In order to speed up production, ERA5 is being produced by several parallel experiments, each covering a different period, which are then appended together to create the final product. The disadvantage of this approach, is that there can be discontinuities in the final product at the transition points between the different experiments. Here, we document the transition at the end of 2009 and the beginning of 2010. Each experiment begins with a warm up of a few months, which does not become part of the final product, but does overlap with the experiment for the preceding period. This overlap facilitates a comparison of the two experiments to see how well they have converged to a common solution.
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| Fig. 1 Zonal mean temperature (C) of the final ERA5 HRES product (contours) and zonal mean temperature difference (C) for the final ERA5 HRES product minus the warm up (colours), for October to December 2009. The vertical coordinate is pressure of the model levels. | Fig. 2 Zonal mean temperature (C) of the final ERA-Interim product (contours) and zonal mean temperature difference (C) for the final ERA-Interim product minus the warm up (colours), for October to December 2009. The vertical coordinate is pressure of the model levels. | Fig. 3 Zonal mean temperature (C) of the ERA5 EDA control (contours) and zonal mean ERA5 EDA ensemble spread of temperature (C) (colours), for September to November 2009. The vertical coordinate is pressure of the model levels. |
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