Assessing the impact of Aeolus wind data assimilation on the Saharan dust simulations in the framework of the JATAC campaign

Throughout the year, the Tropical Atlantic Ocean receives constantly enormous amounts of mineral particles emitted over the western Sahara. Despite the numerous efforts, the current state-of-the-art atmospheric-dust models are not yet able to represent adequately the Saharan dust outflows towards the Atlantic Ocean. Several drawbacks in the relevant parameterization schemes can explain this deficiency, which subsequently hampers an optimal assessment of the dust-induced impacts. One of these aspects is the wind acting as the driving force of dust emission and transport. Thanks to the deployment of the ALADIN (Atmospheric Laser Doppler Lidar) lidar, onboard the European Space Agency (ESA) Aeolus satellite, profiles of HLOS (Horizontal Line-Of-Sight) winds are acquired globally up to a maximum of 30 km altitude. This unique global dataset is filling an existing observational gap in the Tropics, among other regions of the planet. In addition, the assimilation of Aeolus HLOS winds has revealed an improvement in numerical weather predictions (NWP), particularly in the Tropics where the major portion of the global dust budget resides.

The improvements of NWP are expected to also advance dust numerical simulations. Such hypothesis is under investigation in the NEWTON (ImproviNg dust monitoring and forEcasting through Aeolus Wind daTa assimilatiON) project funded by ESA under the Aeolus+Innovation framework. To address the NEWTON scientific objective, short-term regional dust forecasts, relying on the WRF model operating at the National Observatory of Athens (NOA), are conducted. More specifically, two WRF runs are performed using boundary and initial conditions from the ECMWF IFS (Integrated Forecasting System) outputs, produced with (hel4) and without (hel1) the assimilation of Aeolus quality screened Rayleigh-clear and Mie-cloudy wind profiles. Our simulation domain encompasses most part of the Sahara Desert and the Atlantic Ocean, bounded between the Equator and mid-latitudes. Focus is given on September 2021, when the JATAC (Joint Aeolus Tropical Atlantic Campaign) campaign took place in Cape Verde providing reference observations (ground-based, airborne) valuable for a comprehensive evaluation of WRF dust-related outputs. The assessment analysis is further extended by utilizing the satellite dust datasets MIDAS (ModIs Dust AeroSol) and LIVAS (LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies), both developed at NOA, providing columnar dust optical depth and vertical profiles of dust extinction, respectively. Finally, all the NEWTON related activities are disseminated via the official website (https://newton.space.noa.gr) and the EO4Society portal (https://eo4society.esa.int/).