COMPARISON OF CANADIAN DAILY ICE CHARTS WITH SURFACE OBSERVATIONS OFFNEWFOUNDLAND, WINTER 1992

Forecast ice drift rates and thicknesses displayed on daily ice charts and forecast winds for the Canadian east coast are compared to on-ice observations made during the second Canadian Atlantic Storm Program ( GASP II) of March 1992. Observed and 24-hour forecasts of daily ice dr ift rates were weakly correlated even though long-term means closely m atched observations. Daily drift rates have an RMS error of 13 cm s(-1 ) relative to a 15 cm s(-1) mean 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 pro cesses; and the inconsistency in the methods used by the ice forecaste r. Correlation coefficients between forecast winds and on-ice observed winds decreased from 0.8 at 0-hour to 0.7 for the 30-hour forecast. S imilar results were found between ice drift rates from forecast winds. Histograms of ice thicknesses observed along narrow swaths using a he licopter-towed electromagnetic sensor compared well with undeformed ic e thicknesses representing large areas on ice charts, with differences mainly caused by difference in ice type representation and by co-regi stering the two data sets.