The system is based on the ocean circulation HAMSOM model and on the harmonical prediction of tides computed from data measured by the tide gauge network REDMAR, managed by Puertos del Estado. At this moment, HAMSOM is running barotropic and vertically integrated within Nivmar.

Nivmar is executed twice a day using the output from the INM application of HIRLAM. Data from REDMAR tide gauges is used, allowing the system to correct systematic errors in the means sea level due to physicals processes that are not included in the ocean model (i. e. steric height). The forecast horizon is 48 hours.

The system was tested during a benchmark period (November 95 to March 96) with data from the PROMISE data set. Results from this experiment show that Nivmar is able to correctly predict sea level.

This plots shows the residuals (difference between sea level and harmonical predictions) predicted by Nivmar at La Coruña during the whole period. The forecast horizon is 48 hours. The plot shows a comparison of the measurements of the tide gauge and the data predicted by Nivmar 48 hours before the measurement was taken.

The following table shows the results from a statistical comparison of both series.

being Nr the number of records, Xm and Ym are the mean values of the measured and simulated series, RMSE is the Root Mean Square Error, RMAX is the largest error, m and b are the slope and the interception and IC is the correlation index.