List of requested variables

Introduction

Starting from the list of parameters requested in the ITT (see here), a review process on them was carried on, and some modifications were proposed to the different providers to C3S seasonal activity (ECMWF, Met Office, MeteoFrance, DWD and CMCC). Additionally, the original list of parameters was to a certain extent incomplete as it just used GRIB parameter codes to describe the variables, in a context where most of the contributors are currently using (or will do in the near future) netCDF format for their provision to C3S.

Taking all of that into account, a revisited list of parameters to be used by the seasonal forecasting providers has been summarized in the tables below, including some basic information for encoding both in GRIB and netCDF. A more detailed information about the encoding in netCDF will be found in the Guide to NetCDF encoding for C3S seasonal providers.

Already existing data streams from the providers

Due to the current characteristics of the C3S service, in its transition from the Proof-of-Concept phase to the Pre-operational phase, this list needs to be understood as a reference of what should be mandatory in the future provisions of data to C3S. In this sense, comparing the data streams' contents from the providers and what is included in the list of requested variables, some slight differences are tolerated, even they are not desirable.

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) For GRIB data streams, those variables can be included 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	mass_content_of_water_in_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

(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 ⁽³⁾	142	m	lwe_thickness_of_stratiform_precipitation_amount ⁽³⁾	m
24h	Convective precipitation ⁽³⁾	143	m	lwe_thickness_of_convective_precipitation_amount ⁽³⁾	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	integral_of_surface_downward_sensible_heat_flux_wrt_time	W s m^-2
24h	Surface latent heat flux	147	J m^-2	integral_of_surface_downward_latent_heat_flux_wrt_time	W s m^-2
24h	Surface solar radiation downwards	169	J m^-2	integral_of_surface_downwelling_shortwave_flux_in_air_wrt_time	W s m^-2
24h	Surface thermal radiation downwards	175	J m^-2	integral_of_surface_downwelling_longwave_flux_in_air_wrt_time	W s m^-2
24h	Surface net solar radiation	176	J m^-2	integral_of_surface_net_downward_shortwave_flux_wrt_time	W s m^-2
24h	Surface net thermal radiation	177	J m^-2	integral_of_surface_net_downward_longwave_flux_wrt_time	W s m^-2
24h	Top net solar radiation	178	J m^-2	integral_of_toa_net_downward_shortwave_flux_wrt_time	W s m^-2
24h	Top incoming solar radiation	174089	J m^-2	integral_of_toa_incoming_shortwave_flux_wrt_time (!)	W s m^-2
24h	Top net thermal radiation	179	J m^-2	integral_of_toa_net_downward_longwave_flux_wrt_time ^(!)	W s m^-2
24h	Eastward turbulent surface stress	180	N m^-2 s	integral_of_surface_downward_eastward_stress_wrt_time	Pa s
24h	Northward turbulent surface stress	181	N m^-2 s	integral_of_surface_downward_northward_stress_wrt_time	Pa s
24h	Evaporation	182	m of water equivalent	lwe_thickness_of_water_evaporation_amount	m
24h	Runoff ⁽⁴⁾	205	m	runoff_amount ⁽⁴⁾	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

(3) Large-scale and convective precipitation are not required if total precipitation is provided (and viceversa)
(4) Runoff is not required if both surface and sub-surface runoff are provided (and viceversa)
(!) Those names are not included within the list of CF standard_names, but they have been derived from existing standard names (toa_incoming_shortwave_flux, toa_net_downward_longwave_flux) following the Guidelines for Construction of CF Standard Names

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 11 pressure levels (hPa): 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)

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