Accuracy of Surface Geostrophic Wind Forecasts in the Central Arctic

Abstract

Statistics of surface and 1000 mb geostrophic winds from the central Arctic are estimated from 18 months of daily analyses and National Meteorological Center numerical forecasts in 1979 and 1980. The data base for the analyses and forecasts includes pressure measurements at an array of drifting buoys that resolves wind variations on scales as small as 500 km over much of the ice-covered ocean. The time mean wind has a typical speed of 2 m s?1, while fluctuations are about 8 m s?1. Linear models are estimated that make optimal use of the numerical forecasts over 24, 48 and 72 hours for predicting the observed wind fluctuations. At all three lags the optimal predictions exhibit substantial skill over persistence forecasts. Typical residual errors at the three lags are 4.2, 5.3 and 6.5 m s?1, and are similar to corresponding residuals at an arbitrary midlatitude site surrounded by many more upper air and surface stations than exist in the central Arctic. The arctic winds are more persistent than those at the midlatitude site, so the improvement of the NMC forecasts over persistence is smaller in the Arctic. Arctic residual errors at 24 and 48 h ;lags are sufficiently small to warrant application of these forecasts to prediction of short-term sea ice movements on a routine basis.