Demonstration of Comparison Methods for Ocean Model Validation

In recent years an increasing amount of oceanographic data has become available. This includes observations as well as data from hydrodynamic ocean models. Validation is required for establishing the necessary confidence in new sources of data. Generally ocean models and other data sources such as satellite imagery are validated by comparing the output to conventional observations or the output of established ocean models. Methods of comparison used in literature range from refined statistical methods to comparisons of snapshots. This work collects descriptions of some of the most widely used comparison methods. The capabilities and limitations of each method are demonstrated using examples from modelled and observed oceanographic data. The work has a particular focus on how to determine discrepancies on vertical gradients in the oceanographic parameters since acoustic propagation is sensitive to errors in the sound speed gradient.