3D-mask for the ETR Initialization in the NCEP Global Ensemble Forecast System
Based on the preliminary study, a rescaled distribution of initial perturbations is very important for the performance of ensemble forecast. Therefore, there is significant difference for the ET_2DR and ET_3DR initial perturbations. Relative to the ET_2DR, the horizontal distribution of the ET_3DR initial perturbations at 500hPa is more correlated to the baroclinic instability over the extra-tropic of the Northern Hemisphere and connected with the deep convection over the tropics. Furthermore, the maximum value of vertical distribution for the ET_3DR initial perturbations corresponds to the subtropical jet region and tropical easterlies jet region. Naturally, due to the better representation of horizontal and vertical structures of initial perturbations for the ET_3DR, the ensemble spread (or uncertainty) grows much faster than the ET_2DR, especially at the lower levels and over the tropics.