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The sub-seasonal range ensemble is run daily based on 00UTC data.  The products cover the period up to Day46 and are derived from a 100 member ensemble with a control and has a resolution of 36km.   The sub-seasonal range ENS is independent of the medium range ENS and has it's own control and sub-seasonal range model climate (ERSUBS-M-climateClimate).

The sub-seasonal range ENS covers a time scale lying between:

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Re-forecasts provide an sub-seasonal range climate (ERSUBS-M-climateClimate) and  and associated probability distribution functions (pdfs) for several variables.  The latest sub-seasonal range ensemble forecasts and the associated probability density functions can be compared with the ERSUBS-M-Climate.  The differences between the two are used as the basis of model products any model drift is effectively removed. 

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The sub-seasonal range model climate (ERSUBS-M-climateClimate) drifts  drifts towards becoming rather too cold at longer lead-times in wintertime high latitudes.  Hence the anomaly in forecast temperatures against ERSUBS-M-climate temperatures may be too large.  The magnitude of the drift is not uniform.  At longer lead-times the trend in northern China is towards colder values but less so in Siberia and Canada.  The variation may be due to the analysed initial snowpack conditions and/or snowmelt in marginal snow cover areas in these areas.  Issues regarding this are being addressed. A multi-layer snow scheme is incorporated.  

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After about 10 days of forecasts, the spread of the ensemble can become very large.  A significant shift can be detected by comparing probability distribution functions of the latest model and the ERSUBS-M-climate.

The re-forecasts are created twice a week (Mondays and Thursdays) and are ready a week before the real-time forecasting suite starts.  Real-time forecasts are calibrated using all the re-forecasts available in a one week window centred on the forecast start day and month. 

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