Mediterranean Forecasting System: forecast and analysis assessment through skill scores
[摘要] This paper describes the first evaluation of the quality of the forecast andanalyses produced at the basin scale by the Mediterranean ocean ForecastingSystem (MFS) (
http://gnoo.bo.ingv.it/mfs). The system producesshort-term ocean forecasts for the following ten days. Analyses are producedweekly using a daily assimilation cycle. The analyses are compared withindependent data from buoys, where available, and with the assimilated databefore the data are inserted. In this work we have considered 53 ten daysforecasts produced from 16 August 2005 to 15August 2006.
The forecast skill is evaluated by means of root mean square error (rmse)differences, bias and anomaly correlations at different depths fortemperature and salinity, computing differences between forecast andanalysis, analysis and persistence and forecast and persistence. The SkillScore (SS) is defined as the ratio of the rmse of the difference betweenanalysis and forecast and the rmse of the difference between analysis andpersistence. The SS shows that at 5 and 30 m the forecast is always betterthan the persistence, but at 300 m it can be worse than persistence for thefirst days of the forecast. This result may be related to flow adjustmentsintroduced by the data assimilation scheme. The monthly variability of SSshows that when the system variability is high, the values of SS are higher,therefore the forecast has higher skill than persistence.
We give evidence that the error growth in the surface layers is controlledby the atmospheric forcing inaccuracies, while at depth the forecast errorcan be interpreted as due to the data insertion procedure. The data, both insitu and satellite, are not homogeneously distributed in the basin;therefore, the quality of the analyses may be different in different areasof the basin.
