COAMPS® ocean ensemble forecast

The development of COAMPS Ocean Ensemble Forecast System is currently underway at Naval Research Laboratory in Monterey. The system is based on the Ensemble Transform Kalman Filter (ETKF) algorithm. The initial ensemble perturbation fields are generated by perturbing a mean of one month ocean forecasts. The perturbed atmospheric forcing fields are produced using a time deformation, a new technique, of a single COAMPS atmospheric forcing. A transformation matrix is used to transform forecast perturbations to analysis perturbations. This matrix is obtained by solving the error covariance update equation for an optimal data assimilation scheme within the ensemble perturbation subspace. The ocean ensemble forecast is set for a 24-h update cycle with 20 ensemble members. The COAMPS ocean ensemble forecast system is tested using extra observations from the Autonomous Ocean Sampling Network II (AOSN II) Monterey Bay area. The ETKF ensemble mean and the ensemble estimated forecast error variance are examined.