TESTS OF DATA ASSIMILATION AND DATA INITIALIZATION FOR THE PURPOSES OF SHORT-RANGE WEATHER FORECAST

The initialization and assimilation of input data were studied and tes ted by the adiabatic version of a simple numerical model for short-ran ge weather forecast. The initialization was based on the utilization o f a digital filter technique. The method succeeded in removing high-fr equency oscillations from prognostic pressure fields. However, excessi ve smoothing deteriorated the accuracy of the prediction at the lowest levels of the atmosphere. The data assimilation was performed using t he nudging method. Three versions of the nudging method in a splitting scheme were tested. The inclusion of the assimilation at the end of t he integration step proved to be the best. The assimilation damped the oscillations of prognostic surface pressure fields and slightly impro ved the pressure prediction at the lowest levels of the atmosphere.