1998 summary of changes

1 April 1998 The model spectral resolution was increased from T213 to TL319 (improved orography, reduced diffusion, but Gaussian grid unchanged). The other modifications introduced on this occasion (Cy18r5) were:

1. A new 2-time level semi-Lagrangian numerical scheme: this made possible the use of a Linear Gaussian Grid reflected by the TL notation already introduced for the EPS configuration in Dec. 1996;

2. Use of a new 2'30" orography reference dataset; as a result, some large errors over Antartica have been corrected and spurious noise in other areas suppressed;

3. Improved sea-ice limits determination.

25 February 1998 Cy18r4

29 June 1998 An hourly, two way coupling of the atmospheric and ocean-wave model was introduced. Predicted ocean waves now provide information to the atmospheric boundary layer.

Other modifications introduced at the same time (Cy18r6) were:

1. the use of both significant and standard wind level winds, temperatures and humidities from radiosondes (geopotential is no longer used);

2. the use of extra off-time data, mostly SYNOPs and DRIBUs;

3. the use of 1D-Var SSM/I total column water vapour;

4. extension of the use of GOES high-resolution winds to the northern extratropics;

5. the use of more TOVS channels over land;

6. the observation operator for 10m winds is now unified for scatterometer, DRIBU and SYNOP observations.

Two articles from the ECMWF Newsletter describing the changes are available:

12 August 1998 METEOSAT5/INDOEX SATOB products have been introduced in the data assimilation.

21 October 1998  Cycles 19r1 A formulation of uncertainties associated to physical processes (stochastic physics) was introduced in the ECMWF Ensemble Prediction System.


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.