High‐resolution simulation over central Europe: assimilation experiments during COPS IOP 9c

Abstract

AbstractThe impact of assimilating conventional and Global Positioning System (GPS) Zenith Total Delay (ZTD) data over France into the Weather Research and Forecasting (WRF) model is investigated during COPS IOP 9c. A convection‐permitting horizontal resolution of 3.6 km covering the whole of central Europe was chosen. Four different simulations were conducted to show the influence of assimilating different observation types on the forecast. Additionally, a comparison with the models COSMO‐DE and COSMO‐EU from the German Meteorological Service (DWD) was performed.The results show a clear positive impact of assimilating data into a convection‐permitting configuration of the WRF model over Europe. The additional assimilation of GPS‐ZTD data shows a further improvement of integrated water vapour (IWV) correlation, but the influence on prediction of precipitation was not necessarily clear. A comparison with radiosonde data shows a positive impact on the humidity structure after 12 hours, while an overestimation of precipitation still remains.A further comparison with the operational high‐resolution models of DWD during this COPS IOP reveals a strong dependence on the initial boundary‐layer wind field especially as the near‐surface wind field is better represented in the ECMWF analysis than in the COSMO analysis.As this is, to our knowledge, the first study applying a convection‐permitting configuration of WRF over Europe, it can be used as a guidance for further studies. Copyright © 2011 Royal Meteorological Society