Miller, A. J. and B. D. Cornuelle, 1999:

**
Forecasts from fits of frontal fluctuations**

*Dynamics of Atmospheres and Oceans,***29**,
305-333.

**Abstract.**
A primitive equation ocean model is fit with strong constraints to non-synoptic hydrographic surveys in an unstable
frontal current region, the Iceland-Faeroe Front. The model is first initialized from a time-independent objective analysis
of non-synoptic data (spanning 2 to 6 days). A truncated set of eddy-scale basis functions is used to represent the initial
error in temperature, salinity, and velocity. A series of model integrations, each perturbed with one basis function for one
dependent variable in one layer, is used to determine the sensitivity to the objective-analysis initial state of the match to
the non-synoptic hydrographic data. A new initial condition is then determined from a generalized inverse of the
sensitivity matrix and the process is repeated to account for nonlinearity. The method is first tested in `identical twin'
experiments to demonstrate the adequacy of the basis functions in representing initial condition error and the convergence
of the method to the true solution. The approach is then applied to observations gathered in August 1993 in the
Iceland-Faeroe Front. Model fits are successful in improving the match to the true data, leading to dynamically consistent
evolution scenarios. However, the forecast skill (here defined as the variance of the model-data differences) of the model
runs from the optimized initial condition is not superior to less sophisticated methods of initialization, probably due to
inadequate initialization data. The limited verification data in the presense of strong frontal slopes may not be sufficient to
establish forecast skill, so that it must be judged subjectively or evaluated by other quantitative measures.

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