Spatial scales of marine surface wind for scatterometer calibration

During the last experiment of the IFREMER TOSCANE program, an array of wind buoys and a mast were deployed at sea, together with a ship, in order to investigate the accuracy of wind-buoy measurements and wind fluctuations at spatial scales of 25 km to 50 km, comparable to ERS-1 scatterometer measuring cells. Temporal and spatial scales of wind fluctuations were investigated within the range of interest for scatterometer. The level of high frequency variability of buoy measurements is shown to vary from one buoy to another ; it becomes homogeneous as soon as the data are averaged over at least 10 mn. The variance of wind differences between two locations is studied as a function of averaging time and separation distance. Major characteristics of spatial wind coherences are also given.