Application of Stochastic Parameter Perturbations in SL-AV Model Version for Long-range Forecasts

The paper examines the impact of applying the parameter perturbations for schemes describing sub-grid scale processes in the SL-AV atmosphere model on characteristics of monthly mean atmospheric circulation in ensemble subseasonal forecasts. 25-year retrospective forecasts are computed for different seasons with different perturbation sets, and the results are compared with the forecasts without perturbations. It is shown that perturbing just three parameters reduces forecast errors of some variables as compared to unperturbed forecasts without introducing errors into integral characteristics.