Experiments with perturbed Hirlam analyses based on Singular Vectors

First attempts have been made to perform ensemble forecasting with the Hirlam model. We looked at the convective precipitation in two experiments, carried out in one case study. Perturbations for the analysis were derived from singular vectors computed with the HIRLAM model, and their amplitudes were scaled with the errors of an analysis field from the ECMWF model. The next step was to multiply the singular vectors with random numbers, sampled from a Gaussian distribution, and then the final perturbations were obtained by linearly combining the results.