Detailed documentation:

3.

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Initialization and initial condition (IC) perturbations

	Re-forecast	Forecast
Atmosphere initialization	ERA-Interim	ECMWF Operations
Atmosphere IC perturbations	Ensemble data assimilation and leading singular vectors applied to upper air variables	Ensemble data assimilation and leading singular vectors applied to upper air variables
Land Initialization	ERA-Interim land (43r1)	ECMWF Operations
Land IC perturbations	Ensemble data assimilation and leading singular vectors applied to some land fields	Ensemble data assimilation and leading singular vectors applied to some land fields
Soil moisture initialization	ERA-Interim	ECMWF operations
Snow initialization	ERA-Interim	ECMWF operations
Unperturbed control forecast?	Yes	Yes

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Perturbations to sea surface temperature? Yes (5-member ensemble of ocean analyses/re-analyses)

	Re-forecast	Forecast
Ocean initialization	ORAS5	ORTA5
Ocean IC perturbations	Yes - generated through perturbations to assimilated observations and surface forcing	Yes - generated through perturbations to assimilated observations and surface forcing
Unperturbed control forecast?	No	No

Model dynamics perturbations	No
Model physics perturbations	3-lev SPPT and SPBS
If there is a control forecast, is it perturbed?

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Forecast frequency	monthly (LR) quarterly (AR)
Forecast ensemble size	51 (LR) 15 (AR)
Re-forecast years	36 (1981-2016)
Re-forecast ensemble size	25 (LR) 15 (AR)
Calibration (bias correction) period	1993-2016

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