Impact of WIVERN Wind Observations on ARPEGE Numerical Weather Prediction Model Forecasts Using an Ensemble of Data Assimilation Method

To fill the gap of in-cloud wind observations in the global observing system, the European Space Agency selected the wind velocity radar nephoscope (WIVERN) mission as one of the Earth Explorer 11 candidate missions to enter Phase A in 2023. WIVERN, with its dual-polarisation Doppler conically scanning W-band radar, will be the first space-based mission to provide in-cloud horizontal line-of-sight (HLOS) winds at a fine vertical resolution of 650 m sampling and a broad swath of width 800 km. We report on the impact of WIVERN simulated HLOS winds to improve global numerical weather prediction (NWP) model forecasts, using an ensemble of data assimilation (EDA) approach. In this methodology, the benefits of adding WIVERN simulated HLOS wind observations to the current observing system are measured by their ability to reduce the EDA spread at a given forecast lead time. The operational EDA system of the global NWP model ARPEGE (Action de Recherche Petite Echelle Grande Echelle) is used for a 1-month period in 2021. Results indicate that WIVERN HLOS will not only significantly improve the uncertainty of the wind forecasts throughout the entire troposphere, but also of the temperature and humidity fields. This positive impact is particularly seen in the midlatitudes. Results of this study also highlight the strong vertical complementarity between WIVERN, Aeolus (Doppler wind lidar), and atmospheric motion vectors observations. Finally, the impact of WIVERN is also studied in synergy with the EUMETSAT follow-on EPS-Aeolus mission, and results demonstrate that the two active wind satellite missions would vertically complement each other as they provide wind observations at different altitudes, and in different meteorological areas.