Description of the upgrade

ECMWF introduced a 3-dimensional variational (3D-Var) analysis scheme. 3D-Var is a new code for the analysis of model-level values of temperature, vorticity, divergence and specific humidity, and surface pressure. Minor changes to the forecast model were implemented at the same time.
On average, forecasts from 3D-Var for the Northern Hemisphere are of similar quality as forecasts from the previous Optimum Interpolation system, while forecasts for the southern hemisphere tend to exhibit higher skill. In addition, 3D-Var gives generally better temperature verification results, especially at low levels and in the stratosphere, and better wind scores at 200 hPa and above.
The analysis and prediction of tropical cyclones appear to have improved with 3D-Var.

Implemented: 30 January 1996  


ECMWF Newsletter: Please see article "3D-Var - the new operational analysis scheme" from the ECMWF Newsletter No.71