Global data assimilation experiments with scatterometer winds from SEASAT-A

Two days of global scatterometer-derived oceanic surface winds during the period of 0000 GMT 16 July-0000 GMT 18 July 1978 from the SEASAT-A satellite are used in the NMC's global data assimilation and forecast experiments to gain a preliminary appreciation of the impact of this dataset. The NMC's global data assimilation system used in this study is described. The nature of the scatterometer winds and their error characteristics are discussed. Two parallel 48-hour data assimilation experiments are conducted: one including scatterometer wind data (SASS), the other without (NOSASS). After 48 hours of assimilation, large differences have evolved between SASS and NOSASS analyses due to the scatterometer winds. Comparison of the analyses with the operational analysis generated by the Australian Bureau of Meteorology suggests that the influence of scatterometer winds was beneficial in the Southern Hemisphere.