An updated version of the ECMWF forecast and analysis system, cycle 38r1, was implemented on 19 June. The new cycle includes a collection of improvements to the forecast model and the data assimilation system, affecting the high-resolution forecasts and analyses, the ensemble of data assimilations (EDA) and the ensemble prediction system (EPS) including its monthly extension.
Upper-air scores changes are positive and statistically significant when verified against the respective analyses throughout the free atmosphere. Differences are generally smaller and less statistically significant when verified against observations. There are consistent improvements in precipitation forecasts, both in the tropics and extratropics. For 2-metre temperature (T2m) there is a shift to slightly colder values by about 0.1 to 0.2 K. The T2m errors are reduced in the tropics and extra-tropics. There are statistically significant improvements also in the probabilistic skill of the ensemble, consistent with the improvements to the high-resolution forecast.
Cycle 38r1 includes a major improvement of the characterization of the background errors that are used in the 4D-Var analysis. These were obtained from re-computing their climatological structure by gathering statistics from the latest available version of the Ensemble of Data Assimilations (EDA) and model cycle 37r3. The spatial structure and amplitude of the background errors are particularly important because they, to a large extend, determine the impact of the observations in the analysis.
The impact of cycle 38r1 on Northern hemisphere scores is shown in the figure in terms of relative improvement over the previous cycle, verified against both analyses and observations (see legend for details, with the symbols showing the scores at 24 hour, 48 hour, 72 hour etc, up to day 10).
The new cycle introduces new forecast parameters including indices for convective activity, and an extension of the Extreme Forecast Index (EFI) products to include additional parameters and forecast steps.
More details about these changes can be found on the cycle 38r1 web page:
http://www.ecmwf.int/products/changes/ifs_cycle_38r1/