Revisions during 1998

1 April 1998 The model spectral resolution was increased from T213 to T_L319 (improved orography, reduced diffusion, but Gaussian grid unchanged). The other modifications introduced on this occasion (Cyl8r5) were:

1. A new 2-time level semi-Lagrangian numerical scheme: this made possible the use of a Linear Gaussian Grid reflected by the T_L 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:

1st article pdf(500 KB)

2nd article pdf(348 KB)

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

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