The ECMWF system in 1987

The ECMWF data assimilation system in 1987 consisted of a multivariate optimal interpolation analysis, a non-linear normal model initialisation and a high resolution spectral model which produced a first-guess forecast for the subsequent analysis. Data were assimilated every 6 hours.

The forecast model in 1987 used a spectral formulation in the horizontal, with triangular truncation at total wavenumber 106, a vertical coordinate with 19-level resolution which was terrain-following at low levels.

The comprehensive physical parametrisation schemes included shallow and deep (Kuo) convection, a radiation scheme which allowed interaction with model generated clouds and the diurnal radiative cycle.

(Note that before 1 May 1985 for the first four months of the TOGA period ECMWF still operated the T63 model with 16 levels in the vertical.)