Introduction of ensemble forecast overlap fields in dissemination

Implementation date: 21 November 2012

ECMWF introduce an extra set of product fields in order to address an issue that occurs at day 10 in accumulated fields of the ensemble forecast (ENS). The additional products are available through dissemination under the name Ensemble Forecast Overlap (EFOV).

The issue was caused by the change in ENS horizontal resolution from higher resolution in leg 1 (0 to 240 hours) to lower resolution in leg 2 (246 to 360 hours). The change in resolution creates incorrect values for accumulations that run across day 10, i.e. those that span forecast time steps 240-246 hours.

The full list of ensemble forecast overlap fields available

name shortName unit paramId
Surface runoff (variable resolution) srovar m 230008
Sub-surface runoff (variable resolution) ssrovar m 230009
Total sky direct solar radiation at surface (variable resolution) fdirvar J m**-2 230021
Clear-sky direct solar radiation at surface (variable resolution) cdirvar J m**-2 230022
Stratiform precipitation (Large-scale precipitation) (variable resolution) lspvar m 230142
Convective precipitation (variable resolution) cpvar m 230143
Snowfall (convective + stratiform) (variable resolution) sfvar m of water equivalent 230144
Boundary layer dissipation (variable resolution) bldvar J m**-2 230145
Surface sensible heat flux (variable resolution) sshfvar J m**-2 230146
Surface latent heat flux (variable resolution) slhfvar J m**-2 230147
Surface solar radiation downwards (variable resolution) ssrdvar J m**-2 230169
Surface thermal radiation downwards (variable resolution) strdvar J m**-2 230175
Surface net solar radiation (variable resolution) ssrvar J m**-2 230176
Surface net thermal radiation (variable resolution) strvar J m**-2 230177
Top net solar radiation (variable resolution) tsrvar J m**-2 230178
Top net thermal radiation (variable resolution) ttrvar J m**-2 230179
East-West surface stress (variable resolution) ewssvar N m**-2 s 230180
North-South surface stress (variable resolution) nsssvar N m**-2 s 230181
Evaporation (variable resolution) evar kg m**-2 230182
Sunshine duration (variable resolution) sundvar s 230189
Longitudinal component of gravity wave stress (variable resolution) lgwsvar N m**-2 s 230195
Meridional component of gravity wave stress (variable resolution) mgwsvar N m**-2 s 230196
Gravity wave dissipation (variable resolution) gwdvar J m**-2 230197
Skin reservoir content (variable resolution) srcvar kg m**-2 230198
Runoff (variable resolution) rovar m 230205
Total precipitation (variable resolution) tpvar m 230228

Further reading

  • A comprehensive description of the Ensemble system and its variable resolution (leg 1 and leg 2) can be found in Newsletter 108 (pp 14-20).

Changes in GRIB API

Support for two following parameters was added to GRIB API.

  • fdirvar = Total sky direct solar radiation at surface (variable resolution)
  • cdirvar = Clear-sky direct solar radiation at surface (variable resolution)