TY - CPAPER AU - B. Farrell AU - P.J. Ioannou BT - Seminar on Recent developments in data assimilation for atmosphere and ocean, 8-12 September 2003 CY - Shinfield Park, Reading DA - 2003 LA - eng PB - ECMWF PP - Shinfield Park, Reading PY - 2003 SP - 369 EP - 392 T2 - Seminar on Recent developments in data assimilation for atmosphere and ocean, 8-12 September 2003 TI - Approximating optimal state estimation ER -