Comment on amt-2022-311

Abstract

To detect global wind profiles and improve numerical weather prediction (NWP), the European Space Agency (ESA) launched the Aeolus satellite carrying a space-borne Doppler Wind Lidar in 2018. After the successful launch, the European Centre for Medium-Range Weather Forecasts (ECMWF) performed the observing system experiments (OSEs) to evaluate the contribution of Aeolus data to NWP. This study aims to assess the impact of Aeolus wind assimilation in the ECMWF model on surface wind forecast over tropical ocean regions by taking buoy measurements for reference and over high latitude regions by taking weather station data for reference for the year 2020. The assessments were conducted through inter-comparison analysis and triple collocation analysis. The results show that with Aeolus data assimilation, the tropical sea surface wind forecast could be slightly improved at some forecast time steps. The random errors of u (zonal) and v (meridional) wind components from OSEs are within 1 m s-1 with respect to the model resolution. For the high latitude regions, Aeolus can reduce the wind forecast errors in the Northern Hemisphere with forecast extending, particularly during the first half-year of 2020 and during the winter months. For the Southern Hemisphere, the positive impact is mainly found for the u component at most forecast steps during June, July and August. Moreover, compared with the tropical ocean regions and the region > 60° N, the random error of OSEs for the region > 60° S increases significantly to 3 m s-1 with forecast extending. Overall, this study demonstrates the ability of Aeolus winds to improve surface wind forecast over tropical oceans and high latitude regions, which provides valuable information for practical applications with Aeolus data in the future.