Page History

Creation of SUBS-M-Climate

The SUBS-M-Climate is derived from a set of sub-seasonal range re-forecasts created using the same calendar start dates over several years for data times either side of the time of the sub-seasonal ensemble run itself.  The re-forecast runs are at the same resolution as the sub-seasonal medium range run (currently 36km) and run over the 46-day sub-seasonal range ensemble period. 

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• sub-seasonal range forecast verification metrics are based on the re-forecasts.
  
• re-forecasts allow computation of the SUBS-M-climate which allows actual forecasts to be converted into an anomaly format.   Forecasts in terms of anomalies relative to a model climate (rather than relative to the observed climatology) mean that some calibration for model bias and drift into the products is incorporated.

Selection of sub-seasonal range re-forecasts

Re-forecasts are made every two days during each month on 1/3/5/7/9/11/13/15/17/19/21/23/25/27/29/31 (excluding 29 February).  These are the re-forecast base-dates for sub-seasonal range.

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Running on fixed days of the month allows direct comparison between re-forecasts produced at different resolutions and/or in different years.

Different priorities for M-Climate and SUBS-M-Climate

ECMWF uses different reference periods but essentially the same re-forecast runs to build the M-Climate and the SUBS-M-Climate.   The key difference is that those runs are grouped and used in different ways:  

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