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Initialised seasonal forecast of the 20th Century

Update Frequency: Not Planned
Latest Data Update: 2022-05-17
Status: Completed
Online Status: ONLINE
Publication State: Published
Publication Date: 2020-05-04
Download Stats: last 12 months
Dataset Size: 591.54K Files | 190GB


This dataset contains initialised seasonal hindcast experiments for the 20th century, produced using a version of the ECMWF's Intergrated Forecasting System (IFS), and initialised from ECMWF reanalysis (ERA-20C/CERA-20C). Two types of hindcast experiment are included in this dataset:

CSF-20C (Coupled Seasonal Forecasts): This is a hindcast performed with the model fully coupled to the Nucleus for European Modelling of the Ocean (NEMO) ocean model, initialised from CERA-20C reanalysis data.

ASF-20C (Atmospheric Seasonal Forecasts): This is a hindcast performed with prescribed Sea Surface Temperature (SST) and sea-ice boundary conditions at the surface, initialised form ERA-20C reanalysis data.

Hindcasts were started every year between 1901-2009 (inclusive) on the 1st February, 1st May, 1st August and 1st November and are run out for four months from the start date. For each start date, there are either 51 or 25 ensemble members (depending on the season/hindcast).

Monthly mean values for the following variables have been archived here on CEDA (in alphabetical order):

LHF (latent heat-flux)
OLR (outgoing long-wave radiation)
PREC (precipitation)
SHF (sensible heat-flux)
SIC (sea-ice concentration)
SLP (sea-level pressure)
SST (sea surface temperature)
T2 (2m temperature)
U250 (zonal wind at 250 hPa level)
U850 (zonal wind at 850 hPa level)
Us (10m zonal wind speed)
V250 (meridional wind at 250 hPa level)
V850 (meridional wind at 850 hPa level)
Vs (10m meridional wind speed)
Z500 (geopotential at 500 hPa level)

Files for each ensemble member are archived separately and the filetree is in the following format:



[EXPname] =CSF-20C or ASF-20C
[VARname] = Z500, Vs, V850, ... etc.
[INITmonth] = Feb, May, Aug or Nov
[YEAR] =1901, 1902, 1903, ... etc.
[ENSnum] =0, 1, 2, 3, ... etc.

More details of these hindcasts and some previous analysis of these datasets have appeared in the following papers:

Weisheimer, A., Schaller, N., O'Reilly, C., MacLeod, D. A., & Palmer, T. (2017). Atmospheric seasonal forecasts of the twentieth century: multi‐decadal variability in predictive skill of the winter North Atlantic Oscillation (NAO) and their potential value for extreme event attribution. Quarterly Journal of the Royal Meteorological Society, 143(703), 917-926.

O'Reilly, C. H., Heatley, J., MacLeod, D., Weisheimer, A., Palmer, T. N., Schaller, N., & Woollings, T. (2017). Variability in seasonal forecast skill of Northern Hemisphere winters over the twentieth century. Geophysical Research Letters, 44(11), 5729-5738.

MacLeod, D., O'Reilly, C., Palmer, T., & Weisheimer, A. (2018). Flow dependent ensemble spread in seasonal forecasts of the boreal winter extratropics. Atmospheric Science Letters, 19(5), e815.

Parker, T., Woollings, T., Weisheimer, A., O'Reilly, C., Baker, L., & Shaffrey, L. (2019). Seasonal predictability of the winter North Atlantic Oscillation from a jet stream perspective. Geophysical Research Letters, 46(16), 10159-10167.

Weisheimer, A., Decremer, D., MacLeod, D., O'Reilly, C., Stockdale, T. N., Johnson, S., & Palmer, T. N. (2019). How confident are predictability estimates of the winter North Atlantic Oscillation?. Quarterly Journal of the Royal Meteorological Society, 145, 140-159.

Weisheimer, A., Befort, D. J., MacLeod, D., Palmer, T., O’Reilly, C., & Strømmen, K. (2020). Seasonal forecasts of the 20th Century. Bulletin of the American Meteorological Society, (2020).

Citable as:  Weisheimer, A.; O'Reilly, C. (2020): Initialised seasonal forecast of the 20th Century. Centre for Environmental Data Analysis, date of citation.
Abbreviation: Not defined
Keywords: Seasonal, Forecast, model, atmospheric


Previous Info:
No news update for this record
Previously used record identifiers:
No related previous identifiers.
Access rules:
Access to these data is available to any registered CEDA user. Please Login or Register for an account to gain access.
Use of these data is covered by the following licence: When using these data you must cite them correctly using the citation given on the CEDA Data Catalogue record.
Data lineage:

Data downloaded from the ECMWF MARS archive at the resolution provided here and converted to netcdf (from grin). The data were then delivered to the Centre for Environmental Data Analysis for archiving.

Data Quality:
The data has no flaws/corruptions to the best of our knowledge.
File Format:
Data are netCDF formatted.

Related Documents

No documents related to this record were found.

Process overview

This dataset was generated by the computation detailed below.

ECMWF IFS cycle 41r1


The experiments were all performed using the ECMWF's IFS cycle 41r1, with a spectral resolution of T255 and 90 vertical levels. The coupled experiments also include an ocean component that is 1 degree horizontal resultion and 42 vertical levels.

Input Description


Output Description


Software Reference


  • units: m s**-1
  • long_name: 10 metre U wind component
  • var_id: 10U_GDS0_SFC
  • units: m s**-1
  • long_name: 10 metre V wind component
  • var_id: 10V_GDS0_SFC
  • units: K
  • long_name: 2 metre temperature
  • var_id: 2T_GDS0_SFC
  • units: hours
  • long_name: Forecast offset from initial time
  • var_id: forecast_time0
  • units: m**2 s**-2
  • long_name: Geopotential
  • var_id: Z_GDS0_ISBL
  • units: Pa
  • long_name: Mean sea level pressure
  • var_id: MSL_GDS0_SFC
  • units: K
  • long_name: Sea surface temperature
  • var_id: SSTK_GDS0_SFC
  • units: (0 - 1)
  • long_name: Sea-ice cover
  • var_id: CI_GDS0_SFC
  • long_name: Surface latent heat flux
  • units: W m**-2
  • var_id: VAR_147_GDS0_SFC
  • units: W m**-2
  • long_name: Surface sensible heat flux
  • var_id: VAR_146_GDS0_SFC
  • units: W m**-2
  • long_name: Top thermal radiation
  • var_id: VAR_179_GDS0_SFC
  • units: m s**-1
  • long_name: Total precipitation
  • var_id: VAR_228_GDS0_SFC
  • units: m s**-1
  • long_name: U velocity
  • var_id: U_GDS0_ISBL
  • units: m s**-1
  • long_name: V velocity
  • var_id: V_GDS0_ISBL
  • units: degrees_north
  • long_name: latitude
  • var_id: g0_lat_1
  • units: degrees_east
  • long_name: longitude
  • var_id: g0_lon_2

Co-ordinate Variables

Temporal Range
Start time:
End time:
Geographic Extent