Impacts of Different Background Error Samples Simulation Schemes on Numerical Forecast—Taking Typhoon "Soudelor" (1513) as an Example

With WRF (Weather Research and Forecasting Model), WRF-3DVAR (Weather Research and Forecasting-Three-Dimensional Variational Data Assimilation) and NMC (National Meteorological Center) method, it is investigated whether or not and how the statistical background error samples under different initialization schemes have not-neglected impacts upon the background error covariance and its related forecasts. The experiments with hot-start cycled assimilation and cold-start initialization schemes are carried out. The results indicate that, the single observation idealized assimilation experiments with background error covariance calculated from statistical background error samples under different initialization schemes are consistent with theoretical model. The differences between analyzed incremental fields are obvious and should not be ignored. The experimental results of “Soudelor” (1513) typhoon rainfall event in 2015 indicate that the background error covariance calculated from background error samples under different initialization schemes has a certain effect on the assimilation analyzed fields, and exerts obvious effects on the forecasts of typhoon track and rainfall, but have little impacts on the typhoon intensity and maximum wind speed near typhoon center. Numerical experiments with four different initial time indicate that the background error covariance calculated from background error samples under hot-start cycled assimilation schemes shows a much better forecast for "Soudelor" typhoon track and rainfall, and its impacts on typhoon track is mainly after 24-h numerical forecast model integration.