Definition of Class 1-4 metrics for the Arctic

This document aims to describe sea-ice metrics. Metrics types are: • Class1: Standard model products 2D and 3D interpolated fields on a regular polar stereographic grid • Class2: Other model products 2D fields along sections, 1D tables at point locations. • Class3: derived quantities computed on a daily basis. • Class4: derived quantities to assess model performance, computed on a weekly basis The document describes the metrics to be used for Arctic forecast products and should be used by people willing to contribute to and access the Arctic TEP, which is organized following the data management specified in MERSEA. The goal is to assess the present forecasting systems. Three criteria families have been identified: • Consistency: verifying that the system outputs are consistent with the current knowledge of the ocean circulation and climatologies. • Quality: quantifying the differences between the system best results (analysis) and the sea truth, as estimated from observations, preferably using independent observations (not assimilated). • Performance (or accuracy): quantifying the short term forecast capacity of each system, i.e. answering the questions do we perform better than persistency? better than climatology?NERSC Technical Report no. 301. Funded by EU FP6 through the MERSEA Integrated Project