Introduction

During these first stages of the proof-of-concept phase of C3S seasonal forecast activity, we have been working in standardise to define a standard for the data provision in netCDF. This standard is described below.

The proposal is constrained by the CF convention, and we have also tried not to diverge from specifications coming from other well established communities: SPECS and CMIP5/6

Additionally ACDD has been also taken into account when defining the data discovery related metadata.

In that senseHence, the following links are valuable sources of information that have informed the definition of this proposal:

...

SPECS file content and format, data structure and metadata

CMIP5 list of variables

CMIP6 Data Request: MIP variables search

ACDD convention

Examples

Some example files have been created following the guidelines contained in this document.

View file

name	ncfiles.tgz
height	150

Encoding Guide for netCDF files conforming to C3S-0.1

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, it is the variable’s version which has precedence.

Attribute Name	Value	Examples	Comment
Conventions	CF_convention string [_string C3S-0.1 [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"<short institution name> seasonal forecast model output prepared for C3S" CF: Free text ACDD (highly recommended)	"IPSL-CM5A-LR ECMWF seasonal forecast model output prepared for CMIP5 RCP4.5C3S"	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 <short institution name> is the first element of the comma-separated list of values of the corresponding "institution" attribute
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 A way of labelling hindcasts and forecasts to match them needs to be devised.
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. 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 Introduced as global attribute to keep compatibility with SPECS NOTE: This works fine for SPECS data structure, i.e. one variable per start time per file

Spatial Coordinates

...

Values (1x1deg grid) prescribed:
dimension lat=181

[-90. , -89. , ..., 0., ... 90.]

...

[0. , 1. , ..., 358., 359.]

...

Pa

...

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: values here written in hPa, they should be Pa)

...

m

...

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

...

C3S: realization_dim

CF: a different name is needed for dim/variable
(see comment)

...

Time Coordinates

...

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

...

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

...

time

...

SPECS: "days since 1850-01-01"

C3S: requested units can be relaxed to equivalent time units

...

Time for which the forecast is valid

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"

Cell boundaries

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

...

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?

...

Values (1x1deg grid) prescribed:

[0., 1.], [1., 2.], ... [359., 360.]

...

The following template should be followed in constructing this string: '<model_id> : atmosphere: <model_name> (<technical_name>, <resolution_and_levels>); ocean: <model_name> (<technical_name>, <resolution_and_levels>); sea ice: <model_name> (<technical_name>); land: <model_name> (<technical_name>)'' Additional explanatory information may follow the required information. NOTE that for some models, it may not make much sense to include all these components. The first portion of the string, “model_id”, should be built using the following template: "model_name-vYYYYMMDD" where YYYYMMDD is the release date of that version of the model (the date when it was first used)	"System4-v20111101: atmos: IFS (CY36R4, TL255L91); ocean: NEMOv3.0 (ORCA1_z42, 1x1L42); Local modifications in NEMOv3.0 (dynamic memory, flexible output, surface flux forcing, closure of frewsh water budget). FLAKE lake model "	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. It is a character string fully identifying the model and version used to generate the output. It should include information concerning the component models. Note that information about changes in the individual components respect to the "official" releases should be included (e.g. a different bathymetry) The "source" attribute should include as much information as possible to not just identify the model but to brief the user about it
institute_id	Controlled Vocabulary: "ecmf" for ECMWF "egrr" for Met Office "lfpw" for Météo-France "edzw" for DWD "cmcc" for CMCC	"edzw"	Standardized 4 characters identifier of the institution that produced the data; NOTE all the values come from abbreviations of WMO/GRIB "originating centre" table, except CMCC (not available there)
institution	Controlled Vocabulary: "ECMWF, European Centre for Medium-Range Weather Forecasts, Reading, United Kingdom" "Met Office, Exeter, United Kingdom" "Météo-France, Toulouse, France" "DWD, Deutscher Wetterdienst, Offenbach, Germany" "CMCC, Centro Euro-Mediterraneo sui Cambiamenti Climatici, Bologna, Italy" CF: Free text	"Météo-France, Toulouse, France"	Specifies where the original data was produced. The name of the institution principally responsible for originating this data. NOTE: The first element of the comma-separated list of values will be used as a shortened version of this attribute in some of the other global attributes ('summary', 'title')
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". The name "creation_date" has been used following SPECS convention.
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	Controlled Vocabulary "forecast" or "hindcast"	"forecast"	To identify the type of data
modeling_realm	Controlled Vocabullary "atmos", "ocean", "land", "landIce", "seaIce", "aerosol", "atmosChem", "ocnBgchem"	"seaIce"	A string that indicates the high-level modelling component that is particularly relevant to the variable encoded Controlled vocabulary taken from SPECS Value depends on the variable (see "global attributes" column in variables tables)
frequency	Controlled Vocabulary "mon", "day", "12hr", "6hr", "fix"	"day"	A string indicating the interval between individual time-samples. Controlled vocabulary taken from SPECS (extended to include "12hr" data) Value depends on the variable (see "global attributes" column in variables tables)
level_type	Controlled Vocabulary "surface", "pressure", "soil"	"pressure"	A string indicating the type of the level where the variable comes from Value depends on the variable (see "global attributes" column in variables tables)
history	Empty string	""	To avoid this attribute being polluted by usual netCDF tools, it must be enforced to an empty string.
commit	timestamp + URL of a commit in a CVS repository	"2017-04-01T13:48:25Z https://software.ecmwf.int/stash/projects/C3SS/repos/ecmf/System4_v20111101"	This attribute intends to keep trace of the tools/scripts used to post-process the data output from the model. Ideally it should contain the link to a repository containing the specific set of tools and scripts needed to reproduce the same data from the model output. It is highly desirable to have that traceability information. As a surrogate when the previous is not feasible it should include the timestamp followed by an URL pointing to the C3S documentation repository of the correspondent model version (properly labelled with the <model_id> introduced in 'source" attribute)
summary	Controlled Vocabulary: "Seasonal Forecast data produced by <short institution name> as its contribution to the seasonal forecast activity of the Copernicus Climate Change Service (C3S). The data has global coverage with a 1-degree horizontal resolution and spans for around 6 months since the start date" ACDD (highly recommended)	"Seasonal Forecast data produced by DWD as its contribution to the seasonal forecast activity of the Copernicus Climate Change Service (C3S). The data has global coverage with a 1-degree horizontal resolution and spans for around 6 months since the start date"	A short paragraph describing the dataset <short institution name> is the first element of the comma-separated list of values of the corresponding "institution" attribute
keywords	Fixed string "Seasonal Forecasts, C3S, ECMWF, Copernicus, Climate Change, Climate Services, Earth Science Services, Environmental Advisories, Climate Advisories" ACDD (highly recommended)		A comma separated list of key words and phrases. NOTE: This attribute is likely to be modified in the future, once the contents of the Thesaurus for CDS faceting will be defined
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 Introduced as global attribute to keep compatibility with SPECS (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_bnds	Values (1x1deg grid) prescribed: center of 1-degree cells dimension lat=180 [-89.5, -88.5 , ..., -0.5, 0.5 ... 89.5]
double	lon	lon	X	longitude	longitude	degrees_east	N/A	0.	360.	lon_bnds	Values (1x1deg grid) prescribed: center of 1-degree cells dimension lon=360 [0.5 , 1.5 , ..., 358.5, 359.5]
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: values here written in hPa, they should be Pa)
double	plev	plev	Z	air_pressure	pressure	Pa	down	N/A	N/A
double	depth	depth	Z	depth	depth	m	down	N/A	N/A	depth_bnds	Only used for soil model levels NOTE: Number and depth of levels is not prescribed by C3S
double	height	(scalar auxiliary coordinate)	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	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 members its categorical values (ordered or non-ordered ones) SPECS approach: rXXiYYpZZ

NOTE about the horizontal coordinates: The regridding procedure to provide the data in the 1-degree grid must take into account that the full definition of the gird cells is given by the cell boundaries (lat_bnds, lon_bnds)

Time Coordinates

Type

Coordinate Name

Dimension Names

Axis

standard_name

long_name

calendar

units

bounds

Notes

double

reftime

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 is only given as a "global_attribute"
It has been additionally introduced here as a coordinate variable to ease future netCDF management (e.g. file merging)

double

leadtime

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

leadtime_bnds

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)

When boundaries are required, the value of the coordinate must be in the centre of the correspondent time cell boundaries

double

time

leadtime

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_bnds

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)

When boundaries are required, the value of the coordinate must be in the centre of the correspondent time cell boundaries

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"

Warning

"leadtime" has been selected as dimension (instead of "time") for both time and leadtime. That means "leadtime" is the coordinate and "time" is an auxiliary coordinate

This diverges from SPECS (where "time" was the name of the dimension and the coordinate, and "leadtime" was an auxiliary coordinate)
Here it has been done like that because
1. both reftime and leadtime are the relevant (let's say "orthogonal") coordinates coming from the relationship time = reftime + leadtime
2. doing like that has some advantages when merging netCDF files ("leadtime" can be easily shared by different variables in a merged file, while "time" cannot)

Cell boundaries

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_bnds	leadtime, bnds
leadtime_bnds	leadtime, bnds
lat_bnds	lat, bnds	Values (1x1deg grid) prescribed: [-90., -89.], [-89., -88.], ... [89., 90.]
lon_bnds	lon, bnds	Values (1x1deg grid) prescribed: [0., 1.], [1., 2.], ... [359., 360.]
depth_bnds	depth, bnds	Should define the full vertical extent of the soil model layers

Grid mapping

Info

As described in section 5.6 Grid Mappings and Projections of CF convention. (see quote below)

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.

Following that, it has been decided to include, as mandatory, in this C3S netcdf encoding guide the following variable

Code Block
char hcrs ; hcrs:grid_mapping_name = "latitude_longitude" ;

Variables

Common attributes

The following attributes must be included in all the variables:

attribute name	value	comment
grid_mapping	hcrs

Conditional attributes

The following attributes may be included in the attribute list for a given variable if the conditions specified are fulfilled:

attribute name	value	comment
_FillValue	Set by netCDF library	Those attributes must be included ONLY when the variable has missing values. If they are NOT present in the actual data field values, they should NOT be included as variable attributes.
missing_value	Set by netCDF library

Candidate attributes

The following attributes may be included in the attribute list for a given variable at a later date as this standard evolves:

attribute name	value	comment
valid_max	TBD	see below
valid_min	TBD	see below

Info

title	valid range attributes

Both "valid_min" and "valid_max" attributes should be included as variable attributes, but a set of sensible values for each and every variable needs to be provided.

In the meantime, it is proposed not to include them and just bear in mind that they will be required to be introduced at some point in the future.

Static Fields

attributes

name
(CMIP5)

dimensions

standard_name

long_name
(CMIP5)

units

coordinates

valid_min

valid_max

global attributes

sftlf

lat,lon

land_area_fraction

"Land Area Fraction"

1

"lat lon"

0

1

"frequency":"fix"
"level_type": "surface"
"modeling_realm":"atmos"

orog

lat,lon

surface_altitude

"Surface Altitude"

m

"lat lon"

"frequency":"fix"
"level_type": "surface"
"modeling_realm":"atmos"

Surface Fields (defined at a given height level)

name (CMIP5/6&C3S)	dimensions	standard_name	long_name (CMIP5/6&C3S)	units	coordinates	cell_methods	global attributes	NOTES
		attributes
tas	leadtime,lat,lon	air_temperature	"Near-Surface Air Temperature"	K	"reftime realization time leadtime height lat lon"	"leadtime: point" C3S: required CF: recommended	"frequency":"6hr" "level_type": "surface" "modeling_realm":"atmos"	height is usually 2m height:valid_min = 1.; height:valid_max = 10. ;
tasmax	leadtime,lat,lon	air_temperature	"Daily Maximum Near-Surface Air Temperature"	K	"reftime realization time leadtime height lat lon"	"leadtime: maximum (interval: <value> <unit>)" C3S: interval is required. CF: interval is optional	"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	height is usually 2m height:valid_min = 1.; height:valid_max = 10. ; C3S: The interval is required to have a value<=3 hours) leadtime_bnds, time_bnds are required
tasmin	leadtime,lat,lon	air_temperature	"Daily Minimum Near-Surface Air Temperature"	K	"reftime realization time leadtime height lat lon"	"leadtime: minimum (interval: <value> <unit>)" C3S: interval is required. CF: interval is optional	"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	height is usually 2m height:valid_min = 1.; height:valid_max = 10. ; C3S: The interval is required to have a value<=3 hours) leadtime_bnds, time_bnds are required
tdps	leadtime,lat,lon	dew_point_temperature	"2m Dewpoint Temperature"	K	"reftime realization time leadtime height lat lon"	"leadtime: point" C3S: required CF: recommended	"frequency":"6hr" "level_type": "surface" "modeling_realm":"atmos"	height is usually 2m height:valid_min = 1.; height:valid_max = 10. ;
uas	leadtime,lat,lon	x_wind	Eastward Near-Surface Wind	m s-1	"reftime realization time leadtime height lat lon"	"leadtime: point" C3S: required CF: recommended	"frequency":"6hr" "level_type": "surface" "modeling_realm":"atmos"	height is usually 10m height:valid_min = 1.; height:valid_max = 30. ;
vas	leadtime,lat,lon	y_wind	Northward Near-Surface Wind	m s-1	"reftime realization time leadtime height lat lon"	"lead

Grid mapping

As described in section 5.6 Grid Mappings and Projections of CF convention.

Info
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.

Code Block
char latitude_longitude ; latitude_longitude:grid_mapping_name = "latitude_longitude" ;

NOTE: Wouldn't a different name be more appropriate? (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????

NOTE: type double/real????

Static Fields

...

"lat lon"

...

Surface Fields (defined at a given height level)

attributes name
(CMIP5)dimensionsstandard_namelong_name
(CMIP5)unitscoordinatescell_methodsgrid_mappingNOTEStastime,lat,lonair_temperature"Near-Surface Air Temperature"K

"height time lat lon"

"

time: point"

C3S: required
CF: recommended

latitude_longitude

height is usually 2m

tasmaxtime,lat,lonair_temperature"Daily Maximum Near-Surface Air Temperature"K

"height time lat lon"

"time: maximum (interval: <value> <unit>)"

C3S: required.
CF: interval is optional

latitude_longitude

height is usually 2m

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

"frequency":"6hr"
"level_type": "surface"
"modeling_realm":"atmos"

height is usually 10m

height:valid_min = 1.;
height:valid_max = 30. ;

wsgmax

N/A in CMIP

leadtime,lat,lon

wind_speed_of_gust

"Maximum Wind Speed of Gust"

N/A in CMIP

m s-1

"reftime realization time leadtime height lat lon"

"leadtime: maximum

tasmintime,lat,lonair_temperature"Daily Minimum Near-Surface Air Temperature"K

"height time lat lon"

"time: minimum

(interval: <value> <unit>)"

C3S: interval is required.
CF: interval is optional

latitude_longitude

"frequency":"day"
"level_type": "surface"
"modeling_realm":"atmos"

height is usually 10m

height:valid_min = 1.;
height:valid_max = 30. ;

height is usually 2m

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

time,lat,londew_point_temperature K"height time lat lon""time: point"
C3S: required
CF: recommended latitude_longitude

height is usually 2m

uastime,lat,lon

leadtime_bnds, time_bnds are required

Surface Fields (not defined at a height level)

name (CMIP5/6&C3S)	dimensions	standard_name	long_name (CMIP5/6&C3S)	units	coordinates	cell_methods	valid_min	valid_max	global attributes	Comments
		attributes
psl	leadtime,lat,lon	air_pressure_at_sea_level	"Sea Level Pressure"	Pa	"reftime realization time leadtime lat lon"	"lead

x_windEastward Near-Surface Windm s-1"height time lat lon""time: point"
C3S: required
CF: recommended latitude_longitude

height is usually 10m

vastime,lat,lony_windNorthward Near-Surface Windm s-1"height time lat lon""

time: point"

C3S: required
CF: recommended

latitude_longitude

height is usually 10m

		"frequency":"6hr" "level_type": "surface" "modeling_realm":"atmos"
clt	leadtime

time

,lat,lon

wind

cloud_

speedm s-

area_

of_gust

fraction

"Total Cloud Fraction"

1

"

height

reftime realization time leadtime lat lon"

"time: maximum (interval: <value> <unit>)

"leadtime: point"

C3S: required

.

CF:

interval is optional latitude_longitude

height is usually 10m

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

Surface Fields (not defined at a height level)

recommended			"frequency":"6hr" "level_type": "surface" "modeling_realm":"atmos"
tsl	leadtime,lat,lon	soil_temperature	"Temperature of Soil"	K	"reftime realization time leadtime lat lon"	"leadtime: point" C3S: required CF: recommended	"frequency":"6hr" "level_type": "surface" "modeling_realm":"land"
tso	leadtime,lat,lon	sea_surface_temperature	"Sea Surface Temperature"	K	"reftime realization time leadtime lat lon"	"lead

attributes name
(CMIP5)dimensionsstandard_namelong_name
(CMIP5)unitscoordinatescell_methodsgrid_mappingNOTESpsltime,lat,lonair_pressure_at_sea_level"Sea Level Pressure"Pa "

time: point"

C3S: required
CF: recommended

latitude_longitude clttime,lat,loncloud_area_fraction"Total Cloud Fraction"1 "time: point"
C3S: required
CF: recommended
latitude_longitude

"frequency":"6hr"
"level_type": "surface"
"modeling_realm":"ocean"

sitemptop

N/A in CMIP

leadtime

tsltime

,lat,lon

soil

sea_ice_temperature

"Surface Temperature of

Soil"

Sea Ice"

N/A in CMIP

K

"reftime realization time leadtime lat lon"

"leadtime: point"

C3S: required
CF: recommended

latitude_longitude tso

		"frequency":"6hr" "level_type": "surface" "modeling_realm":"seaIce"
sic	leadtime

time

,lat,lon

sea_ice_

surface

area_

temperature

fraction

"Sea

Surface Temperature

Ice Area Fraction"

K

1	"reftime realization time leadtime lat lon"

"leadtime: point"

C3S: required
CF: recommended

latitude_longitude time,lat,lonsea_ice_temperature K

"frequency":"day"
"level_type": "surface"
"modeling_realm":"seaIce"

mrlsl

leadtime,depth,lat,lon

moisture_content_of_soil_layer

"Water Content per Unit Area of Soil Layers"

kg m^-2

"reftime realization time leadtime depth lat lon"

"lead

"

time: point"

C3S: required
CF: recommended

latitude_longitude sic

"frequency":"day"
"level_type": "soil"
"modeling_realm":"land"

lwesnw

N/A in CMIP

leadtime

time

,lat,lon

sea_ice_area_fraction"Sea Ice Area Fraction"1

lwe_thickness_of_surface_snow_amount

"Liquid Water Equivalent Thickness of Surface Snow Amount"

N/A in CMIP

m

"reftime realization time leadtime lat lon"

"lead

"

time: point"

C3S: required
CF: recommended

latitude_longitude

"frequency":"day"
"level_type": "surface"
"modeling_realm":"land"

rhosn

N/A in CMIP

leadtime,

time,depth,

lat,lon

mass_content_of_water_in_soil_layer

snow_density

"Snow Density"

N/A in CMIP

kg m^-

2

³	"reftime realization time leadtime lat lon"

"leadtime: point"

C3S: required
CF: recommended

latitude_longitude

"frequency":"day"
"level_type": "surface"
"modeling_realm":"land"

lweprs

N/A in CMIP

leadtime

time

,lat,lon

lwe_thickness_of_

surface

stratiform_

snow

precipitation_amount

m "time: point"
C3S: required
CF: recommended
latitude_longitude

"Liquid Water Equivalent Thickness of Stratiform Precipitation Amount"

N/A in CMIP

m

"reftime realization time leadtime lat lon"

"leadtime: sum"

"frequency":"day"
"level_type": "surface"
"modeling_realm":"atmos"

leadtime_bnds, time_bnds are required

lweprc

N/A in CMIP

leadtime

time,lat,lonsnow_density kg m^-3 "time: point"
C3S: required
CF: recommended
latitude_longitude time

,lat,lon

lwe_thickness_of_

stratiform

convective_precipitation_amount

"Liquid Water Equivalent Thickness of Convective Precipitation Amount"

N/A in CMIP

m

"reftime realization time leadtime lat lon"

"leadtime: sum"

C3S: required
CF: recommended
latitude_longitude

"frequency":"day"
"level_type": "surface"
"modeling_realm":"atmos"

leadtime_bnds, time_bnds are required

lwepr

N/A in CMIP

leadtime

time

,lat,lon

lwe_thickness_of_

convective_

precipitation_amount

"Liquid Water Equivalent Thickness of Total Precipitation Amount"

N/A in CMIP

m

"reftime realization time leadtime lat lon"

"leadtime: sum"

C3S: required
CF: recommended
latitude_longitude

"frequency":"day"
"level_type": "surface"
"modeling_realm":"atmos"

leadtime_bnds, time_bnds are required

lweprsn

N/A in CMIP

leadtime

time

,lat,lon

lwe_thickness_of_

precipitation

snowfall_amount

"Liquid Water Equivalent Thickness of Snowfall Amount"

N/A in CMIP

m

"reftime realization time leadtime lat lon"

"leadtime: sum"

C3S: required
CF: recommended
latitude_longitude

		"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	leadtime_bnds, time_bnds are required
hfss	leadtime

time

,lat,lon

lwe

surface_

thickness

upward_

of

sensible_

snowfall

heat_

amount m

flux

"Surface Upward Sensible Heat Flux"

W m^-2

"reftime realization time leadtime lat lon"

"leadtime: mean (interval: <value> <unit>)

"time: sum

"

C3S: interval is required

.
CF

: recommended
latitude_longitude

: interval is optional			"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	leadtime_bnds, time_bnds are required
hfls	leadtime

time

,lat,lon

integral_of_

surface_

downward

upward_

sensible

latent_heat_

of_

flux

_wrt_time

"Surface Upward Latent Heat Flux"

W

s

m^-2

"time: sum"
C3S: required
CF: recommended
latitude_longitudeinstantaneous, instead of integral?
does it works with SW rad???
would it work with "instantaneous" 24h mean?

"reftime realization time leadtime lat lon"	"leadtime: mean (interval: <value> <unit>)" C3S: interval is required. CF: interval is optional			"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	leadtime_bnds, time_bnds are required
rsds	leadtime

time

,lat,lon

integral_of_

surface_

downward

downwelling_

latent_heat

shortwave_

of_

flux_

wrt_time

in_air

"Surface Downwelling Shortwave Radiation"

W

W s

m^-2

"reftime realization time leadtime lat lon"

"leadtime: mean (interval: <value> <unit>)

"time: sum

"

C3S: interval is required

.
CF

: recommended

: interval is optional			"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	leadtime_bnds, time_bnds are required
rlds	leadtime

latitude_longitude time

,lat,lon

integral_of_

surface_downwelling_

shortwave

longwave_flux_in_air

_wrt_time

"Surface Downwelling Longwave Radiation"

W

s

m^-2

"reftime realization time leadtime lat lon"

"leadtime: mean (interval: <value> <unit>)

"time: sum

"

C3S: interval is required

.
CF

: recommended

: interval is optional			"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	leadtime_bnds, time_bnds are required
rss	leadtime

latitude_longitude time

,lat,lon

integral_of_

surface_net_downward_shortwave_flux

_wrt_time

"Net Shortwave Surface Radiation"

W

s

m^-2

"reftime realization time leadtime lat lon"

"leadtime: mean (interval: <value> <unit>)

"time: sum

"

C3S: interval is required

.
CF

: recommended

: interval is optional			"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	leadtime_bnds, time_bnds are required
rls	leadtime

latitude_longitude time

,lat,lon

integral_of_

surface_net_downward_longwave_flux

_wrt_time

"Net Longwave Surface Radiation"

W

s

m^-2

"reftime realization time leadtime lat lon"

"leadtime: mean (interval: <value> <unit>)

"time: sum

"

C3S:

required
CF: recommended

interval is required.
CF: interval is optional

"frequency":"day"
"level_type": "surface"
"modeling_realm":"atmos"

leadtime_bnds, time_bnds are required

rst

N/A in CMIP

leadtime

latitude_longitude time

,lat,lon

integral_of_ W s m^-2 "time: sum"
C3S: required
CF: recommended
latitude_longitude time,lat,lonintegral_of_

toa_net_downward_shortwave_flux

_wrt_time

"TOA Net Shortwave Radiation"

N/A in CMIP

W m^-2

"reftime realization time leadtime lat lon"

"leadtime: mean (interval: <value> <unit>)"

C3S: interval is required.
CF: interval is optional

"frequency":"day"
"level_type": "surface"
"modeling_realm":"atmos"

leadtime_bnds, time_bnds are required

rlt

N/A in CMIP

leadtime,lat,lon

toa_net_downward_longwave_flux

_wrt_time

"TOA Net Longwave Radiation"

N/A in CMIP

W

W s

m^-2

"reftime realization time leadtime lat lon"

"leadtime: mean (interval: <value> <unit>)

"time: sum

"

C3S:

required

interval is r equired.

CF

: recommended

: interval is optional			"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	leadtime_bnds, time_bnds are required
rsdt	leadtime

latitude_longitude time

,lat,lon

integral_of_

toa_incoming_shortwave_flux

_wrt_time

"TOA Incident Shortwave Radiation"

W

s

m^-2

"reftime realization time leadtime lat lon"

"leadtime: mean (interval: <value> <unit>)

"time: sum

"

C3S: interval is required

.
CF:

recommended

interval is optional			"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	leadtime_bnds, time_bnds are required
tauu	leadtime

latitude_longitude time

,lat,lon

integral_of_

surface_downward_eastward_stress

_wrt_time

"Surface Downward Eastward Wind Stress"

Pa

s

"reftime realization time leadtime lat lon"

"leadtime: mean (interval: <value> <unit>)

"time: sum

"

C3S: interval is required

.
CF

: recommended

: interval is optional			"frequency":"day" "level_type": "surface" "modeling_realm":"atmos"	leadtime_bnds, time_bnds are required
tauv	leadtime

latitude_longitude time

,lat,lon

integral_of_

surface_downward_northward_stress

_wrt_time

"Surface Downward Northward Wind Stress"

Pa

s

"reftime realization time leadtime lat lon"

"leadtime: mean (interval: <value> <unit>)

"time: sum

"

C3S:

required
CF: recommended

interval is required.
CF: interval is optional

"frequency":"day"
"level_type": "surface"
"modeling_realm":"atmos"

leadtime_bnds, time_bnds are required

lwee

N/A in CMIP

leadtime

latitude_longitude time

,lat,lon

lwe_thickness_of_water_evaporation_amount

"Liquid Water Equivalent Thickness of Evaporation Amount"

N/A in CMIP

m

"reftime realization time leadtime lat lon"

"leadtime: sum"

"frequency":"day"
"level_type": "surface"
"modeling_realm":"land"

leadtime_bnds, time_bnds are required

mrroa

N/A in CMIP

leadtime

m "time: sum"
C3S: required
CF: recommended
latitude_longitude time

,lat,lon

runoff_amount

"Total Run-off Amount"

N/A in CMIP

kg m^-2

"reftime realization time leadtime lat lon"

"leadtime: sum"

"frequency":"day"

C3S: required
CF: recommended
latitude_longitude

"level_type": "surface"
"modeling_realm":"land"

leadtime_bnds, time_bnds are required

mrroas

N/A in CMIP

leadtime

time

,lat,lon

surface_runoff_amount

"Surface Run-off Amount"

N/A in CMIP

kg m^-2

"reftime realization time leadtime lat lon"

"leadtime: sum"

"frequency":"

C3S: required
CF: recommended

day"
"level_type": "surface"
"modeling_realm":"land"

leadtime_bnds, time_bnds are required

mrroab

N/A in CMIP

leadtime

latitude_longitude time

,lat,lon

subsurface_runoff_amount

"Subsurface Run-off Amount"

N/A in CMIP

kg m^-2

"reftime realization time leadtime lat lon"

"leadtime: sum"

"frequency":"day"

C3S: required
CF: recommended
latitude_longitude

Pressure Level Fields

"level_type": "surface"
"modeling_realm":"land"

leadtime_bnds, time_bnds are required

Pressure Level Fields

"time: point"
C3S: required
CF: recommended

name (CMIP5)	dimensions	standard_name	long_name (CMIP5)	units	coordinates	cell_methods	grid_mapping	NOTES	valid_min	valid_max	global attributes
		attributes
		attributes
zg	leadtime		time,plev,lat,lon	geopotential		m² s^-2		latitude_longitude		_height	"Geopotential Height"	m	"reftime realization time leadtime plev lat lon"	"leadtime: point" C3S: required CF: recommended		"frequency":"12hr" "level_type": "pressure" "modeling_realm":"atmos"
ta	leadtime	ta	time,plev,lat,lon	air_temperature	"Air Temperature"	K	"reftime realization time leadtime plev lat lon"	"leadtime: point" C3S: required CF: recommended	latitude_longitude			"frequency":"12hr" "level_type": "pressure" "modeling_realm":"atmos"
hus	timeleadtime,plev,lat,lon	specific_humidity	"Specific Humidity"	1	"reftime realization time leadtime plev lat lon"	"leadtime: point" C3S: required CF: recommended	latitude_longitude				"frequency":"12hr" "level_type": "pressure" "modeling_realm":"atmos"
rv N/A in CMIP	leadtime		time,plev,lat,lon	atmosphere_relative_vorticity	"Relative Vorticity" N/A in CMIP	s^-1	"reftime realization time leadtime plev lat lon"	"leadtime: point" C3S: required CF: recommended	latitude_longitude						"frequency":"12hr" "level_type": "pressure" "modeling_realm":"atmos"
wnddiv N/A in CMIP	leadtimetime,plev,lat,lon	divergence_of_wind	"Divergence of Wind" N/A in CMIP	s^-1	"reftime realization time leadtime plev lat lon"	"leadtime: point" C3S: required CF: recommended	latitude_longitude				"frequency":"12hr" "level_type": "pressure" "modeling_realm":"atmos"
ua	timeleadtime,plev,lat,lon	x_wind	"Eastward Wind"	m s^-1	¹	"reftime realization time leadtime plev lat lon"	"leadtime: point" C3S: required CF: recommended	latitude_longitude			"frequency":"12hr" "level_type": "pressure" "modeling_realm":"atmos"
va	timeleadtime,plev,lat,lon	y_wind	"Northward Wind"	m s^-1	"reftime realization time leadtime plev lat lon"	"leadtime: point" C3S: required CF: recommended	latitude_longitude

...

"frequency":"12hr"
"level_type": "pressure"
"modeling_realm":"atmos"

Space shortcuts

Page tree

Versions Compared

Old Version 28

New Version Current

Key

Introduction

Examples

Encoding Guide for netCDF files conforming to C3S-0.1

Global attributes

Spatial Coordinates

Time Coordinates

Cell boundaries

Spatial Coordinates

Time Coordinates

Cell boundaries

Grid mapping

Variables

Common attributes

Conditional attributes

Candidate attributes

Static Fields

Surface Fields (defined at a given height level)

Grid mapping

Variables

Static Fields

Surface Fields (defined at a given height level)

Surface Fields (not defined at a height level)

Surface Fields (not defined at a height level)

Pressure Level Fields

Pressure Level Fields

Space shortcuts

Page tree

Page History

Versions Compared

Old Version 28

New Version Current

Key

Introduction

Examples

Encoding Guide for netCDF files conforming to C3S-0.1

Global attributes

Spatial Coordinates

Time Coordinates

Cell boundaries

Spatial Coordinates

Time Coordinates

Cell boundaries

Grid mapping

Variables

Common attributes

Conditional attributes

Candidate attributes

Static Fields

Surface Fields (defined at a given height level)

Grid mapping

Variables

Static Fields

Surface Fields (defined at a given height level)

Surface Fields (not defined at a height level)

Surface Fields (not defined at a height level)

Pressure Level Fields

Pressure Level Fields