Vegetation fires as a source of soil-dust particles – a global model perspective

Vegetation fires are well known as an important source of aerosol particles originating from the combustion of carbonaceous material. Much less known is that these fires can also efficiently inject soil-dust particles into the atmosphere, raised by the strong fire-induced winds. These soil-dust particles and the likely co-emitted biogenic particles are potent cloud condensation nuclei (CCN) and ice nucleating particles (INPs), and can substantially alter the cloud microphysics and thus impact the Earth’s radiation budget. Fires are an integral component of the Earth system that affect different landscapes around the globe. As they are supposed to get more frequent and more severe along with the ongoing global warming, a better knowledge of these specific fire emissions is crucial to understand their impacts on weather and climate.

Therefore, this work investigates the potential of wildfires to emit soil-dust particles on a global scale as a part of the newly established Leibniz ScienceCampus “BioSmoke” (‘smoke and bioaerosols in a changing climate’). As this particular dust emission pathway is not considered by the state-of-the-art dust emission models, a parameterization describing fire-induced dust emission fluxes has been developed and implemented into the global aerosol-climate model ICON-HAM. Fire-dust emissions are modelled as a function of the fire radiative power (FRP), the ambient wind conditions, and further soil-surface properties, including the soil type and a vegetation-dependent surface roughness correction.

Multi-year ICON-HAM simulations have revealed that fire-related dust emissions can account for up to one fifth of the total global dust emissions with strong regional and seasonal variations, both as the result of a varying fire activity and the local soil-surface conditions that can foster or impede also fire-dust emission significantly. In regions where the classic wind-driven dust emissions from arid, unvegetated soil surfaces are rather low but wildfires occur frequently, e.g., in large parts of the Southern hemisphere, fire-related dust emissions can add substantially to the atmospheric aerosol load and affect the local radiation budget there.