Forecast ice drift rates and thicknesses displayed on daily ice charts and forecast winds for the Canadian east coast are compared to on#x2010;ice observations made during the second Canadian Atlantic Storm Program (CASP II) of March 1992. Observed and 24#x2010;hour forecasts of daily ice drift rates were weakly correlated even though long#x2010;term means closely matched observations. Daily drift rates have an RMS error of 13 cm s#x2010;1relative to a 15 cm s#x2010;1mean in addition to an RMS direction error of 50 degrees. Contributions towards daily drift uncertainties were: the estimation of winds, unmodelled physics of ocean and ice cover processes; and the inconsistency in the methods used by the ice forecaster. Correlation coefficients between forecast winds and on#x2010;ice observed winds decreased from 0.8 at 0#x2010;hour to 0.7 for the 30#x2010;hour forecast. Similar results were found between ice drift rates from forecast winds. Histograms of ice thicknesses observed along narrow swaths using a helicopter#x2010;towed electromagnetic sensor compared well with undeformed ice thicknesses representing large areas on ice charts, with differences mainly caused by difference in ice type representation and by co#x2010;registering the two data sets.
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