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Along this document some issues are still at some level under discussion. To mark this the following color coding is used
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Encoding Guide
Global attributes
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| Attribute Name | Value | Examples | Comment | |
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| Conventions | CF_convention_string C3S-0.1 [Other convention] :... | "CF-1.6 C3S-0.1" | Multiple conventions may be included (separated by blank spaces) | |
| title | A controlled vocabulary will be provided CF: Free text ACDD (highly recommended) | "IPSL-CM5A-LR model output prepared for CMIP5 RCP4.5" | A short phrase or sentence describing the dataset. In many discovery systems, the title will be displayed in the results list from a search, and therefore should be human readable and reasonable to display in a list of such names | |
| references | URIs (such as a URL or DOI) for papers or other references. A valid doi is recommended CF: Free text | "doi:10.5194/gmd-8-1509-2015" | Published or web-based references that describe the data or methods used to produce it. | |
| source | A methodology to build this attribute will be provided |
| The method of production of the original data. If it was model-generated, source should name the model and its version, as specifically as it could be useful | |
| institution | A controlled vocabulary will be provided CF: Free text
| "Met Office" | Specifies where the original data was produced. The name of the institution principally responsible for originating this data. | |
| contact | Copernicus User Support URI should be used CF: Free text | "http://copernicus-support.ecmwf.int" |
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| project | "C3S Seasonal Forecast" should be used CF: Free text
| "C3S Seasonal Forecast" | ||
| creation_date | SPECS: YYYY-MM-DDThh:mm:ss<zone> ISO 8601:2004 extended format | "2011-06-24T02:53:46Z" | The date on which this version of the data was created. Modification of values implies a new version, hence this would be assigned the date of the most recent values modification. Metadata changes are not considered when assigning the creation_date NOTE: The ACDD 1.3 names this attribute as date_create | |
| comment | Free text |
| Miscellaneous information about the data, not captured elsewhere. | |
| forecast_type | "forecast" or "hindcast" | "forecast" | To identify the type of data
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| history | Each line should begin with a timestamp indicating the date and time of day when the program was executed CF: Free Text |
| To record relevant information, such as the command history which led to this file being produced. Provides an audit trail for modifications to the original data.
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commit, iso_lineage or lineage | Free text (ISO Lineage model 19115-2) | "Produced using CDS Toolbox v1.0" | Trace of the tools/scripts used. Either this attribute or the "history" attribute needs to include information about the versioning of the software used to create the data. This is related with some of the EQC activities (WP4 of QA4SEAS). ISO 19115-2 defines a linage model where this is been considered. | |
| summary | The content will be provided ACDD (highly recommended): Text, defined phrase | A short paragraph describing the dataset | ||
| keywords | The content will be provided ACDD (highly recommended) : text, controlled vocabulary | A comma separated list of key words and phrases. | ||
| forecast_reference_time | SPECS: YYYY-MM-DDThh:mm:ssZ NOTE: This is ISO 8601:2004 extended format, but time zone is required to be UTC | "2011-06-01T00:00:00Z" | time of the analysis from which the forecast was made
| NOTE: This (note that works fine for SPECS data structure, i.e. one variable per start time per file) |
Spatial Coordinates
| Type (CMIP5) | Coordinate Name (CMIP5) | Dimension Names (CMIP5) | Axis | standard_name | long_name (CMIP5) | units (CF canonical units) | positive | valid_min (CMIP5) | valid_max (CMIP5) | bounds | Notes | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| double | lat | lat | Y | latitude | latitude | degrees_north | N/A | -90. | 90. | lat_bounds | Values (1x1deg grid) prescribed: [-90. , -89. , ..., 0., ... 90.] | |
| double | lon | lon | X | longitude | longitude | degrees_east | N/A | 0. | 360. | lon_bounds | Values (1x1deg grid) prescribed: dimension lon=360 [0. , 1. , ..., 358., 359.] | |
| double | plev | plev | Z | air_pressure | pressure | Pa | down | N/A | N/A | bounds? | This is also referred to as isobaric level by some tools [925., 850., 700., 500., 400., 300., 200., 100., 50., 30., 10.] | |
| double | depth | depth | Z | depth | depth | m | down | N/A | N/A | depth_bounds | Only used for soil model levels NOTE: Number and depth of levels is not prescribed by C3S | |
| double | height | height | Z | height | height | m | up or down | CMIP5: 2mtemp: 1. | CMIP5: 2mtemp: 10. | Used for single level fields (height, soil,SST) e.g. 2 m (for Temperature) | ||
C3S: string
| realization | str31=31 | E | realization | realization | 1 | N/A | N/A | N/A | members are not a physical quantity. Realization is a discrete coordinate and the | mebers it members its categorical values (ordered or non-ordered ones) SPECS approach: rXXiYYpZZ |
Time Coordinates
| Type | Coordinate Name | Dimension Names | Axis | standard_name | long_name | calendar | units | bounds | Notes | |
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| double | reftime | N/A | N/A | forecast_reference_time | "Start date of the forecast" | gregorian | UDUNITS time units e.g. "hours since YYYY-MM-DD hh:mm:ss TZhh:TZmm" | N/A | In SPECS it | wasis a "global_attribute" It has been additionally introduced here as a coordinate variable to ease future netCDF management (e.g. file merging) |
| double | leadtime | time | N/A | forecast_period | "Time elapsed since the start of the forecast" | N/A | SPECS: days | leadtime_bounds | The interval of time between the forecast reference time and the valid time Boundaries not needed when this time coordinate is used for instantaneous values (note that "time:point" is used as cell_method in those cases) | |
| double | time | time | N/A | time | "Verification time of the forecast" | gregorian | SPECS: "days since 1850-01-01" C3S: requested units can be relaxed to equivalent time units | time_bounds | Time for which the forecast is valid Boundaries not needed when this time coordinate is used for instantaneous values (note that "time:point" is used as cell_method in those cases) |
NOTE: Definitions for "leadtime" and "time" have been taken from SPECS. The introduction of "reftime" as a variable has been adapted from SPECS global attribute description for the forecast reference time.
NOTE: Even though there are different requested time steps among the variables (6h, 12h, 24h), just one set of time axes has been defined, as that would be enough when applying the requirement of "one variable per file"
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When the coordinate variables for a horizontal grid are longitude and latitude, a grid mapping variable with grid_mapping_name of latitude_longitude may be used to specify the ellipsoid and prime meridian. |
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Different name (e.g. CRS as in CF examples) |
Variables
NOTE: coordinates should list first of all the auxiliary coordinate(s) and then all the other coordinates.... SHOULD reftime, leadtime and realization be included as well????
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| Generic issues about attributes of data variables | |
| attribute(s) | Notes |
_FillValue missing_value
| should both of them be used? what values? |
| grid_mapping | name of grid_mapping variable |
| coordinates | include all the auxiliary coordinates, coordinates and dimensions |
Static Fields
| attributes | |||||||
| name (CMIP5) | dimensions | standard_name | long_name (CMIP5) | units | coordinates | grid_mapping | NOTES |
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| sftlf | lat,lon | land_area_fraction | "Land Area Fraction" | 1 | "lat lon"
| latitude_longitude | |
| orog | lat,lon | surface_altitude | "Surface Altitude" | m | "lat lon" | latitude_longitude | |
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