Diagnostics of T1279 ECMWF analysis winds in the Mediterranean basin by comparison with ASCAT 12.5 km winds

This article aims to understand to what extent the winds fields from an advanced numerical weather prediction system and from a satellite scatterometer describe the same spatial and temporal features of the wind in the Mediterranean Sea. We investigated wind fields for the period February 2010 to February 2012 using the ASCAT scatterometer data with 12.5 km wind vector cells and the analysis wind fields from the ECMWF T1279 global model. The ASCAT–ECMWF mean relative bias and centred root mean square deviation of wind speed, normalized by scatterometer wind speed w sc , Δ w s /w sc and , have been found to be 7 and 23%. An interesting result is the identification of dependence of both Δ w s /w sc and on the distance from the coast, indicating the coastal areas as the main source of discrepancy between the two datasets. From 50 to 200 km away from coast, decreases from 40 to 25% and Δ w s /w sc from 8 to 4%. These results gain more importance considering that the Mediterranean Sea is essentially a coastal sea (50% of its surface lies within 50 km from the coast). Both Δ w s and have been found to depend nonlinearly on the wind speed. The seasonal variation of Δ w s /w sc and shows that they are in phase opposition, with higher values of during the warm season (April to October). It is hypothesized that local coastal circulations like land/sea breezes could explain the observed mismatch between model and observations. The reported findings emphasize a common feature of the present atmospheric models forecasting winds over regional basins like the Mediterranean. Copyright © 2010 Royal Meteorological Society