Introduction

(include an explanation about previous conventions.... SPECS, CF, ACDD)

Encoding Guide

Global attributes

The following properties are intended to provide information about where the data came from and what has been done to it. This information is mainly for the benefit of human readers and data discovery mechanisms. The attribute values are all character strings. When an attribute appears both globally and as a variable attribute, the variable’s version has precedence.

...

Attribute Name	Value	Examples	Comment
Conventions	CF convention string [Other convention] :...	"CF-1.6" "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	"world model v.0.1" "model-generated, GloSea5-GC2" "IPSL-CM5A-LR (2010) : atmos : LMDZ4 (LMDZ4_v5, 96x95x39); ocean : ORCA2 (NEMOV2_3, 2x2L31); seaIce : LIM2 (NEMOV2_3); ocnBgchem : PISCES (NEMOV2_3); land : ORCHIDEE (orchidee_1_9_4_AR5)"	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 http://copernicus-support.ecmwf.int CF: Free text	"http://copernicus-support.ecmwf.int"
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` SPECS conventions will be followed
comment	Free text	"Produced by University of Hamburg for DWD at ECMWF HPC facilities" "Run by CMCC at CINECA"	Miscellaneous information about the data, not captured elsewhere.
forecast_type	"forecast" or "hindcast"	"forecast"	To identify the type of data
history	Each line should begin with a timestamp indicating the date and time of day when the program was executed CF: Free Text	"Produced using CDS Toolbox on 1/6/2016" "Model raw output postprocessing with modelling environment (IMDI) at DKRZ: URL: http://svn-mad.zmaw.de/svn/mad/Model/IMDI/trunk, REV: 3436 2011-07-17T15:14:45Z CMOR rewrote data to comply with CF standards and CMIP5 requirements."	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. Well-behaved generic netCDF filters will automatically append their name and the parameters with which they were invoked to the global history attribute of an input netCDF file
commit, iso_lineage or lineage	Free text (ISO Lineage model 19115-2)	"Produced using CDS Toolbox v1.0"	trace of the tools/scripts used. Paco: include information about the versioning of the software used to create the data Antonio S. Cofino Gonzalez: We need a more implementtios examples on this. This could achiived in EQC WP where metadata is been part of their activities (i.e. WP4@QA4SEAS). ISO 19115-2 defines a linage model where this is been considered. TBD.
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

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)	Notes
double	lat	lat	Y	latitude	latitude	degrees_north	N/A	-90.	90.	Bounds required Values (1x1deg grid) prescribed: dimension lat=181 [-90. , -89. , ..., 0., ... 90.]
double	lon	lon	X	longitude	longitude	degrees_east	N/A	0.	360.	Bounds required Values (1x1deg grid) prescribed: dimension lon=360 [0. , 1. , ..., 358., 359.]
double	plev	plev	Z	air_pressure	pressure	Pa	down	N/A	N/A	This is also referred to as isobaric level by some tools Values prescribed: dimension plev=11 [925., 850., 700., 500., 400., 300., 200., 100., 50., 30., 10.] (NOTE: in hPa)
double	depth	depth	Z	depth	depth	m	down	N/A	N/A	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. 10mu/v: 1.	CMIP5: 2mtemp: 10. 10mu/v: 30.	Used for single level fields (height, soil,SST) e.g. 2 m (for Temperature)
C3S: string	realization	C3S: realization_dim CF: a different name is needed for dim/variable (see comment)	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 categorical values (ordered or non-ordered ones)

NOTE:

A dimension named "bounds" is also required for 'extensive' quantities.

Time Coordinates

Coordinate Name

Dimension Names

Axis

standard_name

long_name
(SPECS)

calendar

units

positive

Notes

leadtime

time

N/A

forecast_period

"Time elapsed since the start of the forecast"

N/A

SPECS: days
C3S: requested units can be relaxed to equivalent time units

N/A

The interval of time between the forecast reference time and the valid time

time

T

time

"Verification time of the forecast"

standard

SPECS: "days since 1850-01-01"

C3S: requested units can be relaxed to equivalent time units

N/A

Time for which the forecast is valid

NOTE: about forecast_reference_time as a global attribute (not generic, but SPECS use, as it will have one variable/start time per file)

...

Cell boundaries

...

Values

...

dimension bounds = 2

Maybe have "bounds" in a separate table/comment, explaining that they have the same units as the variable "bounded" by them. In addition to that I would find clearer if the time variable value is always at the end of the correspondent time_bounds as this works well both for instantaneous and accumulated/aggregated variables (e.g. time=20160922 06, timebounds = [20160922 00, 20160922 06])

for 24h freqs.

2 values with the same units as "time" coordinate
[0,24]

intervals must represent 24 hours

starting at 0Z
(is this a convention? WMO?)

...

As described in section 7.1 Cell Boundaries of CF convention.

Info

To represent cells we add the attribute bounds to the appropriate coordinate variable(s). The value of bounds is the name of the variable that contains the vertices of the cell boundaries. We refer to this type of variable as a "boundary variable." A boundary variable will have one more dimension than its associated coordinate or auxiliary coordinate variable. The additional dimension should be the most rapidly varying one, and its size is the maximum number of cell vertices. Since a boundary variable is considered to be part of a coordinate variable’s metadata, it is not necessary to provide it with attributes such as long_name and units

Bounds Name	Dimensions	Comments
time_bounds	time,bounds	where to put the time coordinate (beginning, middle, end of the bounds) ? e.g. time=20160922 06 timebounds = [20160922 00, 20160922 06] for 24h time steps: [0,24] is that convention always valid?
lat_bounds	lat, bounds	Values (1x1deg grid) prescribed: [-90., 89.], [-89., -88.], ... [89., 90.]
lon_bounds	lon, bounds	Values (1x1deg grid) prescribed: [0., 1.], [1., 2.], ... [359., 360.]
depth_bounds	depth,bounds	Should define the full vertical extent of the soil model layers

Variables

NOTE: coordinates should list first of all the auxiliary coordinate(s) and then all the other coordinates

Static Fields

attributes

name
(CMIP5)

dimensions

standard_name

long_name

units

coordinates

cell_methods

grid_mapping

NOTES

lat,lon

land_area_fraction

1

"lat lon"

lat,lon

surface_altitude

m

"lat lon"

Surface Fields (defined at a given height level)

NOTE: about bounds, time_bounds etc. in the context of SPECS (i.e. one variable per file)

attributes

name
(CMIP5)

dimensions

standard_name

long_name

units

coordinates

cell_methods

grid_mapping

NOTES

tas

time,lat,lon

air_temperature

K

"height time lat lon"

"time: point"

C3S: required
CF: recommended

tasmax

time,lat,lon

air_temperature

K

"height time lat lon"

"time: maximum (interval: value unit)"

C3S: required.
CF: interval is optional

Ensemble coordinate

TBD

Pressure level coordinates

These are specified as being:

925, 850, 700, 500, 400, 300, 200, 100, 50, 30 and 10 hPa

Invariant Fields

...

step

...

name

...

land_area_fraction

...

Surface Fields (defined at a given height level)

Finalised

Priority

(i.e. should be defined first for MARS)

requested variables
(ITT table)C3S NetCDF Convention

step

Parameter Identifier )
Originating Centre

name

name
(CMIP5)standard_nameunitsdimensionsCell MethodsCoordinates

Coordinate

Bounds

commentsY16 h inst167982m temperaturetasair_temperatureKtime,lat,lon "time: point"
CF: recommended
C3S: required

"height"

C3S: Just 2m and 1.5m will be valid values for the height coordinate of this variable

CF: If the variable is instantaneous it shouldn't have time_bounds

Y124 h inst.5198max 2m temperature (last 24h)tasmaxair_temperatureKtime,lat,lon

"time: maximum (interval: value unit)"

CF: interval is optional

C3S: interval is required. (Units in UDUNITS)

"height"

time_boundsC3S: Just 2m and 1.5m will be valid values for the height coordinate of this variable

C3S: The interval is required to have a value<=3 hours)

Y124 h inst.5298min 2m temperature (last 24h)tasmin

tasmin

time,lat,lon

air_temperature

K

"height time

,

lat

,

lon"

"time:

maximum

minimum (interval: value unit)"

CF: interval is optional

C3S:

interval is

required.

(Units in UDUNITS)"height"

CF: interval is optional

C3S:

Just 2m and 1.5m will be valid values for the height coordinate of this variableC3S:

The interval is required to have a value<=3 hours)

N26 h inst168982m dewpoint temperature

dew_point_temperature

K

K	scalar value=2 unit=

m

MetOffice's temperatures are at 1.5m

N2

6 h

inst

1659810m U wind component

m
		x_wind		m s-1

scalar

value=10

unit=m

N2

6 h

inst

1669810m V wind component


		y_wind		m s-1

scalar

value=10

unit=m

N224 h inst4998

10m max wind gust

wind_speed

m s-1

scalar

value=10

unit=m

...

Surface Fields (not defined at a height level)

...

Antonio S. Cofino Gonzalez: discussion on multi-time dimension data

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Key

Table of Contents

Introduction

Encoding Guide

Global attributes

Spatial Coordinates

NOTE:

Time Coordinates

Cell boundaries

Variables

Static Fields

Surface Fields (defined at a given height level)

Ensemble coordinate

Pressure level coordinates

Invariant Fields

Surface Fields (defined at a given height level)

Surface Fields (not defined at a height level)

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Versions Compared

Old Version 9

New Version 10

Key

Table of Contents

Introduction

Encoding Guide

Global attributes

Spatial Coordinates

NOTE:

Time Coordinates

Cell boundaries

Variables

Static Fields

Surface Fields (defined at a given height level)

Ensemble coordinate

Pressure level coordinates

Invariant Fields

Surface Fields (defined at a given height level)

Surface Fields (not defined at a height level)