9 March 2004 Introduction of Cycle 28r1. This version includes the following mainly minor, technical modifications :
- Data assimilation changes:
- new snow analysis using NESDIS snow cover product;
- Improved use of Goes BUFR winds;
- Improved clouds in 4D-Var minimisation;
- Re-introduction of ERS-2 scatterometer winds (with adjusted
pre-screening and limited coverage) . - Variational QC corrected for 3D-Var (with impact of the BC
project and ERA-40 reruns only);
- Numerics changes:
- Semi Lagrangian fix for polar vortex instabilities;
- Several code modifications to prepare the L91 version.
- Physics changes:
- Convection clean-up;
- Optimisation of linearised physics and more optimisations
of physics code;
- Oceanic Waves:
- Introduction of subgrid scale (unresolved) bathymetry effects;
- A fix to the EPS wave-model interface (Charnock variable)
- The overall impact is very small in terms of forecast performance.
- The parametrisation of the unresolved bathymetry has resulted in an improved performance of the ocean wave system, while in the free atmosphere a slight negative impact can be detected over the southern hemisphere towards the later stages of the medium-range.
- The change to the new cycle is transparent for users apart from a change in the atmospheric model identification number in GRIB headers, which will be set to 122.
- The wave model identification numbers will also change and will be:
- 114 for the Global Wave Model and
- 214 for the European Waters Wave Model.
29 June 2004 ECMWF implemented the Early Delivery Forecasting System which comprises two main 6-hour 4D-Var analysis and forecast cycles for 00 and 12 UTC (DA stream) with two additional 12-hour 4D-Var analysis (DCDA stream) and first guess forecast cycles. These additional cycles are run with a delayed cut-off time of 14 hours (with respect to the nominal analysis times). The analysis observation windows are 21-09 UTC for the 00 UTC analysis and 09-21 UTC for the 12 UTC analysis. The first guess forecasts are used to initialise the main operational 00 and 12 UTC assimilation and forecast cycles. Trials have shown that the quality of the two first guesses is sufficiently high to allow an early running of the 6-hour 4D-Var assimilations at around 0400 and 1600 UTC without any loss in quality in the ensuing forecasts compared with the previous operational system.
- ECMWF products are now provided some three to four hours earlier in line with the timing of the Early Delivery Forecasting System.
- The change to the new cycle is transparent for users apart from a change in the atmospheric model identification number in GRIB headers, which will be set to 123.
- The wave model identification numbers will also change and will be:
- 115 for the Global Wave Model and
- 215 for the European Waters Wave Model.