Model	CESM 1.2 - CAM 5.3 (Atmosphere) CESM 1.2 - CLM 4.5 (Land surface)
Horizontal resolution and grid	1/2° lat-lon approx
Atmosphere vertical resolution	46 levels in the vertical
Top of atmosphere	0.2 hPa (60 km approx.)
Soil levels (layers)	15 (10 soil layers plus 5 bedrock layers) Layer 1 (soil): 0.0000-0.0279m 0175m Layer 2 (soil): 0.02790175-0.0623m 0451m Layer 3 (soil): 0.06230451-0.1189m 0906m Layer 4 (soil): 0.11890906-0.2122m 1655m Layer 5 (soil): 0.21221655-0.3661m 2891m Layer 6 (soil): 0.36612891-0.6198m 4929m Layer 7 (soil): 0.6198-1.0380m 4929-0,8289m Layer 8 (soil): 10.03808289-1.7276m 3828m Layer 9 (soil): 1.72763828-2.8646m 2961m Layer 10 (soil): 2.86462961-4.7392m Layer 11 (bedrock): 4.7392-7.8298m Layer 12 (bedrock): 7.8298-12.9253m Layer 13 (bedrock): 12.9253-21.3265m Layer 14 (bedrock): 21.3265-35.1776m Layer 15 (bedrock): 35.1776-50.0000m 3.8019m
Time step	Main (Physics) Time-step: 30 minutes. “Tracer” Advection Time step: 225 seconds (1/8 of the Physics time step) Fluid-Dynamics Time step: 56.25 seconds (1/32 of the Physics time step).

3. Initialization and initial condition (IC) perturbations

3.1 Atmosphere and land

	Hindcast	Forecast
Atmosphere initialization	ERA5	ECMWF IFS operational analysis
Atmosphere IC perturbations	10	10
Land Initialization	Forced

(obs. atmosphere)

monthly run

initialized from 10-year spin-up

Forced (obs. atmosphere) monthly run

initialized from 10-year spin-up

from a continuous transient simulation with initial-date January 1993, started after a 10 year spinup (with climatological forcings)	Forced monthly run from a continuous transient simulation with initial-date January 1993, started after a 10 year spinup (with climatological forcings)
Land IC perturbations	3	3
Soil moisture initialization	From land initialization	From land initialization
Snow initialization	From land initialization	From land initialization
Unperturbed control forecast?	NO	NO
Horizontal resolution of perturbation	N/A	N/A
Perturbations in +/- pairs	NO	NO
Data assimilation method for control analysis	ERA5	ECMWF operational

Detailed documentation:

For more details on atmospheric DA, see ECMWF operational analysis documentation at: https://www.ecmwf.int/en/elibrary/16666-part-ii-data-assimilation

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Model dynamics perturbations	NO
Model physics perturbations	YES (Ocean Model only, only during perturbed data assimilation cycles)
If there is a control forecast, is it perturbed?	There is no control forecast

Detailed documentation: For more info on ocean DA perturbations, see Brankart (2013) DOI: https://doi.org/10.1016/j.ocemod.2013.02.004

CMCC technical documentation Gualdi et al (2020) CMCC Technical Note RP0288 DOI: https://doi.org/10.25424/CMCC/SPS3.5

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