CERA-20C: An Earth system approach to climate reanalysis

Patrick Laloyaux ; Boisséson, Eric de ; Dahlgren, Per

Année de publication
2017
Résumé
ECMWF has completed the production of a new global 20th-century reanalysis which aims to reconstruct the past weather and climate of the Earth system including the atmosphere, ocean, land, waves and sea ice. This coupled climate reanalysis, called CERA-20C, is part of the EU-funded ERA-CLIM2 project, which builds on the ERA-CLIM project. The latter produced ERA-20C, a 20th-century reanalysis for the atmosphere, land and waves only (Poli et al., 2016). First results show that CERA-20C improves on the representation of atmosphere-ocean heat fluxes and of mean sea level pressure compared to previous reanalyses. At the same time, there are undesirable discontinuities in ocean heat content and an excessive accumulation of Arctic sea ice. To account for errors in the observational record as well as model error, CERA-20C provides a ten-member ensemble of climate reconstructions. As expected, the spread of the ensemble decreases over time as the observational record improves. However, verification for the year 2005 suggests that the spread should be larger to give a better indication of the confidence we can have in the reanalysis data.

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