List of requested variables

Introduction

The tables shown on this page summarize the list of variables requested from the providers of "Operational Products of Seasonal Forecasts", according to the invitation to tender C3S_330 (more info here). Note this list has been also later updated to reflect the evolution of those requirements.

This list includes some basic information for encoding those variables in netCDF. A more detailed information page about the encoding in netCDF will be found in the Guide to NetCDF encoding for C3S seasonal providers, which should be considered the definitive specification for the data encoding of the files to be provided.

Note that alongside the basic encoding information in netCDF, i.e. CF standard name and canonical units, the tables contain some details about GRIB encoding which was used in the previous C3S seasonal forecast datasets.

Requested variables from providers

Static Data

GRIB			netCDF
name	parameter ID	units	CF standard name	canonical units
Land-sea mask	172	(0-1)	land_area_fraction	1
Geopotential	129	m² s^-2	surface_altitude	m

Surface Fields

Sub-daily data

	GRIB			netCDF
time step	name	parameter ID	units	CF standard name	canonical units
6h	2 metre temperature	167	K	air_temperature	K
6h	2 metre dewpoint temperature	168	K	dew_point_temperature	K
6h	10 metre U wind component	165	m s^-1	x_wind	m s^-1
6h	10 metre V wind component	166	m s^-1	y_wind	m s^-1
6h	Mean sea level pressure	151	Pa	air_pressure_at_sea_level	Pa
6h	Total cloud cover	164	(0-1)	cloud_area_fraction	1
6h	Soil temperature level 1	139	K	soil_temperature	K
6h	Sea surface temperature ⁽¹⁾	34	K	sea_surface_temperature	K
6h	Sea ice temperature ⁽¹⁾	500172	K	sea_ice_temperature	K

(1) GRIB data streams could contain those variables as a composite field with parameter ID=139

Daily instantaneous data

	GRIB			netCDF
time step	name	parameter ID	units	CF standard name	canonical units
24h	Sea-ice cover	31	(0-1)	sea_ice_area_fraction	1
24h	Volumetric soil water layer 1 ⁽²⁾	39	m³ m^-3	moisture_content_of_soil_layer ⁽²⁾	kg m^-2
24h	Volumetric soil water layer 2 ⁽²⁾	40	m³ m^-3
24h	Volumetric soil water layer 3 ⁽²⁾	41	m³ m^-3
24h	Volumetric soil water layer 4 ⁽²⁾	42	m³ m^-3
24h	Snow depth	141	m of water equivalent	lwe_thickness_of_surface_snow_amount	m
24h	Snow density	33	kg m^-3	snow_density	kg m^-3
24h	Total column water vapour	137	kg m^-2	atmosphere_mass_content_of_water_vapor	kg m^-2
24h	Total column cloud liquid water	78	kg m^-2	atmosphere_mass_content_of_cloud_liquid_water	kg m^-2
24h	Total column cloud ice water	79	kg m^-2	atmosphere_mass_content_of_cloud_ice	kg m^-2

(2) soil water content should be provided for all native model levels (so 39-42 GRIB parameter IDs just apply to ECMWF/IFS soil model)

Daily time-aggregated data (accumulations, max/min,etc)

	GRIB			netCDF
time step	name	parameter ID	units	CF standard name	canonical units
24h	Maximum temperature at 2 metres in the last 24 hours	51	K	air_temperature	K
24h	Minimum temperature at 2 metres in the last 24 hours	52	K	air_temperature	K
24h	10 metre wind gust since previous post-processing	49	m s^-1	wind_speed_of_gust	m s^-1
24h	Large-scale precipitation ⁽⁴⁾	142	m	lwe_thickness_of_stratiform_precipitation_amount ⁽⁴⁾	m
24h	Convective precipitation ⁽⁴⁾	143	m	lwe_thickness_of_convective_precipitation_amount ⁽⁴⁾	m
24h	Total precipitation	228	m	lwe_thickness_of_precipitation_amount	m
24h	Snowfall	144	m of water equivalent	lwe_thickness_of_snowfall_amount	m
24h	Surface sensible heat flux	146	J m^-2	surface_upward_sensible_heat_flux	W m^-2
24h	Surface latent heat flux	147	J m^-2	surface_upward_latent_heat_flux	W m^-2
24h	Surface solar radiation downwards	169	J m^-2	surface_downwelling_shortwave_flux_in_air	W m^-2
24h	Surface thermal radiation downwards	175	J m^-2	surface_downwelling_longwave_flux_in_air	W m^-2
24h	Surface net solar radiation	176	J m^-2	surface_net_downward_shortwave_flux	W m^-2
24h	Surface net thermal radiation	177	J m^-2	surface_net_downward_longwave_flux	W m^-2
24h	Top net solar radiation	178	J m^-2	toa_net_downward_shortwave_flux	W m^-2
24h	Top incoming solar radiation	212	J m^-2	toa_incoming_shortwave_flux	W m^-2
24h	Top net thermal radiation	179	J m^-2	toa_net_downward_longwave_flux	W m^-2
24h	Eastward turbulent surface stress	180	N m^-2 s	surface_downward_eastward_stress	Pa
24h	Northward turbulent surface stress	181	N m^-2 s	surface_downward_northward_stress	Pa
24h	Evaporation	182	m of water equivalent	lwe_thickness_of_water_evaporation_amount	m
24h	Runoff ⁽⁵⁾	205	m	runoff_amount ⁽⁵⁾	kg m^-2
24h	Surface runoff	8	m	surface_runoff_amount	kg m^-2
24h	Sub-surface runoff	9	m	subsurface_runoff_amount	kg m^-2

(4) Large-scale and convective precipitation are not required if total precipitation is provided (and viceversa)
(5) Runoff is not required if both surface and sub-surface runoff are provided (and viceversa)

NOTES:

Accumulations in GRIB are made from the beginning of the forecast, while in netCDF they are made accordingly to the description contained in the cell bounds/methods
In netCDF, cell bounds and methods are also used to appropriately define maximum/minimum, etc.

Pressure Levels Fields

At the following 12 pressure levels (hPa): 1000, 925, 850, 700, 500, 400, 300, 200, 100, 50, 30 and 10

	GRIB			netCDF
time step	name	parameter ID	units	CF standard name	canonical units
12h	Geopotential	129	m² s^-2	geopotential_height	m
12h	Temperature	130	K	air_temperature	K
12h	Specific humidity	133	kg kg^-1	specific_humidity	1
12h	Vorticity (relative) (*)	138	s^-1	atmosphere_relative_vorticity (*)	s^-1
12h	Divergence (*)	155	s^-1	divergence_of_wind (*)	s^-1
12h	U component of wind	131	m s^-1	x_wind	m s^-1
12h	V component of wind	132	m s^-1	y_wind	m s^-1

(*) Vorticity and divergence are not required if U and V are provided (and viceversa)

Ocean variables

List agreed on 28th October 2019 (Updated on 13th March 2020)

Time frequency	Monthly averages
Grid	1x1-degree (C3S atmosphere grid)
File format	netCDF (see encoding proposal)

name	CF standard name	units	comments
Sea surface salinity	sea_water_practical_salinity	psu
Depth of 20C isotherm	depth_of_isosurface_of_sea_water_potential_temperature	m
Depth of 26C isotherm	depth_of_isosurface_of_sea_water_potential_temperature	m
Depth of 28C isotherm	depth_of_isosurface_of_sea_water_potential_temperature	m
Depth of 14C isotherm	depth_of_isosurface_of_sea_water_potential_temperature	m
Depth of 17C isotherm	depth_of_isosurface_of_sea_water_potential_temperature	m
Mean sea water potential temperature in upper 300 m	sea_water_potential_temperature	K
Mean salinity in upper 300 m	sea_water_practical_salinity	psu
Sea surface height above geoid	sea_surface_height_above_geoid	m
Mixed-layer depth defined by sigma theta 0.01 kg/m3	ocean_mixed_layer_thickness_defined_by_sigma_theta	m	Time-averaging: monthly average of mixed-layer depths calculated from hi-freq T,S (at least 6-hourly values)
Mixed-layer depth defined by sigma theta 0.03 kg/m3	ocean_mixed_layer_thickness_defined_by_sigma_theta	m	Time-averaging: monthly average of mixed-layer depths calculated from hi-freq T,S (24-hourly values are ok)
Sea ice thickness	sea_ice_thickness	m	Mean thickness where there is ice

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