Multi-Model Simulations of a Mediterranean Extreme Event: Impact of Mineral Dust on VAIA Storm

In this study, multi-model simulations are performed in fully-coupled configurations for investigating the effect of desert dust on spatial-temporal variation of precipitation. Dust-based processes of formation/removal of ice nuclei (IN) and cloud condensation nuclei (CCN) are investigated by using both on-line access model WRF-CHIMERE and online integrated model WRF-Chem. The comparisons of models’ predictions with measured (GRISO: Spatial Interpolation Generator from Rainfall Observations) precipitations over Italian Peninsula, point out the models’ skills in reproducing at least the severe orographic precipitations occurred over the alpine areas. To quantify the impact of the mineral dust transport concomitant to the Atmospheric River (AR) on cloud formation, a sensitivity study is performed by using WRF-CHIMERE model (i) by zeroing dust concentrations, and (ii) by modifying the Thompson Aerosol-Aware microphysics scheme setting (i.e. DeMott 2015). Our findings show that, although important instantaneous changes are modelled at local scale for precipitation and for temperature, not significant total changes in precipitation and air temperature averaged over the whole domain are pointed out by sensitivity test. On the other hand, the WRF/Chem simulation differs from WRF-CHIMERE in temporal-spatial variability of dust concentrations and precipitations.