Wildfires as a source of airborne mineral dust – Revisiting a
conceptual model using Large-Eddy simulations (LES)
Abstract. Airborne mineral dust is a key player in the Earth system and shows manifold of impacts on atmospheric properties such as the radiation budget and cloud micro-physics. Investigations of smoke plumes originating from wildfires found significant fractions of mineral dust within these plumes – raised by strong turbulent winds related to the fire. The present study revisits the conceptual model describing the emission of mineral dust particles during wildfires by pyro-convection as described by the literature. This is achieved by means of high resolved Large-Eddy simulations (LES), conducted with the All Scale Atmospheric Model (ASAM). The impact of different fire properties representing typical grassland and shrubland fires, and different ambient atmospheric conditions on the fire-driven winds and their capability to mobilize mineral dust particles were investigated. Results from this study illustrate that the energy release of the fire leads to a strong increase in strength and frequency of occurrence of intense near-surface winds, which exceed typical threshold velocities inevitably required for dust emissions. The fire-induced modulations of the wind field can be transported up to some kilometers downstream of the fire area and are able to favor dust emissions also in some distance to the fire area. Although measurements showed already the importance of wildfires on dust emissions, pyro-convection is so far neglected as a dust emission process in atmosphere-aerosol models. The results presented in this study can be seen as the first step towards a systematic parameterization representing the connection between typical fire properties and related dust emissions, which eventually can be implemented in larger-scale aerosol models ultimately contributing to the reduction of uncertainties in the aerosol-climate feedback.