21 November 2000 The model resolution was upgraded from TL319 to TL511 resolution in the deterministic mode, and from TL159 to TL255 in the ensemble mode (EPS). This is roughly a reduction in grid size from 60 to 40km (deterministic) and from 120 to 80km (EPS). Vertical resolution remains unchanged in all model configurations. Other changes included in this model version are:
- the data assimilation now runs its minimization (inner loop) at TL159 (was T63 previously) using new semi-Lagrangian tangent linear and adjoin codes.
- the wave model in the TL511 deterministic model continues to run at approximately 55 km horizontal resolution with an increase in spectral information from 12 to 24 directions and from 25 to 30 frequencies. The wave model in the EPS will run in shallow-water mode with an increased horizontal resolution of approximately 110 km with 12 directions and 25 frequencies (no change). The European-waters model continues to run at approximately 28 km with an increase in spectral information from 25 to 30 frequencies, while the number of direction remains at 24.
ECMWF has issued the following warning:
During the operation of cy21r4 of the ECMWF model from 12 October 1999 to 10 April 2000 the humidity fields in the lower stratosphere both in the analysis and forecast were seriously affected by erroneous moisture. These fields should not be used for research and it is recommended that the model results from the operational archive are not used to provide initial conditions for numerical experiments during this period.
The error is up to 1 to 2 orders of magnitude in a shallow layer just above the tropopause.
This may have a slight affect on the temperature in some regions.