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Note that in the tables below, "an" and "fc" is just a label used for convention to archive the data in MARS.

Table 1: stream=oper/mnth/moda, levtype=sfc: surface parameters: instantaneous

	name	units	Variable name in CDS	shortName	paramId	an	fc	GRIB1	GRIB2	Used as forcing field
1	Lake mix-layer temperature	K	lake_mix_layer_temperature	lmlt	228008	x		x
2	Lake mix-layer depth	m	lake_mix_layer_depth	lmld	228009	x		x
3	Lake bottom temperature	K	lake_bottom_temperature	lblt	228010	x		x
4	Lake total layer temperature	K	lake_total_layer_temperature	ltlt	228011	x		x
5	Lake shape factor	dimensionless	lake_shape_factor	lshf	228012	x		x
6	Lake ice temperature	K	lake_ice_temperature	lict	228013	x		x
7	Lake ice depth	m	lake_ice_depth	licd	228014	x		x
8	Snow cover	%	snow_cover	snowc	260038		x		x
9	Snow depth	m	snow_depth	sde	3066		x		x
10	Snow albedo	(0 - 1)	snow_albedo	asn	32	x		x
11	Snow density	kg m**-3	snow_density	rsn	33	x		x
12	Volumetric soil water layer 1¹	m3 m-3	volumetric_soil_water_layer_1	swvl1	39	x		x
13	Volumetric soil water layer 2¹	m3 m-3	volumetric_soil_water_layer_2	swvl2	40	x		x
14	Volumetric soil water layer 3¹	m3 m-3	volumetric_soil_water_layer_3	swvl3	41	x		x
15	Volumetric soil water layer 4¹	m3 m-3	volumetric_soil_water_layer_4	swvl4	42	x		x
16	Leaf area index, low vegetation²	m2 m-2	leaf_area_index_low_vegetation	lai_lv	66		x	x
17	Leaf area index, high vegetation²	m2 m-2	leaf_area_index_high_vegetation	lai_hv	67		x	x
18	Surface pressure	Pa	surface_pressure	sp	134		x	x		x
19	Soil temperature level 1¹	K	soil_temperature_level_1	stl1	139	x		x
20	Snow depth water equivalent	m of water equivalent	snow_depth_water_equivalent	sd	141	x		x
21	10 metre U wind component	m s**-1	10m_u_component_of_wind	u10	165		x	x		x
22	10 metre V wind component	m s**-1	10m_v_component_of_wind	v10	166		x	x		x
23	2 metre temperature	K	2m_temperature	2t	167		x	x
24	2 metre dewpoint temperature	K	2m_dewpoint_temperature	2d	168		x	x
25	Soil temperature level 2¹	K	soil_temperature_level_2	stl2	170	x		x
26	Soil temperature level 3¹	K	soil_temperature_level_3	stl3	183	x		x
27	Skin reservoir content	m of water equivalent	skin_reservoir_content	src	198	x
28	Skin temperature	K	skin_temperature	skt	235	x		x
29	Soil temperature level 4¹	K	soil_temperature_level_4	stl4	236	x		x
30	Temperature of snow layer	K	temperature_of_snow_layer	tsn	238	x		x
31	Forecast albedo	(0 - 1)	forecast_albedo	fal	243		x	x

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²Leaf Area Index (LAI) parameters are based on a monthly climatology as explained IFS model documentation CY45R1. So the user will only see monthly variability, but not inter-annual variability.

Table 2: stream=oper/mnth/moda, levtype=sfc: surface parameters: accumulations

	name	units	Variable name in CDS	shortName	paramId	fc	GRIB1	GRIB2	Used as forcing field
1	Surface runoff	m	surface_runoff	sro	8	x	x
2	Sub-surface runoff	m	sub_surface_runoff	ssro	9	x	x
3	Snowmelt	m of water equivalent	snowmelt	smlt	45	x	x
4	Snowfall	m of water equivalent	snowfall	sf	144	x	x		x
5	Surface sensible heat flux	J m**-2	surface_sensible_heat_flux	sshf	146	x	x
6	Surface latent heat flux	J m**-2	surface_latent_heat_flux	slhf	147	x	x
7	Surface solar radiation downwards	J m**-2	surface_solar_radiation_downwards	ssrd	169	x	x		x
8	Surface thermal radiation downwards	J m**-2	surface_thermal_radiation_downwards	strd	175	x	x		x
9	Surface net solar radiation	J m**-2	surface_net_solar_radiation	ssr	176	x	x		x
10	Surface net thermal radiation	J m**-2	surface_net_thermal_radiation	str	177	x	x		x
11	Total Evaporation	m of water equivalent	total_evaporation	e	182	x	x
12	Runoff	m	runoff	ro	205	x	x
13	Total precipitation	m	total_precipitation	tp	228	x	x		x
14	Evaporation from the top of canopy	m of water equivalent	evaporation_from_the_top_of_canopy	evatc	228100	x		x
15	Evaporation from bare soil	m of water equivalent	evaporation_from_bare_soil	evabs	228101	x		x
16	Evaporation from open water surfaces excluding oceans	m of water equivalent	evaporation_from_open_water_surfaces_excluding_oceans	evaow	228102	x		x
17	Evaporation from vegetation transpiration	m of water equivalent	evaporation_from_vegetation_transpiration	evavt	228103	x		x
18	Potential evaporation	m	potential_evaporation	pev	228251	x	x

Accumulations are described in section 140385203 ERA5-Land: data documentation#accumulations. The accumulations in monthly means (stream=moda/mnth) are described in section monthly means

How to use lake-related fields

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The ECMWF model also contains an ice module, a snow module and a bottom sediments module. The present setup of the IFS is running with no bottom sediment and snow modules (snow accumulation over ice is not allowed and snow parameters are used only for albedo purposes). In the implementation in the IFS lake ice can be fractional within a grid-box with inland water (10 cm of ice means 100 % of a grid-box or tile is covered with ice; 0 cm of ice means 100 % of the grid-box is covered by water; in between a linear interpolation is applied) (Manrique-Sunen et al., 2013). At present, the water balance equation is not included for lakes and the lake depth and surface area are kept constant in time (IFS Documentation, 2017, chapter 8 and 11 ). Lake parametrization also requires the lake fraction CL, lake depth DL (preferably bathymetry), and lake initial conditions. DL is the most important external parameter that uses the lake parametrization.

Known issues

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title	Uncertainty fields

As it was done for ERA5, the original plan for ERA5-Land was to provide an estimate of the uncertainty fields based on a dedicated 10-member ensemble run. The latter generated an ensemble of forcing fields that should, in principle, reproduce the space of uncertainty for the land surface fields. The first experiments demonstrated that the spread of the ensemble was clearly under dispersive, i.e. the uncertainty was unrealistically low. A reason for this is the low spread shown by the ensemble of ERA5 forcing fields.

As a result of these experiments we took the decision of not providing the uncertainty fields of ERA5-Land. The opposite would have assigned, for instance, unrealistically high confidence to ERA5-land fields in a data assimilation experiment.

Our recommendation is, for the time being, to use the uncertainty estimate of the corresponding ERA5 field, which should provide a second order approximation to the estimate of the real uncertainty. Future experiments will also perturbe, among other, key land surface model parameters, therefore providing a more realistic spread of the ERA5-Land ensemble surface fields.

Three components of the total evapotranspiration have values swapped as follows:
- variable "Evaporation from bare soil" (mars parameter code 228101 (evabs)) has the values corresponding to the "Evaporation from vegetation transpiration" (mars parameter 228103 (evavt)),
- variable "Evaporation from open water surfaces excluding oceans (mars parameter code 228102 (evaow)) has the values corresponding to the "Evaporation from bare soil" (mars parameter code 228101 (evabs)),
- variable "Evaporation from vegetation transpiration" (mars parameter code 228103 (evavt)) has the values corresponding to the "Evaporation from open water surfaces excluding oceans" (mars parameter code 228102 (evaow)).

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title	Low values of snow cover and snow depth on the eastern side of the Antarctic ice sheet

Low values of snow cover and snow depth were found on the eastern side of the Antarctic ice sheet, as shown in Fig. 1. The issue is due to the application of an old glacier mask to the Antarctica, which excludes the patch shown in the figure as glacier. Inaccuracies in the glacier mask are due to errors in satellite measurements datasets. While, due to the lower horizontal resolution, in ERA5 this ice sheet part is a sea point, in ERA5-Land the area is categorised as land without an initial ice mass. Since the initialization doesn't consider a glacier there (estimated at a constant 10 m of snow water equivalent), the low amount of precipitation along with potential excess of sublimation makes them to obtain unrealistic low numbers there.

Fig 1: ERA-Land Snow depth (m of water equivalent) on 01-01-2015 eastern side of the Antarctic ice sheet.

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How to use lake-related fields

Known issues