Evaluation of GRAPES Global Ensemble Prediction System (GRAPES-GEPS) of CMA

GRAPES(Global and Regional Assimilation and Prediction System) global ensemble prediction system(GRAPES-GEPS) is a new generation of global ensemble forecasting system being developed by the numerical prediction center of China Meteorological Administration, which is constructed based on the GRAPES-GFS model, using the singular vectors (SVs) as the initial perturbation method, coupled with Stochastic Perturbed Parameterization Tendencies scheme(SPPT). In this paper, the prediction performance of GRAPES-GEPS is given. The evolution characters of initial perturbation and model error of the EPS are emphatically investigated, various verification methods are used to evaluate GRAPES-GEPS performance and its precipitation probability forecast capabilities, and it is also compared with the T639-EPS, which is the current operational EPS of CMA. The results indicate that: 1) The ensemble forecast of GRAPES-EPS outperforms its control forecast; 2) The spread of ensemble members of GRAPES-EPS is smaller than error of the model obviously; 3) The SPPT scheme can visibly improve the model’s ability in precipitation probability forecast; 4) Compared with the T639-EPS, although the resolution of GRAPES-EPS is lower at present, the miss probability of forecast is obviously reduced due to the increased ensemble size.