Lagrangian validation of numerical drifter trajectories using drifting buoys:Application to the Agulhas system

摘要

The skill of numerical Lagrangian drifter trajectories in three numerical models is assessed by comparingthese numerically obtained paths to the trajectories of drifting buoys in the real ocean. The skill assess-ment is performed using the two-sample Kolmogorov-Smirnov statistical test. To demonstrate theassessment procedure, it is applied to three different models of the Agulhas region. The test can eitherbe performed using crossing positions of one-dimensional sections in order to test model performancein specific locations, or using the total two-dimensional data set of trajectories. The test yields four quan-tities: a binary decision of model skill, a confidence level which can be used as a measure of goodness-of-fit of the model, a test statistic which can be used to determine the sensitivity of the confidence level, andcumulative distribution functions that aid in the qualitative analysis. The ordering of models by their con-fidence levels is the same as the ordering based on the qualitative analysis, which suggests that themethod is suited for model validation. Only one of the three models, a 1/10° two-way nested regionalocean model, might have skill in the Agulhas region. The other two models, a 1/2° global model and a1/8° assimilative model, might have skill only on some sections in the region.