TY - RPRT AU - Franco Molteni CY - Shinfield Park, Reading DA - 01/1987 LA - eng M1 - 61 M3 - Technical Report PB - ECMWF PP - Shinfield Park, Reading PY - 1987 EP - 36 TI - Empirical orthogonal function analysis in the zonal and eddy components of 500 mb height fields in the Northern extratropics ER -