Study of Stochastically Perturbed Parameterization Tendencies in West China Mountains Convective-Scale Ensemble Forecast
To investigate the influence of stochastically perturbed parameterization tendencies (SPPT) on convective-scale ensemble prediction under complex topography conditions, sensitivity experiments were conducted on three parameters of SPPT random perturbed field, including temporal scale, spatial scale and grid standard deviation, to explore its prediction effect. The results showed that the SPPT built with the parameters of 90 km spatial scale, 3 h time scale and 0.525 grid standard deviation performed best in this case. The spreads of upper-air physical quantities (zonal wind field, temperature field and humidity field) and near-surface physical quantities (10 m wind and 2 m temperature) increase rapidly. The spread/RMSE that considers prediction errors is also better than other experiments. Although the ensemble mean of 3 h accumulated precipitation is not significantly improved at all categories compared with other experiments, the ETS scores of precipitation grades ≥10 mm, ≥25 mm and ≥50 mm are close to or higher than those of the control experiment, and the probability prediction skills are better. On the whole, the influence of spatial scale parameter on spread is more obvious than that of time scale. The increase of perturbation amplitude plays a positive role in increasing spread, and meanwhile can improve the probability prediction skills of precipitation different magnitudes.