Four-Dimensional Data Assimilation of Gale Data Using a Multivariate Analysis Scheme and a Mesoscale Model with Diabatic Initialization
NAVAL RESEARCH LAB WASHINGTON DC
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A method of assimilating 3-hourly sounding data is developed and successfully tested in this study. First, the successive corrections scheme of Bratseth 1986 which converges to optimum interpolation, is applied for the numerical analysis of data collected during the Genesis of Atlantic Lows Experiment GALE. Next, diabatic forcing is incorporated into a vertical mode initialization scheme to provide more realistic initial conditions and to shorten the spinup time of the Naval Research LaboratoryNorth Carolina State University NRLNCSU mesoscale mode. Latent-heating profiles are computed from spun-up model-generated and observed rainfall. Finally, the multivariate, successive correction analysis scheme correction analysis scheme and the diabatic initialization procedure are combined with the NRLNCSU model to form an intermittent data-assimilation system. Assimilations of the GALE data over a 2 12-day period were performed with differing update cycles of 3, 6, and 12 h. Twelve-hour NMC hemispheric analyses served as the no assimilation control case for comparison. The assimilation of 3-hourly GALE data led to large decreases in background forecast rms errors and smaller decreases in analysis rms error. Rainfall prognoses from the assimilated states showed much more rapid spinup and better overall patterns than did the no assimilation precipitation forecasts.