Conventions

GTE
NASA Ames
NetCDF

Data format

The following conventions are specified for the format GTE, based on: www-gte.larc.nasa.gov/pem/GTE_FMT98.htm.

General metadata: global attributes

Line 4. species measured / technique used

Naming convention: Please use the acronym or the name of one of these data sources (instruments or models).

Line 5. expedition name

Naming convention: Please use the acronym (name) of one of these missions.

Line 7. number for this flight, or sequential dataset number (NF)

If the mission PI has enter all flights of the mission, HALO-DB can attend the relation of your dataset to the number of the flight. The number of flights you will find in section "ongoing subset" of the page of the concerning mission.

Metadata: variable definition

Item 1. variable name: name of data variable

Naming convention: Please use the name of one of these parameters (based on the CF Metadata convention) wherever applicable.

Data format

The following conventions are specified for the format NASA Ames, based on: espoarchive.nasa.gov/archive/docs/formatspec_2_0.html.

Following this specification some metadata (e.g the unit of the variables) are not supported and can not therefore be specified.

Supported Dialect

Using the version 2 format extensions, more specific information can be placed to particular header lines by the use of the separator '|'.

General metadata: global attributes

SNAME represents a string which specifies the source of the measurements or model.

By default the header element SNAME will declare the data source.
Naming convention: Please use the acronym or the name of one of these data sources (instruments or models).

Supplementary to the data source (instrument or model) SNAME you can declare a category (platform or modeltype) by using the version 2 format extensions .
Naming convention: Please use the acronym or the name of one of these categories (platforms or modeltypes).

1 | platform | instrument |

If you declare more than one pair of a category and a data source, HALO-DB will take only the first category (platform or modeltype) and the first data source (instrument or model).

MNAME is a character string specifying the mission.

Naming convention: Please use the acronym (name) of one of these missions.

Metadata: variable definition

ANAME(a) is a character string, describing the name of the a-th auxiliary variable

By default the header element ANAME will declare the name of a parameter.
Naming convention: Please use the name of one of these parameters (based on the CF Metadata convention) wherever applicable.

Supplementary you can declare a unit by using the version 2 format extensions . In that case ANAME must contain eight substrings separated by '|'.

name1 | name2 | unit | | | | |

HALO-DB concatenates the first and the second substring to the name of the parameter. The third of the ANAME's substring is the unit.

VNAME(n) is a character string, describing the name of the n-th primary variable

By default the header element VNAME will declare the name of a parameter.
Naming convention: Please use the name of one of these parameters (based on the CF Metadata convention) wherever applicable.

Supplementary you can declare a unit by using the version 2 format extensions . In that case VNAME must contain eight substrings separated by '|'.

name1 | name2 | unit | | | | |

HALO-DB concatenates the first and the second substring to the name of the parameter. The third of the VNAME's substring is the unit.

XNAME(s) is a character string, describing the name of the s-th independent variable

By default the header element XNAME will declare the name of a parameter.
Naming convention: Please use the name of one of these parameters (based on the CF Metadata convention) wherever applicable.

Supplementary you can declare a unit by using the version 2 format extensions . In that case XNAME must contain eight substrings separated by '|'.

name1 | name2 | unit | | | | |

HALO-DB concatenates the first and the second substring to the name of the parameter. The third of the XNAME's substring is the unit.

Data format

The following conventions are specified for the format NetCDF, based on: unidata.ucar.edu/software/netcdf.

PLEASE NOTE: NetCDF is a container for various formats and data models. Unfortunately, there are some incompatibilities between different NetCDF software libraries. A NetCDF file generated with one version might not be recognized as NetCDF by a machine or software using another version. HALO-DB works fine with NetCDF-3 classic formats, but the upload parser tends to reject NetCDF-4 hdf5 (e.g. as "Bad Request"). Please contact us, if you run into this and can not go back to NetCDF3.

In general, there are not many restrictions on metadata in NetCDF files. The following is a subset of NetCDF Attribute Convention for Dataset Discovery, constituting the attributes and naming conventions supported by the HALO database.

Keys of necessity

i Suggested attribute

∗ Recommended attribute

! Required or highly recommended attribute

General metadata: global attributes

Acknowledgment

Please use the attribute: acknowledgment.

Author of the dataset

Please use one of these attributes: author, contact, creator_name.

∗

Category - the source of the measurement or the model (see).

Please use one of these attributes: category, source, platform.
Naming convention: Please use the acronym or the name of one of these categories (platforms or modeltypes).

∗

Comment

Please use one of these attributes: comment, description.

∗

Data source - describes the genesis of the data itself (see).

Please use one of these attributes: data_source, experiment, instrument.
Naming convention: Please use the acronym or the name of one of these data sources (instruments or models).

Date last revised provides the date on which the data was last modified.

Please use one of these attributes: date_last_revised, date_modified.

Date created gives the date on which the data was created.

Please use the attribute: date_created.

Institute - the author's institute.

Please use one of these attributes: institute, institution.

Keywords - a comma separated list of key words and phrases.

Please use the attribute: keywords.

License - describes the restrictions to data access and distribution.

Please use the attribute: license.
Naming convention: Please use the acronym of one of these licenses.

∗

Max/min Altitude describes the vertical bounding box.

Vertical is assumed to be in meters above ground.
Please use one of these attributes: max_altitude, geospatial_vertical_max.
Please use one of these attributes: min_altitude, geospatial_vertical_min.

∗

Max/min Latitude describes the north/south bounding box in degrees.

Please use one of these attributes: max_latitude, geospatial_lat_max.
Please use one of these attributes: min_latitude, geospatial_lat_min.
Naming convention: Please use the unit degree in decimals (e.g. '21.8424' or '-55.98').

∗

Max/min Longitude describes the east/west bounding box in degrees.

Please use one of these attributes: max_longitude, geospatial_lon_max.
Please use one of these attributes: min_longitude, geospatial_lon_min.
Naming convention: Please use the unit degree in decimals (e.g. '21.8424' or '-55.98').

∗

Max/min Time describes time coverage.

Please use one of these attributes: start_datetime, time_coverage_start.
Please use one of these attributes: stop_datetime, time_coverage_end.
Naming convention: Please use a datetime string like an ISO8601 date (e.g. '1999-07-04' or '1999-07-04T22:30:05').

Mission - specify the name of the mission.

Please use the attribute: mission.
Naming convention: Please use the acronym (name) of one of these missions.

Name or title of the dataset.

Please use one of these attributes: title, id, naming_authority.

∗

Ongoing subset - also known as number for this flight, or sequential dataset number.

Project - provides the name of the scientific project for which the data was created.

Please use the attribute: project.
Naming convention: Please use the acronym of one of these projects.

Summary - gives a longer description of the dataset.

Please use the attribute: summary.

Metadata: variable definition

Name of the variable.

Please use one of these attributes: parameter, standard_name, long_name.
Naming convention: Please use the name of one of these parameters (based on the CF Metadata convention) wherever applicable.

∗

Unit of the variable.

Please use one of these attributes: unit, original_units, units.

Scale factor of the variable.

Please use one of these attributes: scale, sacle_factor.

Offset of the variable.

Please use one of these attributes: offset, add_offset.

String identify the missing values of the variable.

Please use one of these attributes: nullcode, missing_value.

Max/min values of the variable.

Please use one of these attributes: max, valid_max.
Please use one of these attributes: min, valid_min.

Comment to a variable.

Please use the attribute: comment.

Users who should consider this conventions?

Anyone who prepares files that shall be stored in the HALO-DB.
Authorised users (see about) who want to upload datasets are urged to check that their files meet the HALO-DB conventions. Failure to do so may result in warning messages, ignorance of metadata, or even rejection of the dataset.

Why conventions?

HALO-DB datasets consist of primary data and metadata. The supported data formats (GTE, NASA Ames, NetCDF) support self-contained specifications, but the level of detail of metadata information might differ significantly between files.

The supported data formats in general allow different dialects, and to some degree arbitrary metadata. For a successful parsing (metadata processing of the datasets) it is necessary to declare some conventions. The HALO-DB conventions are format dependent and go conform with the particular format specification.
Some of the conventions are mandatory for successful upload. Others just allow automatic extraction of detailed information, which is then evaluated and provided by the HALO-DB.