Operational analysis are affected by major changes in models, analysis technique, asimilation and observation usage, which are an essential product of research and progress.
The ECMWF (European Centre for Medium-Range Weather Forecasts) performed a consistent re-analysis of atmospheric data using a "frozen" production system. The ECMWF Re-Analysis (ERA) Project produced a new, validated 15 year dataset of assimilated data for the period 12/1978-02/1994.
The assimilation scheme consisted mainly of the Integrated Forecast System (IFS) version of the ECMWF forecast model with T106 resolution on 31 vertical hybrid levels. An intermitted statistical (optimum interpolation) analysis with 6 hour cycling was performed. It includes a diabatic, non-linear normal mode initialisation (5 vertical modes).
This data set (T106 resolution) consists of an initialized surface field which is stored in 6h-intervals (0,6,12,18).