Production of a new, validated 15 year data set of assimilated atmospheric 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. The data sets (T106 resolution) consist of model level fields which are stored in 6h-intervals (0,6,12,18). These are the 31 model level hybrid co-ordinates: The vertical coordinate parameters define the edges of the atmospheric layers in terms of the surface pressure (in Pascals). The parameters can be considered as being true at the mid-point (in pressure) of a layer for each point. The values are: A(I) B(I) 1 0.000000 0.0000000000 2 2000.000000 0.0000000000 3 4000.000000 0.0000000000 4 6000.000000 0.0000000000 5 8000.000000 0.0000000000 6 9976.135361 0.0003908582 7 11820.539617 0.0029197006 8 13431.393926 0.0091941320 9 14736.356909 0.0203191555 10 15689.207458 0.0369748598 11 16266.610500 0.0594876397 12 16465.005734 0.0878949492 13 16297.619332 0.1220035886 14 15791.598604 0.1614415235 15 14985.269630 0.2057032385 16 13925.517858 0.2541886223 17 12665.291662 0.3062353873 18 11261.228878 0.3611450218 19 9771.406290 0.4182022749 20 8253.212096 0.4766881754 21 6761.341326 0.5358865832 22 5345.914240 0.5950842740 23 4050.717678 0.6535645569 24 2911.569385 0.7105944258 25 1954.805296 0.7654052430 26 1195.889791 0.8171669567 27 638.148911 0.8649558510 28 271.626545 0.9077158297 29 72.063577 0.9442132326 30 0.000000 0.9729851852 31 0.000000 0.9922814815 32 0.000000 1.0000000000 where the pressure values are A(I) + B(I) * SurfacePressure The pressure for the middle of the layers (where the modell data are calculated) can be obtained by simple linear interpolation in p. p(i+1/2) = 1/2 * (p(i)+p(i+1))