Many changes in the operational global data assimilation system of the National Meteorological Center (NMC) during the last few years are reviewed. These changes include: improved physics as well as horizontal and vertical resolution of the global forecast model, an improved quality control and data selection procedure as well as error statistics in an optimum interpolation scheme, and an improved diabatic initialization in the assimilation system. Given these improvements and in preparation for the expected availability of scatterometer vector winds from future satellite missions in the 1990's, several data assimilation and forecast experiments were conducted in the NMC's global data assimilation system using Seasat scatterometer vector winds for a two week period (September 7, 0000 UTC -September, 19 1800 UTC, 1978). The assimilation results show that scatterometer wind data have a positive impact on height and wind analyses over the Southern Hemisphere. Two separate five-days forecasts are made with the initial conditions determined in one case by the assimilation of conventional data in the analysis cycle and in the other both conventional and seven days of scatterometer data. The forecast results show that inclusion of the scatterometer data improves short range weather forecasts, especially over the Southern Hemisphere. Results of the assimilation and forecast experimentsare discussed.

National Weather Service (NWS)

United States