (comma-separated)	Free text	M
contributor_email	“jane.doe@example.org, john.smith@noc.ac.uk”	Email addresses (aligned with names)	Email format	M
contributor_id	“https://orcid.org/0000-0002-1825-0097, …”	Persistent IDs (ORCID preferred)	ORCID/ISNI URLs	HD
contributor_role	“originator, principalInvestigator”	Roles (aligned with names)	NERC G04	M
contributor_role_vocabulary	“https://vocab.nerc.ac.uk/collection/G04/current/”	Vocabulary for contributor roles	Standards reference	M
contributing_institutions	“University of Hamburg (IfM), National Oceanography Centre (Southampton)”	Institutional contributors	Free text	M
contributing_institutions_vocabulary	“https://ror.org/”	Institutional identifier vocabulary	ROR/EDMO preferred	HD
contributing_institutions_role	“operator, dataProvider”	Institutional roles	NERC W08	M
contributing_institutions_role_vocabulary	“https://vocab.nerc.ac.uk/collection/W08/current/” or “https://vocab.nerc.ac.uk/collection/G04/current/”	Vocabulary for institutional roles	Standards reference	M

Standard Contributor Roles (NERC G04): originator, principalInvestigator, author, coAuthor, contributor, publisher, custodian, owner, pointOfContact

Provenance and Source Attribution

Attribute	Example	Description	Format	RS
acknowledgment	“RAPID data collected and made freely available by the RAPID program…”	Attribution to original data providers (comma-separated)	Free text	M
doi	“https://doi.org/10.35090/gatech/70342, https://doi.org/10.1029/2018GL077408”	DOIs of source datasets (comma-separated)	DOI URLs	M
processing_version	“0.2.0”	Version of processing software used	Semantic version	M
weblink	“https://www.rapid.ac.uk/, https://www.o-snap.org/”	Links to project websites (comma-separated)	URLs	S
start_date	“2004-04-02T00:00:00Z”	Overall dataset start time	ISO 8601	M

4.3 Geospatial and Temporal Coverage

Time Format Rationale: The compact YYYY-mm-ddTHH:MM:ssZ format reduces attribute string length while maintaining human readability and ISO 8601 compatibility.

File dates: The file dates, date_created and date_modified, are our interpretation of the file dates as defined by ACDD. Date_created is the time stamp on the original dataset, date_modified may be used when e.g. metadata is added or the file format is updated.

Geospatial extents: (geospatial_lat_min, max, and lon_min, max) are preferred to be stored as strings for use in the GDAC software, however numeric fields are acceptable. This information is linked to the site information, and may not be specific to the platform deployment.

4.4 Publication and Licensing

4.5 Technical and Processing Information

Technical and Processing Attributes

Attribute	Example	Description	Format	RS
featureType	“timeSeries” or “timeSeriesProfile”	CF discrete sampling geometry type	CF Standard	M
data_type	“OceanSITES time-series data”	OceanSITES data type classification	OceanSITES Standard	M
format_version	“AC-0.1”	AMOCatlas format version	Version string	M
Conventions	“CF-1.8, OceanSITES-1.4, ACDD-1.3”	Metadata conventions followed	Standards list	S
QC_indicator	“excellent”	Overall quality assessment	OceanSITES QC levels	S
processing_level	“Data verified against model or other contextual information”	Processing level description	OceanSITES levels	S
date_created	“2025-01-15T10:30:00Z”	File creation timestamp	ISO 8601	M
date_modified	“2025-01-15T10:30:00Z”	Last modification timestamp	ISO 8601	S
history	“2025-01-15T10:30:00Z: Converted to AC1 using amocatlas v0.3.0”	Processing history log	Timestamped entries	S

5. Dimensions & Coordinates

Following CF conventions, dimensions are ordered as T, Z, Y, X with component dimensions leftmost:

Dimension Ordering

Category	Dimensions	Description
Component	N_COMPONENT	Transport components (optional)
Temporal	TIME	Time coordinate (unlimited)
Vertical	DEPTH, PRESSURE, SIGMA0, SIGMA2	Vertical coordinates (optional)
Horizontal	LATITUDE, LONGITUDE, LATITUDE_BOUNDS, LONGITUDE_BOUNDS	Horizontal coordinates (optional)

Warning

All datasets must include the TIME dimension. Other dimensions are optional depending on data type (timeSeries vs timeSeriesProfile).

6. Data Variables & QC

6.1 Transport Variables

Transport Variables

Variable Name	Variable Attributes	RS
MOC Data Type: float32 Dimensions: TIME	long_name = “MOC_z” standard_name = “ocean_meridional_overturning_streamfunction” units = “Sverdrup” vocabulary = “https://vocab.nerc.ac.uk/collection/P07/current/CFSN0466/” coordinates = “TIME, LONGITUDE, LATITUDE, DEPTH” (required if variable does not have 4 coordinates in its definition) _FillValue = NaNf valid_min = -50.0 (optional) valid_max = 50.0 (optional)	HD
MOC_SIGMA0 or MOC_SIGMA2 Data Type: float32 Dimensions: TIME	long_name = “MOC_sigma0” or “MOC_sigma2” (depending on vertical coordinate used) standard_name = “ocean_meridional_overturning_streamfunction” units = “Sverdrup” vocabulary = “https://vocab.nerc.ac.uk/collection/P07/current/CFSN0466/” coordinates = “TIME, LONGITUDE, LATITUDE, SIGMA0” or “SIGMA2” (required if variable does not have 4 coordinates in its definition) _FillValue = NaNf valid_min = -50.0 (optional) valid_max = 50.0 (optional)	HD
TRANS_* Data Type: float32 Dimensions: N_COMPONENT, TIME	long_name = “Transport” standard_name = “ocean_volume_transport_across_line” units = “Sverdrup” vocabulary = “http://vocab.nerc.ac.uk/collection/P07/current/W946809H/” coordinates = “TIME, LONGITUDE, LATITUDE, DEPTH” (required if variable does not have 4 coordinates in its definition) _FillValue = NaNf	HD
MHT Data Type: float32 Dimensions: TIME	long_name = “MHT” standard_name = “northward_ocean_heat_transport” units = “PW” vocabulary = “http://vocab.nerc.ac.uk/collection/P07/current/CFSN0483/” coordinates = “TIME, LONGITUDE, LATITUDE, DEPTH” (required if variable does not have 4 coordinates in its definition) _FillValue = NaNf valid_min = -5.0 (optional) valid_max = 5.0 (optional)	S
MHT_GYRE Data Type: float32 Dimensions: TIME	long_name = “MHT_gyre” standard_name = “northward_ocean_heat_transport_due_to_gyre” units = “PW” vocabulary = “https://vocab.nerc.ac.uk/collection/P07/current/CFSN0486/” coordinates = “TIME, LONGITUDE, LATITUDE, DEPTH” (required if variable does not have 4 coordinates in its definition) _FillValue = NaNf valid_min = -5.0 (optional) valid_max = 5.0 (optional)	S
MHT_OT Data Type: float32 Dimensions: TIME	long_name = “MHT_ot” standard_name = “northward_ocean_heat_transport_due_to_overturning” units = “PW” vocabulary = “https://vocab.nerc.ac.uk/collection/P07/current/CFSN0487/” coordinates = “TIME, LONGITUDE, LATITUDE, DEPTH” (required if variable does not have 4 coordinates in its definition) _FillValue = NaNf valid_min = -5.0 (optional) valid_max = 5.0 (optional)	S
MFT Data Type: float32 Dimensions: TIME	long_name = “MFT” standard_name = “northward_ocean_freshwater_transport” units = “Sverdrup” vocabulary = “http://vocab.nerc.ac.uk/collection/P07/current/CFSN0507/” coordinates = “TIME, LONGITUDE, LATITUDE, DEPTH” (required if variable does not have 4 coordinates in its definition) _FillValue = NaNf valid_min = -5.0 (optional) valid_max = 5.0 (optional)	S

6.2 Hydrographic Variables

6.3 Descriptive Variables

Descriptive Variables (Component Transport Arrays)

Variable Name	Variable Attributes	RS
TRANSPORT_NAME data type: |S64 (string) dimensions: (N_COMPONENT)	long_name = “Transport component names” coordinates = “N_COMPONENT” content = “Short descriptive names (e.g., Ekman, UMO, AMOC, Florida_Current)”	HD
TRANSPORT_DESCRIPTION data type: |S256 (string) dimensions: (N_COMPONENT)	long_name = “Transport component descriptions” coordinates = “N_COMPONENT” content = “Detailed descriptions of transport components”	S

Note

Requirement Status: M = Mandatory, HD = Highly Desired, S = Suggested

6.4 Variable-Level Quality Control

For variables requiring quality control, implement OceanSITES QC conventions:

Quality Control Variables

QC Variable	Dimensions	Attributes and Values	RS
<PARAM>_QC	Same as parent variable	Data Type: byte Attributes: long_name = “Quality flag for <parameter_name>” flag_values = [0, 1, 2, 3, 4, 7, 8, 9] flag_meanings = “unknown good_data probably_good_data potentially_correctable_bad_data bad_data nominal_value interpolated_value missing_value” valid_min = 0 valid_max = 9	S
<PARAM>_UNCERTAINTY	Same as parent variable	Data Type: float32 Attributes: long_name = “Uncertainty estimate for <parameter_name>” units = Same as parent variable technique_title = “Description of uncertainty estimation method”	S

7. Conversion Tools and Implementation

7.1 Enhanced Conversion Function

To produce AC1 compliant datasets from standardized inputs:

from amocatlas.convert import to_AC1

# Convert with enhanced metadata
ds_ac1 = to_AC1(
    ds_standardized,
    array_metadata_yaml="metadata/rapid_array.yml",
    validate=True,
    gdac_compliant=True
)

7.2 Conversion Process

The conversion function performs these operations:

1. Input Validation: Verify standardized dataset structure

2. Metadata Integration: Load and apply array-specific YAML metadata

3. Attribute Enhancement: Add comprehensive global attributes following OceanSITES/ACDD standards

4. Variable Standardization: Ensure proper standard names, units, and vocabularies

5. Quality Control: Apply QC flags and uncertainty estimates where available

6. File Naming: Generate OceanSITES-compliant filename

7. Compliance Validation: Run CF Checker and OceanSITES validation

8. Output Generation: Write NetCDF4 file with optimal compression and chunking

7.3 Validation Tools

All AC datasets must pass comprehensive validation:

Validation Checks

Validation Category	Requirements
File Naming	Must match OceanSITES pattern: OS_[PSPANCode]_[StartEndCode]_[ContentType]_[PARTX].nc
Global Attributes	All mandatory (M) attributes must be present with valid values
Coordinate Variables	TIME dimension required; appropriate axis attributes; valid units
Data Variables	Valid standard_name attributes; UDUNITS-2 compliant units; appropriate _FillValue
CF Compliance	Must pass CF Checker with zero errors
OceanSITES Compliance	Must meet OceanSITES 1.4 requirements for GDAC submission
Vocabulary Compliance	All controlled vocabulary references must resolve to valid terms

from amocatlas.validation import validate_AC_proposed

# Comprehensive validation
validation_result = validate_AC_proposed(
    "OS_RAPID_20040402-20240327_DPR_transports_T12H.nc",
    checks=["cf", "oceansites", "acdd", "amocatlas"]
)

if validation_result.is_valid:
    print("Dataset is fully compliant with AC1 format")
else:
    print("Validation errors:", validation_result.errors)

8. Examples and Use Cases

8.1 RAPID Transport Time Series Example

File: OS_RAPID_20040402-20240327_DPR_transports_T12H.nc

netcdf OS_RAPID_20040402-20240327_DPR_transports_T12H {
dimensions:
    TIME = UNLIMITED ; // (14600 currently)
    N_COMPONENT = 8 ;
    LATITUDE = 1 ;

variables:
    double TIME(TIME) ;
        TIME:long_name = "Time" ;
        TIME:standard_name = "time" ;
        TIME:units = "seconds since 1970-01-01T00:00:00Z" ;
        TIME:calendar = "gregorian" ;
        TIME:axis = "T" ;

    float LATITUDE(LATITUDE) ;
        LATITUDE:long_name = "Latitude" ;
        LATITUDE:standard_name = "latitude" ;
        LATITUDE:units = "degrees_north" ;
        LATITUDE:valid_min = -90.0f ;
        LATITUDE:valid_max = 90.0f ;
        LATITUDE:axis = "Y" ;

    float MOC_TRANSPORT(TIME) ;
        MOC_TRANSPORT:long_name = "Maximum meridional overturning circulation transport" ;
        MOC_TRANSPORT:standard_name = "ocean_volume_transport_across_line" ;
        MOC_TRANSPORT:units = "sverdrup" ;
        MOC_TRANSPORT:coordinates = "TIME" ;
        MOC_TRANSPORT:_FillValue = NaNf ;
        MOC_TRANSPORT:vocabulary = "http://vocab.nerc.ac.uk/collection/P07/current/W946809H/" ;

    float TRANSPORT(N_COMPONENT, TIME) ;
        TRANSPORT:long_name = "Ocean volume transport components across line" ;
        TRANSPORT:standard_name = "ocean_volume_transport_across_line" ;
        TRANSPORT:units = "sverdrup" ;
        TRANSPORT:coordinates = "TIME" ;
        TRANSPORT:_FillValue = NaNf ;

    string TRANSPORT_NAME(N_COMPONENT) ;
        TRANSPORT_NAME:long_name = "Transport component names" ;
        TRANSPORT_NAME:coordinates = "N_COMPONENT" ;

// global attributes:
        :Conventions = "CF-1.8, OceanSITES-1.4, ACDD-1.3" ;
        :format_version = "1.4" ;
        :data_type = "OceanSITES time-series data" ;
        :featureType = "timeSeries" ;
        :data_mode = "D" ;
        :site_code = "RAPID" ;
        :array = "RAPID" ;
        :platform_code = "RAPID26N" ;
        :naming_authority = "AMOCatlas" ;
        :id = "OS_RAPID_20040402-20240327_DPR_transports_T12H" ;
        :title = "RAPID-MOCHA Transport Time Series at 26°N" ;
        :summary = "Meridional overturning circulation and component transports from the RAPID mooring array at 26°N in the Atlantic Ocean. Data processed to 12-hourly resolution with comprehensive quality control." ;
        :geospatial_lat_min = 26.0 ;
        :geospatial_lat_max = 26.5 ;
        :geospatial_lon_min = -80.0 ;
        :geospatial_lon_max = -13.0 ;
        :time_coverage_start = "2004-04-02T00:00:00Z" ;
        :time_coverage_end = "2024-03-27T23:59:59Z" ;
        :contributor_name = "Dr. David Smeed, Dr. Molly Baringer" ;
        :contributor_email = "david.smeed@noc.ac.uk, molly.baringer@noaa.gov" ;
        :contributor_role = "principalInvestigator, principalInvestigator" ;
        :source_acknowledgement = "RAPID data were collected and made freely available by the RAPID program and the national programs that contribute to it" ;
        :source_doi = "https://doi.org/10.5285/8cd7e7bb-9a20-05d8-e053-6c86abc012c2" ;
        :amocatlas_version = "0.3.0" ;
        :date_created = "2025-01-15T10:30:00Z" ;
        :history = "2025-01-15T10:30:00Z: Converted to AC1 using amocatlas v0.3.0" ;
}

9. Reference Tables

9.1 UDUNITS-2 Compliance

All units must follow the UDUNITS-2 standard for maximum compatibility and interoperability.

Unit Specifications for AC1 Format

Quantity	UDUNITS Format	Notes
Coordinates
Time	seconds since 1970-01-01T00:00:00Z	ISO 8601 epoch reference (Unix timestamp)
Latitude	degree_north	UDUNITS-2 standard (singular form)
Longitude	degree_east	UDUNITS-2 standard (singular form)
Depth	m	Standard SI unit, positive downward
Pressure	dbar	Standard oceanographic unit (decibars)
Density	kg m-3	SI derived unit for sigma coordinates
Physical Variables
Temperature	degree_C	Preferred over degC (full spelling)
Salinity	1	Dimensionless (practical salinity scale)
Velocity	m s-1	SI derived unit (not m/s)
Transport Variables
Ocean Volume Transport	sverdrup	1 sverdrup = 10^6 m³/s (avoid Sv confusion)
Heat Transport	petawatt	1 PW = 10^15 W (preferred over W with scale factors)
Freshwater Transport	sverdrup	Same as volume transport

Warning

Use lowercase sverdrup (not Sv) to avoid confusion with the sievert radiation unit. UDUNITS-2 recognizes sverdrup as the standard oceanographic transport unit.

9.2 OceanSITES Reference table 1: data_type

The data_type global attribute should have one of the valid values listed here.

Data Type Values

Data type
OceanSITES profile data
OceanSITES time-series data
OceanSITES trajectory data

9.3 OceanSITES Reference table 2: QC_indicator

The quality control flags indicate the data quality of the data values in a file. The byte codes in column 1 are used only in the <PARAM>_QC variables to describe the quality of each measurement, the strings in column 2 (‘meaning’) are used in the attribute <PARAM>:QC_indicator to describe the overall quality of the parameter.

When the numeric codes are used, the flag_values and flag_meanings attributes are required and should contain lists of the codes (comma-separated) and their meanings (space separated, replacing spaces within each meaning by ‘_’).

QC Flag Values

Code	Meaning	Comment
0	unknown	No QC was performed
1	good data	All QC tests passed.
2	probably good data
3	potentially correctable bad data	These data are not to be used without scientific correction or re-calibration.
4	bad data	Data have failed one or more tests.
5		Not used
6		Not used.
7	nominal value	Data were not observed but reported. (e.g. instrument target depth.)
8	interpolated value	Missing data may be interpolated from neighboring data in space or time.
9	missing value	This is a fill value

9.4 OceanSITES Reference table 3: Processing level

This table describes the quality control and other processing procedures applied to all the measurements of a variable. The string values are used as an overall indicator (i.e. one summarizing all measurements) in the attributes of each variable in the processing_level attribute.

Processing Level Values

Processing Level
Raw instrument data
Instrument data that has been converted to geophysical values
Post-recovery calibrations have been applied
Data has been scaled using contextual information
Known bad data has been replaced with null values
Known bad data has been replaced with values based on surrounding data
Ranges applied, bad data flagged
Data interpolated
Data manually reviewed
Data verified against model or other contextual information
Other QC process applied

9.5 OceanSITES Reference table 4: Data mode

The values for the variables “<PARAM>_DM”, the global attribute “data_mode”, and variable attributes “<PARAM>:DM_indicator” are defined as follows:

Data Mode Values

Value	Meaning	Description
R	Real-time data	Data coming from the (typically remote) platform through a communication channel without physical access to the instruments, disassembly or recovery of the platform. Example: for a mooring with a radio communication, this would be data obtained through the radio.
P	Provisional data	Data obtained after instruments have been recovered or serviced; some calibrations or editing may have been done, but the data is not thought to be fully processed. Refer to the history attribute for more detailed information.
D	Delayed-mode data	Data published after all calibrations and quality control procedures have been applied on the internally recorded or best available original data. This is the best possible version of processed data.
M	Mixed	This value is only allowed in the global attribute “data_mode” or in attributes to variables in the form “<PARAM>:DM_indicator”. It indicates that the file contains data in more than one of the above states. In this case, the variable(s) <PARAM>_DM specify which data is in which data mode.

9.6 OceanSITES Reference Table 6: Identifying data variables (subset)

OceanSITES Variable Names (subset)

Parameter	CF Standard name or suggested Long name	AC1 Variable Name
CDIR	direction_of_sea_water_velocity	CDIR
CNDC	sea_water_electrical_conductivity	CNDC
CSPD	sea_water_speed	CSPD
DEPTH	depth	DEPTH
DOX2	moles_of_oxygen_per_unit_mass_in_sea_water was dissolved_oxygen	DOX2
DOXY	mass_concentration_of_oxygen_in_sea_water was dissolved_oxygen	DOXY
DOXY_TEMP	temperature_of_sensor_for_oxygen_in_sea_water	DOXY_TEMP
DYNHT	dynamic_height	DYNHT
FLU2	fluorescence	FLU2
HCSP	sea_water_speed	HCSP
HEAT	heat_content	HEAT
ISO17	isotherm_depth	ISO17
PCO2	surface_partial_pressure_of_carbon_dioxide_in_air	PCO2
PRES	sea_water_pressure	PRESSURE
PSAL	sea_water_practical_salinity	PSAL
TEMP	sea_water_temperature	TEMP
UCUR	eastward_sea_water_velocity	UCUR
VCUR	northward_sea_water_velocity	VCUR

11. Future Development and Extensions

• Multi-Array Integration: Support for datasets combining multiple arrays

• Real-Time Data Streams: Extensions for operational oceanography

• Machine-Readable Provenance: Integration with Research Data Alliance metadata standards

• Cloud-Optimized Formats: Zarr and COG variants for cloud computing

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Project Funding: AC1 format development is supported by the Horizon Europe project EPOC - Explaining and Predicting the Ocean Conveyor (Grant Agreement No. 101081012).

Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.