EnKF-C user guide
  EnKF-C provides a compact generic framework for off-line data assimilation into large-scale layered geophysical models with the ensemble Kalman filter (EnKF). It is coded in C for GNU/Linux platform and can work either in EnKF, ensemble optimal interpolation (EnOI), or hybrid (EnKF/EnOI) modes. 
Pavel Sakov
cs.CE