Comparison of ERS and Nscat scatterometer for ocean applications under very high wind conditions

With the availability of scatterometer data, initially in 1978 with Seasat, followed by the ERS mission for more than seven years since 1991 and Nscat for nine months in 1997, the number of derived wind observations over the world oceans has radically increased especially over the Southern Oceans. Whereas before there were only sparse measurements from ships, the scatterometer instrument provides data with a 25 or 50 km horizontal resolution covering most of the ocean surface in 2-3 days. Not only the quantity, but also the quality of the wind observations over the oceans has improved, as it has been demonstrated that scatterometer winds have a slightly higher quality than ship measurements. Scatterometer winds guarantee global, long-term monitoring of the winds on the oceans, which make them very valuable for climate studies although they have not yet been fully exploited in this area. Primary users of scatterometer data are NWP Centres and Oceanographic Institutes who are assimilating the scatterometer derived wind in their atmospheric, wave and ocean general circulation models. In particular in the Southern Hemisphere, where only few conventional wind observations exist, the introduction of these scatterometer-derived winds has led to a significant improvement of the model analyses and, to a somewhat lesser extent, of the forecast