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Warning
titleWARNING

Some modifications have been made in this page since the meeting at C3S General Assembly at Toulouse
More details about those changes, and the final netCDF examples following the guide are expected to be made available around the 21st April 2017

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:

...

CMIP6 Data Request: MIP variables search

ACDD convention

 

...

titleNOTES about tables color coding

Along this document some issues are still at some level under discussion. To mark that it has been followed the following color coding scheme

Examples

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

 

View file
namencfiles.tgz
height150

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. 


To identify the type of data

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)
Attribute NameValueExamplesComment
ConventionsCF_convention_string  C3S-0.1 [Other convention] :..."CF-1.6 C3S-0.1"

Multiple conventions may be included (separated by blank spaces)

title

"<short institution name> seasonal forecast model output prepared for C3S"

CF: Free text

ACDD (highly recommended)

"ECMWF seasonal forecast model output prepared for C3S"
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.
sourceA 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

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.

commentFree 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"
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
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)
level_type

Controlled Vocabulary

"surface", "pressure", "soil"

"pressure"A string indicating the type of the level where the variable comes from
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

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"

Spatial Coordinates

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.

commentFree 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)

historyEmpty 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)		Axisstandard_namelong_name
(CMIP5)		units
(CF canonical units)		positivevalid_min
(CMIP5)		valid_max
(CMIP5)		boundsNotes
doublelatlatYlatitudelatitudedegrees_northN/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]

doublelonlonXlongitudelongitudedegrees_eastN/A0.360.lon_bndsValues (1x1deg grid) prescribed:
center of 1-degree cells
dimension lon=360

[0.5 , 1.5 , ..., 358.5, 359.5]

double
Type
(CMIP5)		Coordinate Name
(CMIP5)		Dimension Names
(CMIP5)		Axisstandard_namelong_name
(CMIP5)		units
(CF canonical units)		positivevalid_min
(CMIP5)		valid_max
(CMIP5)		boundsNotes
doublelatlatYlatitudelatitudedegrees_northN/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]

doublelonlonXlongitudelongitudedegrees_eastN/A0.360.lon_bndsValues (1x1deg grid) prescribed:
center of 1-degree cells
dimension lon=360

[0.5 , 1.5 , ..., 358.5, 359.5]

doubleplevplevZair_pressurepressure

Pa

downN/AN/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)


doubledepthdepthZdepthdepth

m

downN/AN/Adepth_bndsOnly used for soil model levels
NOTE: Number and depth of levels is not prescribed by C3S
doubleheight(scalar auxiliary coordinate)Zheightheightmup 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

 


 realizationstr31=31

E realizationrealization1N/AN/AN/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 done given by the cell boundaries (lat_bnds, lon_bnds)

Time Coordinates

TypeCoordinate NameDimension NamesAxisstandard_namelong_namecalendarunitsboundsNotes
doublereftimeN/AN/Aforecast_reference_time"Start date of the forecast"gregorianUDUNITS time units
e.g.
"hours since YYYY-MM-DD hh:mm:ss TZhh:TZmm"		N/AIn 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)
doubleleadtimeleadtimeN/Aforecast_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

doubletimeleadtimeN/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 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

...

Values (1x1deg grid) prescribed:

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

...

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 NameDimensionsComments
time_bndsleadtime, bnds
leadtime_bnds
lat_bndslat, bndsValues (1x1deg grid) prescribed:
[-90., -89.], [-89., -88.], ... [89., 90.]
lon_bndslon, bnds

Values (1x1deg grid) prescribed:

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

depth_bndsdepth, bndsShould 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		valuecomment
grid_mappinghcrs

Conditional attributes

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

attribute namevaluecomment
_FillValueSet by netCDF libraryThose 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_valueSet 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 namevaluecomment
valid_maxTBD see below
valid_minTBDsee below


Info
titlevalid 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)		dimensionsstandard_namelong_name
(CMIP5)		unitscoordinatesvalid_minvalid_maxglobal attributes
sftlflat,lonland_area_fraction"Land Area Fraction"1

"lat lon"



01

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

oroglat,lonsurface_altitude"Surface Altitude"m"lat lon"

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

Surface Fields (defined at a given height level)



attributes

name
(CMIP5/6&C3S

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 hcrs ;
    hcrs:grid_mapping_name = "latitude_longitude" ;

Variables

Common attributes

The following attributes must be included in all the variables

...

Static Fields

  attributes name
(CMIP5
)dimensionsstandard_namelong_name
(CMIP5/6&C3S)		unitscoordinatescell_methodsvalid_minvalid_maxglobal attributesNOTES
sftlf
tasleadtime,lat,lon
land
air_
area_fraction
temperature"
Land Area Fraction
Near-Surface Air Temperature"
1
K

"reftime realization time leadtime height lat lon"

 



"leadtime: point"

C3S: required 

oroglat,lonsurface_altitude"Surface Altitude"m"lat lon" 

...

CF: recommended



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

height is usually 2m

height:valid_min = 1.;
height:valid_max = 10. ;

 

 

attributes name
(CMIP5/6&C3S)dimensionsstandard_namelong_name
(CMIP5/6&C3S)unitscoordinatescell_methodsNOTEStastime,lat,lonair_temperature"Near-Surface Air Temperature"K

"reftime realization time leadtime height lat lon"

 

 

"time: point"
C3S: required 
CF: recommended

height is usually 2m

tasmaxleadtime,lat,lonair_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

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

"reftime realization time leadtime height lat lon"

"

time

leadtime:

maximum

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)tasmin

hours)

leadtime_bnds, time_bnds are required

tdpsleadtime
time
,lat,lon
air
dew_point_temperature"
Daily Minimum Near-Surface Air
2m Dewpoint Temperature"K"reftime realization time leadtime height lat lon""
time: minimum (interval: <value> <unit>)
leadtime: point"

C3S:
interval is
required
.
 
CF
:
: recommended


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

interval is optional

height is usually 2m

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

tdps

height:valid_min = 1.;
height:valid_max = 10. ;

 
uasleadtime
time
,lat,lon
dew
x_
point_temperature"2m dewpoint temperature"
windEastward Near-Surface Windm s-1
K
"reftime realization time leadtime height lat lon""
time
leadtime: point"

C3S: required 
CF: recommended

height is usually 2m

 

uas



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

height is usually 10m


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

vasleadtime
time
,lat,lon
x
y_wind
Eastward vastime,lat,lony_windNorthward Near-Surface Windm s-1"reftime realization time leadtime height lat lon""time: point"
C3S: required 
CF: recommended

height is usually 10m

wsgmax

 

Northward Near-Surface Windm s-1"reftime realization time leadtime height lat lon""leadtime: point"

C3S: required 
CF: recommended

height is usually 10m




"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

time
leadtime,lat,lonwind_speed_of_gust

"Maximum Wind Speed of Gust"

 


N/A in CMIP

m s-1"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 10m 

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

 

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

...

leadtime_bnds, time_bnds are required


Surface Fields (not defined at a height level)

...



attributes
 


name
(CMIP5/6&C3S)		dimensionsstandard_namelong_name
(CMIP5/6&C3S)		unitscoordinatescell_methods
NOTES
valid_minvalid_maxglobal attributesComments
psl
time
leadtime,lat,lonair_pressure_at_sea_level"Sea Level Pressure"Pa"reftime realization time leadtime lat lon""leadtime: point"

C3S: required 
CF: recommended
 


"frequency":"6hr"
"level_type": "surface"
"modeling_realm":"atmos"
clt
time
leadtime,lat,loncloud_area_fraction"Total Cloud Fraction"1"reftime realization time leadtime lat
lon
lon""leadtime: point"

C3S: required 
CF: recommended


"frequency":"6hr"
"level_type": "surface"
"
time: point"
C3S: required 
CF: recommended
 
modeling_realm":"atmos"
tslleadtime
tsltime
,lat,lonsoil_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
time
leadtime,lat,lonsea_surface_temperature"Sea Surface Temperature"K"reftime realization time leadtime lat lon""leadtime: point"

C3S: required 
CF: recommended

 



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

sitemptop

sitemptop

 


N/A in CMIP

time
leadtime,lat,lonsea_ice_temperature

"Surface

temperature

Temperature of

sea ice

Sea Ice"

N/A in CMIP

K"reftime realization time leadtime lat lon""leadtime: point"

C3S: required 
CF: recommended
 


"frequency":"6hr"
"level_type": "surface"
"modeling_realm":"seaIce"
sic
time
leadtime,lat,lonsea_ice_area_fraction"Sea Ice Area Fraction"1"reftime realization time leadtime lat lon""leadtime: point"

C3S: required 
CF: recommended
 


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

mrlsl


leadtime

 

N/A in CMIP

time
,depth,lat,lon
mass
moisture_content_of
_water
_
in_
soil_layer

"Water Content per Unit Area of Soil Layers"

 

N/A in CMIP


kg m-2"reftime realization time leadtime depth lat lon""leadtime: point"

C3S: required 
CF: recommended
 

lwesnw



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

lwesnw

 


N/A in CMIP

time

rhosn

 

leadtime,lat,lonlwe_thickness_of_surface_snow_amount

"Liquid Water Equivalent Thickness of Surface Snow Amount"

N/A in CMIP

m"reftime realization time leadtime lat lon""leadtime: point"

C3S: required 
CF: recommended


"frequency":"day"
"time: point"
C3S: required 
CF: recommended
 
"level_type": "surface"
"modeling_realm":"land"

rhosn


N/A in CMIP

time
leadtime,lat,lonsnow_density

"Snow

density

Density"

 


N/A in CMIP

kg m-3"reftime realization time leadtime lat lon""leadtime: point"

C3S: required 
CF: recommended
 


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

lweprs

 


N/A in CMIP

time
leadtime,lat,lonlwe_thickness_of_stratiform_precipitation_amount"Liquid Water Equivalent Thickness of Stratiform Precipitation Amount"
 


N/A in CMIP

m"reftime realization time leadtime lat lon""time: sum"
 
 

m"reftime realization time leadtime lat lon""leadtime: sum"

 


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

leadtime_bnds, time_bnds are required

lweprc

lweprc

 


N/A in CMIP

time
leadtime,lat,lonlwe_thickness_of_convective_precipitation_amount"Liquid Water Equivalent Thickness of Convective 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

lwepr

 


N/A in CMIP

time
leadtime,lat,lonlwe_thickness_of_precipitation_amount"Liquid Water Equivalent Thickness of Total 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

 

lweprsn

 


N/A in CMIP

time
leadtime,lat,lonlwe_thickness_of_snowfall_amount"Liquid Water Equivalent Thickness of Snowfall 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

hfss
time
leadtime,lat,lonsurface_upward_sensible_heat_flux"Surface Upward Sensible Heat Flux"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

 

hfls
time
leadtime,lat,lonsurface_upward_latent_heat_flux"Surface Upward Latent Heat Flux"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

 

rsds
time
leadtime,lat,lonsurface_downwelling_shortwave_flux_in_air"Surface Downwelling Shortwave Radiation"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

 

rlds
time
leadtime,lat,lonsurface_downwelling_longwave_flux_in_air"Surface Downwelling Longwave Radiation"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

 

rss
time
leadtime,lat,lonsurface_net_downward_shortwave_flux"Net Shortwave Surface Radiation"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

 

rls
time
leadtime,lat,lonsurface_net_downward_longwave_flux"Net Longwave Surface Radiation"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

rst

rst

 


N/A in CMIP

time
leadtime,lat,lontoa_net_downward_shortwave_flux

"TOA Net

Downward

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

 

rlt

 


N/A in CMIP

time
leadtime,lat,lontoa_net_downward_longwave_flux

"TOA Net

Downward

Longwave Radiation"

N/A in CMIP

W m-2"reftime realization time leadtime lat lon""leadtime: mean (interval: <value> <unit>)"
C3S: interval is r equired.
CF: interval is optional


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

leadtime_bnds, time_bnds are required

 

rsdt
time
leadtime,lat,lontoa_incoming_shortwave_flux"TOA Incident Shortwave Radiation"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

 

tauu
time
leadtime,lat,lonsurface_downward_eastward_stress"Surface Downward Eastward Wind Stress"Pa"reftime realization time leadtime lat lon""leadtime: mean (interval: <value> <unit>)"
C3S: interval is
required.
CF: interval is optional
required.
CF: interval is optional


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

leadtime_bnds, time_bnds are required

tauvleadtime
 tauvtime
,lat,lonsurface_downward_northward_stress"Surface Downward Northward Wind Stress"Pa"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

lwee

 


N/A in CMIP

time

 

leadtime,lat,lonlwe_thickness_of_water_evaporation_amount

"Liquid Water Equivalent Thickness of Evaporation Amount"

N/A in CMIP

m"reftime realization time leadtime lat lon"
"reftime realization time leadtime lat lon""time: sum"
 
 
"leadtime: sum"

 


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

leadtime_bnds, time_bnds are required

mrroa

N/A in CMIP

time
leadtime,lat,lonrunoff_amount
 

"Total Run-off Amount"

N/A in CMIP

kg m-2"reftime realization time leadtime lat lon""leadtime: sum"

 
 


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

leadtime_bnds, time_bnds are required

mrroas

 

N/A in CMIP

time
leadtime,lat,lonsurface_runoff_amount
 

"Surface Run-off Amount"

N/A in CMIP

kg m-2"reftime realization time leadtime lat lon""leadtime: sum"

 

 



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

leadtime_bnds, time_bnds are required

mrroab

 

N/A in CMIP

time
leadtime,lat,lonsubsurface_runoff_amount
 

"Subsurface Run-off Amount"

N/A in CMIP

kg m-
2"reftime realization time leadtime lat lon""time: sum"
 
 

Pressure Level Fields

2"reftime realization time leadtime lat lon""leadtime: sum"

 


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

leadtime_bnds, time_bnds are required

Pressure Level Fields

 

   


attributes
  attributes 
name
(CMIP5)		dimensionsstandard_namelong_name
(CMIP5)		unitscoordinatescell_methodsvalid_minvalid_maxglobal attributesNOTES
zgtimeleadtime,plev,lat,longeopotential_height"Geopotential Height"m"reftime realization time leadtime plev lat lonlon""leadtime: point"

C3S: required 
CF: recommended


"frequency":"12hr"
"level_type": "pressure"
"time: point"
C3S: required 
CF: recommended
 modeling_realm":"atmos"
taleadtimetatime,plev,lat,lonair_temperature"Air Temperature"K"reftime realization time leadtime plev lat lon""leadtime: point"

C3S: required 
CF: recommended
 

"frequency":"12hr"
"level_type": "pressure"
"modeling_realm":"atmos"
hustimeleadtime,plev,lat,lonspecific_humidity"Specific Humidity"1"reftime realization time leadtime plev lat lon""leadtime: point"

C3S: required 
CF: recommended
 : recommended


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

rv

N/A in CMIP

timeleadtime,plev,lat,lonatmosphere_relative_vorticity

"Relative Vorticity"

N/A in CMIP

s-1"reftime realization time leadtime plev lat lon""leadtime: point"

C3S: required 
CF: recommended
 

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

wnddiv

N/A in CMIP

timeleadtime,plev,lat,londivergence_of_wind

"Divergence of Wind"

N/A in CMIP

s-1"reftime realization time leadtime plev lat lonlon""leadtime: point"

C3S: required 
CF: recommended


"frequency":"12hr"
"level_type": "pressure"
"time: point"
C3S: required 
CF: recommended
 modeling_realm":"atmos"
ualeadtimeuatime,plev,lat,lonx_wind"Eastward Wind"m s-1"reftime realization time leadtime plev lat lon""leadtime: point"

C3S: required 
CF: recommended
 

"frequency":"12hr"
"level_type": "pressure"
"modeling_realm":"atmos"
vatimeleadtime,plev,lat,lony_wind"Northward Wind"m s-1"reftime realization time leadtime plev lat lon""leadtime: point"

C3S: required 
CF: recommended
 


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