Cycle 26r1 summary of changes

29 April 2003 Introduction of Cycle 26r1. This is a technical change only and involves the writing of observations directly into the Observation Data Base (ODB).

The new model cycle is used throughout the Centre's forecast suites, the T511 main run, the EPS and the BC Optional Project. The atmospheric model identification number in the GRIB headers changed from 202 to 203.

7 October 2003 Introduction of Cycle 26r3. Changes from the previous operational version (Cycle 26r1) include:

  1. a new formulation of the humidity analysis (modified background-error covariances, corrected calculation of background-errors for SSMI that uses FASTEM emissivity model over sea);
  2. new data streams (AIRS from Aqua, AMSU-B, AMSU-A from Aqua, Japanese wind profilers, Meteosat5, GOES9 and GOES12 WV clear sky radiances, GOES12 winds and MIPAS ozone-profile retrievals);
  3. monitoring of ENVISAT data: SCIAMACHY, GOMOS, and MIPAS;
  4. a new linear radiation scheme in 4D-var, a new radiation sampling (HALO) and a new aerosol climatology in the full model;
  5. a relaxation of the convective mass flux limiter for long time steps (used for the EPS and monthly forecasts);
  6. new model parameters (UVB, CAPE, photo-synthetically active radiation, freak waves). Details of the new parameters are:
    • Atmospheric model (Local GRIB table: 128):

      • 57 UVB Downward UV radiation at the surface w m**-2
      • 58 PAR Photosynthetically active radiation at the surface wm**-2
      • 59 CAPE Convective available potential energy J kg**-1
    • Wave model: (Local GRIB table 140):
      • 252 WSK Wave surface kurtosis -
      • 253 BFI Benjamin-Feir index -
      • 254 WSP Wave spectral peakedness s**-1

    For further information please refer to ECMWF Technical Memorandum 366. The fields for these new model parameters are written into MARS and are available through dissemination from all suites and for all default post-processing time steps.

  • The change to the new cycle was transparent for users apart from a change in Model identification number for the atmospheric model in GRIB headers, which was set to 121.
  • Note: after reaching the end of the defined range of possible identifications numbers in cycle 26r1 with 203 it was agreed that the numbers will be recycled.
  • The wave model identification numbers were not changed and continue to be 113 for the Global Wave Model and 213 for the Mediterranean Wave Model.
  • Verification results gathered to date from the experimental suite and from several months of research experiments indicated that, in general, a significant and consistent improvement in the upper air (including humidity) forecasts can be expected from this new cy26r3.



Cycle changes

Please note

Prior to 2006 information on cycle upgrades has been migrated from the old website to the new website "as is". The information has not been reviewed during the migration.