Robert Wagner

Mineral dust is a key component of the globally-emitted aerosol mass. Although, mineral dust mixes with anthropogenic pollution during its atmospheric lifetime, data on polluted mineral dust layers have been scarce.In April 2017, the A-LIFE aircraft field experiment (www.a-life.at) was carried out in the Eastern Mediterranean. A-LIFE combined ground-based, airborne, satellite, and modelling efforts to characterize mineral dust mixtures with unprecedented detail. In 22 research flights (~80 flight hours), outbreaks of Saharan and Arabian dust, as well as pollution, biomass burning, and dust-impacted clouds were studied, and a unique aerosol and cloud data set was collected. Aerosol source apportionment was achieved with the Lagrangian transport and dispersion model FLEXPART version 8.2. Based on FLEXPART model results and aerosol measurements, the observations were classified into 12 aerosol types consisting of four main aerosol types (Saharan dust, Arabian dust, mixtures with and without coarse mode). Each of the four main aerosol types was further separated into three sub-classes (clean, moderately-polluted and polluted). For each of the 12 aerosol classes, microphysical and optical aerosol properties were derived.For the first time, the effect of pollution on the microphysical and optical properties of Saharan and Arabian dust was investigated systematically, revealing significant changes as a function of pollution content. The particle size distribution changes as a function of pollution content with effective diameters systematically decreasing for increasing pollution content. The collected data also provide new insights into the impact of Saharan and Arabian dust on cloud evolution processes, atmospheric radiation budget, and local meteorology. One outstanding finding of A-LIFE is that scattering properties of polluted dust mixtures do not show the typical dust signature, but rather show a wavelength-dependency of the scattering coefficient which is typical for pollution. This means that optical properties of mineral mixtures are frequently dominated by the pollution.In this presentation, we will show the results of the A-LIFE project including its mission objectives, experimental design, and meteorological conditions; highlight major A-LIFE findings; and feature the available data products on the optical, microphysical, and hygroscopic properties of pure and polluted mineral dust.

Vegetation fires emit a wide variety of aerosol particles. Most originate from the combustion of carbonaceous material, however, fire-induced pyro-convective updrafts can modify the near-surface wind field in a way that mobilizes soil-dust particles from the ground and inject them into the atmosphere. Mineral dust particles are well known as efficient cloud condensation nuclei (CCN) and ice nucleating particles (INPs), thereby substantially altering cloud microphysics and influencing the Earth’s radiation budget through scattering and absorption of solar radiation. When emitted during wildfires, these dust particles are likely mixed with smoke aerosols, which modifies their physio-chemical properties and consequently their impacts on the atmosphere and climate. Therefore, a precise characterization of this emission pathway and robust knowledge of its global abundance are essential.The fire-driven emission of soil-dust particles has already been incorporated into the global aerosol–climate model ICON-HAM through the development of a sophisticated parameterization that describes fire-induced dust emission fluxes as a function of fire intensity and some soil-surface properties, such as the soil type and the vegetation class at the fire location. Multi-year model simulations have indicated that fire-related dust emissions can account for a significant fraction of the global atmospheric dust load, exhibiting strong regional and seasonal variability driven by a varying fire activity and the local soil-surface conditions.However, global fire activity has changed substantially over the recent decades due to both climatic and socioeconomic factors, resulting in significant shifts in the magnitude and regional distribution of fire-related dust emissions. Here, trends in fire-induced dust emissions over the past 20 years are analyzed and changes across different continental regions are contrasted. Furthermore, projections of fire activity under future climate scenarios can be used to assess the strength and regional distribution of fire-related dust emissions under changing climate conditions and mitigation strategies. This analysis can contribute to improved estimates of the future global aerosol burden, in particular with respect to the changing fire occurrence in a warmer world.

Dust aerosols are a key component of the Earth's climate system. However, global climate models often depict mineral dust as a uniform aerosol. This simplification limits the physical realism of dust simulations, necessitating comparison with available observations to determine whether mineralogical variability is accurately represented when incorporated into a global climate-aerosol model.In this study, we examine how well a mineralogical soil database translates into realistic mineral-resolved dust transport and deposition in the global climate model ICON coupled with the aerosol module HAM. This implementation is based on the mineralogical soil database of Journet et al. (2014), as modified by Goncalves-Ageitos et al. (2023), and it explicitly represents 12 individual minerals. Using multi-year global simulations, we evaluate the simulated mineralogical dust cycle with a focus on emission patterns, transport pathways, regional deposition, and the representation of seasonal and interannual variability. Model results are compared with available observations and datasets to assess the added value and limitations of mineral-resolved dust representation.The evaluation demonstrates where mineralogical information helps to better constrain dust transport and deposition and identifies key uncertainties that remain. These results provide a basis for future work on mineral-specific dust deposition and its role in biogeochemical cycles.

This paper presents an analysis of the annual cycle of aerosol optical and geometrical properties based on multiwavelength-Raman-polarization lidar measurements for Mindelo, Cabo Verde, from July 2021 to August 2023. A quality-assured data set of more than 70 automatically-calibrated lidar profiles was manually evaluated. For the first time, a two-year time series of, e.g. layer-resolved aerosol optical depth (AOD), lidar ratio profiles, and particle depolarization profiles are presented for Cabo Verde to characterize the complete annual cycle of aerosol in the planetary boundary layer (PBL) and in the lofted aerosol layers. The aerosol conditions over Mindelo are complex with different mixing states of dust and non-dust components. A strong annual cycle was found in the overall aerosol layer top height and the geometrical extent, the AOD, and the dust fraction of the lofted layers. Furthermore, the data was used to explicitly define aerosol-related seasons. The dust season (June–September) is characterized by geometrically and optically thick lofted layers dominated by Saharan dust (up to 7 km height) above a slightly polluted marine PBL. Seasonal mean lidar ratios at 355(532) nm are 34±18 (32±19) sr (PBL) and 48±19 (39±18) sr (lofted layers). The particle depolarization ratio is <0.05 (PBL) and 0.16±0.07, 0.22±0.06, and 0.20±0.05 (lofted layers) at 355, 532, and 1064 nm. The mixing season (often mixtures of Saharan dust with biomass burning aerosol, November–March) is characterized by a large variability of aerosol with mean lidar ratios of 60±32 (48±32) sr at 355 (532) nm and depolarization ratios of 0.09±0.06, 0.11±0.07, and 0.16±0.08 at 355, 532, and 1064 nm in the lofted layers.

Vegetation fires have become increasingly recognized as a potential entrainment mechanism for mineral dust. However, the global importance of this emission pathway remains largely unknown. Based on previous LES investigations, we developed a parameterization that relates the dust emission potential of wildfires to observational data of the fire radiative power and further soil‐surface conditions. It was implemented into the aerosol‐climate model ICON‐HAM and simulations with and without the new emission pathway were conducted for the 10‐year period 2004–2013. Fire‐dust emissions can account for around 230 (190–255) Tg yr ⁻¹ , which represents around 18 (15–21) % of the total global dust emissions. These additional emissions originate largely from regions that are typically not known as significant sources of mineral dust. Locally, wildfires can enhance the presence of atmospheric dust particles and on the Southern hemisphere might even surpass other forms of dust emission. Highly dust active fire regions are identified in areas where burning grasslands create suitable emission conditions together with emissive soil types despite rather weak fires, for example, in Eastern Europe or the Central US. Fire‐dust emissions are subject to a strong seasonal cycle, mainly driven by the fire activity, following the hemispheric warm and dry seasons. Multi‐year comparisons with (dust) AOD observations revealed improvements due to the additional fire‐dust emissions, particularly in the most fire‐active regions on the Southern hemisphere. Nevertheless, further research and improvements of the parameterization are required to better classify the source areas and their variation with the changing climate and land use conditions.

Mineral dust emissions from arable land are a significant environmental concern. Fugitive dust emissions commonly arise during mechanical activities such as tilling and harvesting, while aeolian emissions occur from sparsely vegetated cropland, particularly during the transitional phases between fresh tillage and substantial vegetation growth and hence coverage of the bare soil. Suspended in the atmosphere, dust aerosol particles originating from arable land suposedly affect human health, reduce air quality, and can economically impact agricultural productivity due to soil degradation and reduced yields.Agricultural dust emissions are often overlooked in coupled atmosphere-aerosol models, perhaps due to the complex conditions that lead to emissions. Fugitive emissions are highly variable, influenced by unpredictable human activities, while aeolian emissions require accurate descriptions of vegetation dynamics during transitional periods.To address these gaps, we developed modelling strategies to simulate both fugitive and aeolian emissions. Fugitive emissions were analysed using a Lagrangian particle dispersion model designed to capture the turbulent mixing of dust particles in the atmospheric boundary layer. A case study based on measured tilling emissions demonstrated how atmospheric stratification can limit or amplify dust plumes and their range of transport.For aeolian emissions, a new parameterisation was implemented in the atmosphere-aerosol model COSMO-MUSCAT, utilising high-resolution satellite data to represent vegetation cover. We tested our model for a dust emission event in Poland in 2019, where the model showed good agreement with satellite observations and ground-based measurements.Ultimately, our modelling efforts provide insights into the dynamics, spatial distribution, and broader impacts of agricultural dust emissions, contributing to a more comprehensive understanding of their role in the atmosphere.

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.

The interactions of different components of the Earth system, such as between the biosphere and the atmosphere, are still poorly understood. A major issue is understanding the consequences of increasing wildfire activity in a changing climate. Smoke particles and gases emitted from such fires affect air quality and the Earth’s radiation balance, and can potentially affect the formation of clouds and precipitation. Understanding links between biodiversity and type of vegetation, smoke emission and the atmospheric distribution and processing of these particles and gases is key for assessing potential impacts and future changes. Addressing the depth of processes in the interconnected atmosphere-climate-vegetation system requires a combination of expertise from various scientific disciplines. The new Leibniz ScienceCampus “Smoke and bioaerosols: Release, processes, and impacts in a changing climate” (BioSmoke) located in Leipzig, Germany will combine expertise in atmospheric and biodiversity research as well as atmospheric processes at several research institutions including the Leibniz Institute for Tropospheric Research and Leipzig University to study effects of the release of aerosol particles from vegetation. To this end, combustion experiments in the laboratory, field measurements of aerosol properties, and remote sensing and modelling of particle emission, transport, and atmospheric effects are envisioned. We will present an overview of the planned projects within the ScienceCampus.

Dust aerosols are a key component of the climate system due to their interactions with radiation, their influence on atmospheric chemistry, and their role in biogeochemical cycles. Despite this importance, many climate models treat mineral dust particles as a homogeneous entity, overlooking their inherent variability regarding mineralogical composition. In reality, dust aerosols consist of fine particles entrained by wind from sparsely vegetated soil surfaces, originating from geographically diverse regions of the Earth and shaped by local climate and geological conditions. These particles are a complex mixture of various mineralogies with distinct size distributions.In this study, we discuss the global distribution of mineral dust aerosol concentrations with regard to the dust particles’ mineralogical composition, using the atmosphere-aerosol model ECHAM-HAMMOZ (ECHAM6.3.0-HAM2.3-MOZ1.0). The model has been enhanced by integrating 12 minerals derived from the database of Journet et al. (2014), as modified by Gonçalves Ageitos et al. (2023). This implementation allows for a more detailed representation of the mineralogical diversity of atmospheric dust aerosols as a function of soil mineralogy at the contributing dust source areas. The results of the model simulations are evaluated against observational data in order to assess the model's accuracy and performance with regard to the representation of the mineralogical composition of dust aerosol plumes.This work highlights the importance of incorporating mineralogical diversity in climate models to better understand the role of dust aerosols in the Earth system. Gonçalves Ageitos, María & Obiso, Vincenzo & Miller, Ron & Jorba, Oriol & Klose, Martina & Dawson, Matt & Balkanski, Yves & Perlwitz, Jan & Basart, Sara & Tomaso, Enza & Escribano, Jerónimo & Macchia, Francesca & Montané Pinto, Gilbert & Mahowald, Natalie M & Green, Robert O & Thompson, David & Pérez García-Pando, Carlos. (2023). Modeling dust mineralogical composition: sensitivity to soil mineralogy atlases and their expected climate impacts. Atmospheric Chemistry and Physics. 23. 8623-8657. 10.5194/acp-23-8623-2023. Journet, E., Balkanski, Y., and Harrison, S. P.: A new data set of soil mineralogy for dust-cycle modeling, Atmos. Chem. Phys., 14, 3801–3816, https://doi.org/10.5194/acp-14-3801-2014, 2014.

Vegetation fires represent a major, mostly anthropogenically-driven, component of the Earth system that are affecting different landscapes in multiple regions of the globe and are supposed to increase further in number and severity with the ongoing climate change. Measurements and conceptional model studies have already shown that the fire-induced disturbance of the near-surface wind patterns allow for the mobilization of soil dust particles and their injection into the atmosphere through the pyro-convective updrafts related to the fires. However, the dust emission schemes of the current generation of aerosol-climate models do not consider this fire-related emission pathway and focus on wind-driven dust emissions of mostly unvegetated landscapes such as deserts only. This can result in an underrepresentation of dust particles in the fire-affected regions with consequences regarding a correct representation of aerosol-atmosphere interactions such as the radiation budget.Therefore, the present study aims to provide more insights concerning the importance of fire-driven dust emissions in the climate system. In order to achieve this, the process was implemented as a new emission pathway into the aerosol module HAM (Hamburg Aerosol Module) of the newly coupled aerosol-climate model ICON-HAM. Information about the behavior of the fire-affected wind fields and their potential to overcome typical emission thresholds have been used to set the dust emission fluxes in relation to data of the global fire activity, expressed by the fire radiative power (FRP), and to land-surface characteristics such as soil type and surface roughness.Multi-year global simulations of ICON-HAM were analyzed to quantify the impacts of the additional dust emissions caused by the fire activity and their injection parameterization on a seasonal and continental scale. It was found that the strength of the fire-related dust emissions strongly depends on the region where the fire occurs, which is determined by the local soil-surface conditions and not only by the fire strength. However, the vegetation fires can lead to an increase of the atmospheric dust load even in regions far away from those commonly known as dust source areas, highlighting that fire-driven dust emissions can substantially contribute to the total aerosol load and in particular its composition within fire-prone regions or also within a fire-prone climate.