Aerosols significantly influence Arctic cloud properties, affecting radiative balance and climate dynamics. Among them, ice-nucleating particles (INPs) are particularly impactful, as they nucleate ice at higher temperatures than homogeneous freezing, altering cloud radiative properties and lifetimes. Primary biological aerosol particles (PBAPs), a subset of aerosols of biological origin, have garnered attention due to their abundance and widespread presence. PBAPs may influence clouds more than previously recognized, particularly in the Arctic, where aerosol-cloud interactions are crucial for regional climate regulation. Understanding the sources, seasonality, and mechanisms of PBAP-induced cloud microphysics is critical, especially as Arctic environmental changes potentially amplify or mitigate these interactions.
Here, we present an overview of recent observational and experimental evidence linking PBAPs to INPs and their subsequent impact on cloud phase and radiative properties. Observations across diverse Arctic regions from Ny-Ålesund (Svalbard) to the central Arctic Ocean over the pack ice will be presented. Through a synthesis of multi-year and expedition-based studies using a wide range of experimental and modelling approaches, we provide evidence linking fluorescent PBAPs to INPs, and their yearly dominance in the high-temperature regime. Our results show that PBAPs are closely associated with heat-labile high-temperature INPs, especially during the biologically active summer and early fall seasons. Concentrations of fluorescent PBAPs range from 10-3 to 10-1 L-1, peaking in summer when biological activity and terrestrial vegetation are at their height (Freitas et al., 2023). PBAP were also for the first time directly observed in-situ within cloud residuals (dried cloud particles) using single-particle fluorescence spectroscopy and electron microscopy coupled to a ground-based counterflow virtual impactor inlet. Seasonal cloud observations linked their presence to a possible influence on the prevalence of mixed-phase clouds during warm months (Freitas et al., 2024).
While the sources of fluorescent PBAP over Svalbard are mainly suggested to be of regional and terrestrial origin, over the Arctic Ocean, marine sources emerge as significant contributors to fluorescent PBAP emissions, particularly during ice-free periods in biologically productive areas. At the North pole, air parcel trajectory analysis, combined with ocean productivity reanalysis, links episodic fluorescent PBAP and high temperature INP events to biologically active regions (Kojoj et al., 2024).
Our findings underscore the critical role of PBAPs acting as INP and in determining the phase and radiative properties of low-level Arctic MPCs. This work has important implications for improving the representation of Arctic aerosol sources - especially of biological origin - and their interactions in climate models. As the Arctic undergoes profound transformations in its hydrological and biogeochemical cycles, it is essential to understand the sources and characteristics of PBAPs and their links to INPs in order to better predict future cloud and climate dynamics in this sensitive region.
References:
Freitas et al. Nature Communications 14.1 (2023): 5997. https://doi.org/10.1038/s41467-023-41696-7
Freitas et al. Atmospheric Chemistry and Physics 24.9 (2024): 5479-5494. https://doi.org/10.5194/acp-24-5479-2024
Kojoj et al. Tellus. Series B, 76.1 (2024): 47-70. https://doi.org/10.16993/tellusb.1880
How to cite: Zieger, P., Pereira Freitas, G., and Kojoj, J. and the Arctic-Bioaerosol-INP-Team: On the abundance and sources of biological aerosol serving as ice nuclei in the high Arctic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4998, https://doi.org/10.5194/egusphere-egu25-4998, 2025.
Primary biological aerosol particles (PBAPs), including fungal spores, bacteria and pollen grains, are widely distributed in the atmosphere. Some PBAPs are highly efficient ice nucleating particles (INPs), but their impact on atmospheric ice formation is currently uncertain. PBAPs have been associated with INPs that are active at high sub-zero temperatures and may contribute disproportionally high in places with little anthropogenic influence, such as the high Arctic [1] and in the boreal forest [2].
This study investigates PBAPs and INPs in the pristine Finnish sub-Arctic at the Pallas supersite from September 2022 to September 2023. To study PBAPs, we combine measurements of highly fluorescent aerosol particles (HFAPs) with the Wideband Integrated Bioaerosol Sensor (WIBS) [3], fungal spore counts from a Hirst-type volumetric sampler and eDNA sequence analysis from filter samples. We compare PBAPs to INP measurements over a wide temperature range using the Portable Ice Nucleation Experiment (PINE) [4] and the Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology (INSEKT) [2].
We found a strong seasonal trend of a subset of HFAPs with maximum concentrations in summer and an abrupt and strong decrease with snow cover. Together with an exponential relationship with temperature, this suggests locally emitted bioaerosols. The measured bioaerosols show a positive correlation with INPs active over a wide activation temperature range (-31°C - -8°C). An exceptionally high correlation (r=0.94, p<0.001) was found for INPs active above -13.5°C, showing that WIBS is a powerful tool to predict INP concentrations in biologically dominant environments. Comparison of WIBS data with fungal spore counts indicates the fungal nature of the biological INPs. eDNA analysis revealed a much higher fungal biodiversity than the visually identified spore counts with most of the species belonging to Basidiomycota. Although we found some species known for ice nucleation (e.g. Penicillium_sp, Aspergillus_sp) the ice nucleation of most of the fungi detected has not yet been tested. Future work could contribute to the knowledge of the exact fungal species that dominate the INP population in the sub-Arctic.
This work was supported by ATMO-ACCESS under the ID ATMO-TNA-4-0000000069 and by the FFG under the Project Lab on a Drone (888109).
[1] Pereira Freitas, G. et al. (2023) Nat Commun, 14, 5997
[2] Schneider, J. et al. (2021) Atmos Chem Phys, 21, 3899- 3918
[3] Gratzl, J. et al. (2025), Earth Syst Sci Data (submitted)
[4] Möhler, O. et al. (2021). Atmos Meas Tech. 14(2), 1143-1166.
How to cite: Gratzl, J., Böhmländer, A., Möhler, O., Asmi, E., Pätsi, S., Saarto, A., Pogner, C.-E., Brus, D., Doulgeris, K. M., Stolzenburg, D., Wieland, F., and Grothe, H.: Fluorescent fungal spores as a major contributor to ice nucleating particles in the European sub-Arctic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5737, https://doi.org/10.5194/egusphere-egu25-5737, 2025.
Ice nucleating particles (INPs) are crucial for the formation and evolution of ice-containing clouds, particularly in the Arctic, where INPs are scarce. Their influence on the radiative budget and its evolution in a warming climate remains an active area of research. INP sources in the Arctic are diverse, ranging from long-range transported mineral dust to local marine biological particles. However, their representation in regional and global models remains uncertain.
In this study, we implement emissions of marine primary organic aerosols (MPOAs) and high-latitude dust in the WRF-Chem chemistry-transport model. Using a set of offline ice nucleation schemes, we evaluate the contributions of different aerosol species to INP production. Model outputs are compared with in situ INP measurements from recent Arctic campaigns, assessing the performance of nucleation schemes in terms of particle concentrations.
Modeled MPOAs appear to be a major source of INP, but only because the model strongly overestimates organic aerosols. While certain nucleation schemes successfully reproduce baseline observed INP concentrations, they fail to capture the occasional sharp drops observed in freezing temperature. By incorporating Lagrangian dispersion modelling, we demonstrate that in-cloud removal of efficient INP along the likely transport pathways of INPs may account for the observed reductions in concentrations. Building on this insight, we implement, in WRF-Chem, new INP emission schemes sensitive to online nucleation processes during atmospheric transport. These updated tracers show improved agreement with in situ INP observations, offering new perspectives for more accurate representation of Arctic INPs in models.
How to cite: Da Silva, A., Marelle, L., Lapere, R., and Raut, J.-C.: Modelling Ice Nucleating Particles from High-Latitude Sources to Reproduce Arctic In Situ Concentrations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16455, https://doi.org/10.5194/egusphere-egu25-16455, 2025.
Ice formation processes influence the radiative properties, precipitation formation and consequently cloud life time in these mixed-phase clouds. Primary ice formation is enabled by so-called ice nucleating particles (INPs). In remote marine regions such as the Southern Ocean, where INP concentrations are naturally low (McCluskey et al., 2018; Tatzelt et al., 2022), discrepancies to atmospheric observations in the representation of cloud phase with strong biases in radiative effects were identified in atmospheric models (Vergara-Temprado et al., 2018). To improve atmospheric models, a better understanding of INP sources, such as sea spray aerosol, INP properties and a physical-sound INP description are needed.
Ice nucleating macromolecules (INMs), that are produced by marine microorganisms, have been described to potentially enter the atmosphere as part of sea spray aerosol (DeMott et al., 2016; Wilson et al., 2015). While INMs produced from terrestrial micro- and more complex organisms could be attributed to e.g. specific proteins and polysaccharides (e.g., Dreischmeier et al., 2017, Frohlich-Nowoisky et al., 2015), we are lacking knowledge about the chemical identity of INMs from the marine biosphere. A polysaccharidic nature of marine INMs is likely as free glucose, a degradation product of polysaccharides and non-ice active monosaccharide, scales with ice activity of Arctic surface seawater (Zeppenfeld et al., 2019).
In this study, we present polysaccharides produced from aquatic eukaryotic microorganisms (incl. thraustochytrid, yeast, filamentous fungus) as relevant ice nucleating macromolecules (INMs) originating from the marine biosphere. In these and samples using polysaccharide standards, it could be shown that normalization by the polysaccharide mass in the sample harmonizes the freezing spectra across different microorganism and standard samples. We parameterized polysaccharidic INMs based on classical nucleation theory and applied this parameterization on global model simulations. A comparison with currently available atmospheric INP observations over the oceans demonstrates a 44% contribution of polysaccharidic INMs to the total marine INPs in the temperature range from -15 °C to -20 °C (Fig. 1). The importance of polysaccharidic INMs is highlighted for remote marine regions.
DeMott, P.J., et al. (2016). Proceedings of the National Academy of Sciences 113, 5797-5803.
Dreischmeier, K., et al. (2017). Scientific Reports 7.
Frohlich-Nowoisky, J., et al. (2015). Biogeosciences 12, 1057-1071.
McCluskey, C.S., et al. (2018). Geophysical Research Letters 45, 11989-11997.
Tatzelt, C., et al. (2022). Atmospheric Chemistry and Physics 22, 9721-9745.
Vergara-Temprado, J., et al. (2018). Proceedings of the National Academy of Sciences 115, 2687-2692.
Wilson, T.W., et al. (2015). Nature 525, 234-+.
Zeppenfeld, S., et al. (2019). Environmental Science & Technology 53, 8747-8756.
How to cite: Schrödner, R., Hartmann, S., Hassett, B., Hartmann, M., van Pinxteren, M., Fomba, K. W., Stratmann, F., Herrmann, H., Pöhlker, M., and Zeppenfeld, S.: Polysaccharides - Important Constituents of Ice Nucleating Particles of Marine Origin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15357, https://doi.org/10.5194/egusphere-egu25-15357, 2025.
Alkali feldspar undergoes a variety of phase transformations during cooling from magmatic crystallization leading to increasing ordering of Al and Si on the tetrahedrally coordinated lattice sites and to grain-internal microstructures such as twins and exsolution lamellae and associated surface topography. Both, Al-Si ordering as well as the specific surface topography may contribute to the extraordinary ice nucleation activity of alkali feldspar. We studied seven natural alkali feldspars ranging from homogeneous and featureless gem-quality sanidine with disordered Al-Si to hydrothermally altered microcline with ordered Al-Si, several generations of exsolution lamellae and micropore-rich regions associated with domains of hydrothermal albitization. (010) and (001) cleavage plates were produced from each feldspar sample and mounted in a cooling stage. Then an array of 7nl droplets of ultra-pure water was applied and cooled at 2 K/min. Droplet freezing events were recorded with an infrared camera.
The highest freezing temperatures are observed on (010) cleavage plates of K-rich (XK=0.94) microcline that exhibits 1-8 µm wide albite exsolution lamellae and 20-100 µm wide microporous regions along cracks related to hydrothermal albitization. In contrast, featureless (001) plates of gem-quality sanidines show freezing at over 10 K lower temperatures. The enhanced ice nucleation activity is tentatively ascribed to Si-Al ordering [1] and to heterogeneous ice nucleation on the surface features related to the grain-internal microstructures [2]. Which one of the two factors is more important is still unresolved.
[1] Franceschi G., Conti A., Lezuo L., Abart R., Mittendorfer F., Schmid M., Diebold U. (2023) How Water Binds to Microcline Feldspar (001), J. Phys. Chem. Lett., Vol. 15, 1, 15–22, https://doi.org/10.1021/acs.jpclett.3c03235
[2] Kiselev, A., Keinert, A., Gaedeke, T., Leisner, T., Sutter, C., Petrishcheva, E., Abart, R. (2021) Effect of chemically induced fracturing on the ice nucleation activity of alkali feldspar. Atmospheric Chemistry and Physics, 21 (15): 11801-11814, DOI 10.5194/acp-21-11801-2021
How to cite: Heuser, D. A., Hagn, M., Seidel, J., Petrishcheva, E., Abart, R., and Kiselev, A.: Surface topography and ice nucleation activity of alkali feldspar, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3750, https://doi.org/10.5194/egusphere-egu25-3750, 2025.
Ice nucleating particles (INP) play a crucial role in shaping Earth's weather and climate by influencing cloud properties and precipitation behavior. However, their abundance in the free troposphere and transport mechanisms remain poorly characterized. INP sources are generally at ground level and large-scale atmospheric vertical motion, which could lift INP from the ground into the free troposphere is often accompanied by cloud formation. The fate of INP in clouds, whether they are lifted up or washed out, is still mostly unclear.
During the HALO aircraft campaign CIRRUS-HL in June and July 2021, aerosol particles and cloud particle residuals were collected on filters using the airborne High-volume flow aERosol particle filter sAmpler (HERA). Offline laboratory analysis of these filters yield immersion mode INP concentrations. Here we present a case study with which we investigate the vertical transport and cloud processing of INP in deep convective clouds (DCC) by analyzing residuals in clouds and aerosol particles in cloud-free inflow and outflow of DCC.
Our results show that INP active above -15°C are diminished in anvil cirrus cloud particle residuals, while INP active below -20°C are found in high concentrations in DCC outflow air. We propose that precipitation formation wash out INP active at high temperatures, while INP active at low temperatures are efficiently transport upwards into the upper troposphere with ambient temperatures below -40°C, i.e., far below the INP immersion freezing temperature. With that, DCC outflow INP concentration are at least two order of magnitude above typical upper tropospheric/lower stratospheric INP concentrations derived throughout the CIRRUS-HL campaign.
This study provides new insights into the vertical transport and cloud processing of INP in the free troposphere with implications for balance between heterogeneous and homogeneous freezing in cirrus clouds.
How to cite: Schaefer, J., Grawe, S., Clemen, H.-C., Schneider, J., Wetzel, B., Mertes, S., Sauer, D., Wolf, J., Mayer, J., Tomsche, L., Schrödner, R., Henning, S., Jurkat-Witschas, T., Voigt, C., Ziereis, H., Harlaß, T., Pöhlker, M., and Stratmann, F.: Vertical transport and segregation of ice nucleating particles in deep convective clouds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20340, https://doi.org/10.5194/egusphere-egu25-20340, 2025.
The most important milestone in a mixed-phase cloud’s life is the initiation of ice. If we cannot sufficiently capture this process in weather and climate models then it is unlikely that the cloud’s properties and evolution will be accurately represented. Here we focus on improving the representation of ice-nucleating particles (INPs), which are the fundamental link between aerosols and primary ice production in mixed-phase clouds.
We use a newly collated dataset of 20 campaigns from across the northern hemisphere using Portable Ice Nucleation Experiment (PINE) instruments together with nudged simulations of the UK Earth System Model, which includes a modal aerosol microphysics model. We use 30,000 collocated PINE measurements and output from the UK Earth System Model to derive a new parameterization that links the full dust size distribution to an INP concentration. We base the functional shape of the parameterization assuming the presence of a mineral component and a biogenic ice-nucleating component, which is consistent with recent understanding.
The new parameterization reproduces 80% of the 30,000 PINE measurements within a factor of 2 and 96% within a factor of 10, and UKESM simulations correctly represent many of the short term synoptic events seen in the PINE time series. The new parameterization also performs considerably better than alternative parameterizations. The analysis shows that the INP concentrations are correlated with the dust surface area but cannot be explained by the mineral component (K-feldspar) alone. The new parameterization is consistent with the spread of laboratory derived activity for mineral soils that contain biogenic material, suggesting a biogenic ice-nucleating component associated with dust is prevalent throughout the northern hemisphere.
How to cite: Murray, B., Herbert, R., Ken, C., Mark, T., Martin, D., Ottamr, M., Larissa, L., Alex, B., Nicole, B., Naruki, H., Aiden, P., Evelyn, F., Céline, P., Antoine, C., and Ping, T.: A new parameterization for simulating global ice-nucleating particle concentrations based on long-term measurements with a network of expansion chambers , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20540, https://doi.org/10.5194/egusphere-egu25-20540, 2025.
As part of the CERTAINTY project, we present results from our laboratory study of secondary ice production (SIP) from collisions between supercooled raindrops and more massive ice particles, building on our previous proof-of-concept work (James et al., 2021) with a refined experimental setup for improved quantification.
In mixed phase clouds, ice formation can occur via two pathways: primary ice formation, via ice nucleating particles, or secondary ice production (SIP). Observations in both shallow and deep convective clouds often show ice concentrations that exceed those predicted by primary ice nucleation by several orders of magnitude. However, parameterisations of SIP mechanisms remain poorly constrained due to limited laboratory data.
One proposed SIP mechanism involves collisions between supercooled raindrops and more massive ice particles, where secondary drops may form during impact, with some freezing to create secondary ice. Our previous work (James et al., 2021) demonstrated the viability of this SIP mechanism, and showed that approximately 30 % of the secondary drops froze under a limited set of conditions. Building on this, we have refined our experimental setup to reduce uncertainties in the freezing fraction of secondary drops by elevating the ice particle to allow the splashing to occur freely, without interference of a flat surface used in our previous experiments. We also explore a broader range of supercooled water drop diameters, ice particle sizes, impact velocities and temperatures to better reflect cloud conditions.
Finally, we incorporate our updated results into a parcel model with bin microphysics for idealised clouds, which previously used our earlier results (James et al. 2023), to demonstrate the impact this improved quantification in conjunction with other SIP mechanisms.
References
James, R. L., Phillips, V. T. J., and Connolly, P. J. (2021), Secondary ice production during the break-up of freezing water drops on impact with ice particles, Atmos. Chem. Phys., 21, 18519–18530, https://doi.org/10.5194/acp-21-18519-2021.
James, R. L., Crosier, J., and Connolly, P. J. (2023), A bin microphysics parcel model investigation of secondary ice formation in an idealised shallow convective cloud, Atmos. Chem. Phys., 23, 9099–9121, https://doi.org/10.5194/acp-23-9099-2023.
How to cite: James, R., Crosier, J., and Connnolly, P.: A laboratory study of secondary ice production from collisions between supercooled raindrops and ice particles, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6371, https://doi.org/10.5194/egusphere-egu25-6371, 2025.
The phase of low-level clouds plays a crucial role in their interaction with radiation, particularly in the Arctic. Despite the Arctic's notably clean air, characterized by low aerosol and ice nucleating particle (INP) concentrations, cloud ice can still be observed at relatively warm sub-zero temperatures.
We present a modeling closure analysis of an Arctic low-level mixed-phase cloud observed during the 2023 ARTofMELT (Atmospheric rivers and the onset of sea ice melt) campaign using the large eddy simulation model MIMICA. Comprehensive measurements of INPs and aerosols were taken at the surface, within, and above the cloud. By combining modeling and observations, we will explore which aerosol population was necessary to aid in the formation of ice within the cloud.
The minimum observed in-cloud temperature was -8 °C, with ice present throughout the cloud’s lifetime. The highest temperature at which INPs were detected was -13 °C, with an INP concentration of approximately 1.6e-4 /L. Our findings indicate that observed INP concentrations alone are insufficient to produce a significant amount of ice in the model. This suggests the need for other processes like secondary ice formation and INP recycling, or a possible misrepresentation of microphysical processes in the model. By utilizing the model and including these missing processes, we aim to determine the necessary INP concentrations and properties, as well as the secondary ice mechanisms, to account for the observed ice. This includes analyzing the importance of local versus long-range transported aerosols and primary versus secondary ice production.
How to cite: Frostenberg, H., Creamean, J., Mavis, C., Santos, L., Thomson, E. S., Ekman, A. M. L., and Ickes, L.: Which INPs and secondary ice processes are necessary to accurately model a warm Arctic mixed-phase cloud? , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-898, https://doi.org/10.5194/egusphere-egu25-898, 2025.
Secondary Ice Production (SIP) has been ascribed to the formation of new ice particles from preexisting ones. Fragmentation of ice particles during collision is one among the known SIP processes. Some of the studies have used theoretical formulation of this SIP processes in the cloud micro-physics scheme of numerical atmospheric models. However, there has been a lack of observational data for better understanding of the SIP process. This study reports fragmentation of naturally falling snow during their collision with graupel/hail particles based on the observation at Jungfraujoch, a mountain pass in the Alps located about 3.4 km above mean sea level. The study used a specially designed portable chamber to observe the fragmentation of snow particles outdoor. Based on the observational study, we optimised the theoretical formulation for the prediction of number of fragments arising from the collision between non-dendritic snow and hail/graupel. The observations show an average number of fragments per collision of about 5. The study improved the prediction of SIP through fragmentation compared to our original theoretical formulation, for snow in the non-dendritic regime of temperatures less than -170C.
How to cite: Paul, F., Gautam, M., Waman, D., Patade, S., Dutta, U., Pichler, C., Jackowicz-Korczynski, M., and Phillips, V.: Improved Formulation of Snow Fragmentation during Collision with Hail/ Graupel based on Field Observation at Jungfraujoch, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2169, https://doi.org/10.5194/egusphere-egu25-2169, 2025.
Ice-nucleating particles (INPs) can modulate the cloud-phase feedback, where the albedo of mixed-phase clouds increases in a warming climate. Mid-to-high latitude shallow cloud systems such as cold-air outbreaks (CAOs) are particularly important for cloud-phase feedbacks and sensitive to INPs. While previous studies have looked at the impact of INP concentration on CAOs, few studies have considered the life cycle of INPs in cold-air outbreaks, and the consequences for cloud albedo.
To understand how INPs are processed in CAOs, we are performing regional modelling of a CAO observed over the Norwegian Sea during the 2022 Arctic Cold Air Outbreak field campaign. Airborne INP measurements during this CAO revealed a reduction in INP concentration as the CAO developed despite the addition of sea-spray aerosol downstream in the outbreak (Raif, et al. 2024). We will test the hypothesis that INPs in air flowing into Arctic CAOs initially overwhelms local surface sources of aerosol, but are removed through precipitation processes as air moves south.
To do this, we are using the UK Met Office Unified Model with a new two-moment microphysics scheme utilising two-way interaction between cloud and aerosol tracers. Using in-situ measurements of aerosol and INPs, we will test the sensitivity of CAO development to the entrainment of INPs, removal of INPs through precipitation and redistribution of INPs after sublimation/evaporation.
Reference: Raif, et al. (2024). High ice-nucleating particle concentrations associated with Arctic haze in springtime cold-air outbreaks, Atmos. Chem. Phys. https://doi.org/10.5194/acp-24-14045-2024
How to cite: Raif, E., Field, P., Murray, B., and Carslaw, K.: Life cycle of ice-nucleating particles in an Arctic cold air outbreak, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2825, https://doi.org/10.5194/egusphere-egu25-2825, 2025.
One of the major causes for uncertainties in atmospheric modelling are aerosol-cloud-interactions as stated in the IPCC report WG1 in 2021. The aerosols available in the atmosphere can act as cloud condensation nuclei (CCNs) or ice nucleating particles (INPs) and thereby have a direct effect on cloud formation and properties. The investigation of those effects is not easy since these properties also depend on other atmospheric conditions such as the synoptic state. In volcanic eruptions the emitted aerosols are a local perturbation in the atmospheric aerosol distribution independent of synoptic conditions. The volcanic aerosols such as SO2 reacting to sulfuric acid or volcanic ash can act as CCNs and INPs respectively. Simulations with and without the eruption can be compared to directly quantify the effect of the volcanic aerosols on cloud properties. The simulations with an eruption can be compared to obervational data to verify the simulation results and improve the simulation setup.
In the presented work, the eruption of the Raikoke volcano in 2019 has been simulated using the ICOsahedral Nonhydrostatic model (ICON) and the module for Aerosols and Reactive Trace gases (ART) in limited area mode with up to 2.5 km horizontal resolution. The simulated area contains both the location of the eruption and a large cloud system consisting of liquid, mixed-phase and ice clouds. The eruption is modelled using the module fplume, a dynamics driven model predicting the vertical distribution of the emitted aerosols at the source. An ice nucleation parameterization specific for volcanic ash derived in laboratory experiments by Umo et al. (2021) for heterogeneous freezing has been implemented in the model.
First preliminary results will be shown with a focus on cloud hydrometeor properties of mixed-phase and ice clouds. Due to the location of the volcanic plume above the low liquid clouds it is found that ice crystal properties are more affected than liquid hydrometeors. The results using the ice nucleation parameterization by Umo et al. are compared to the commonly used parameterization for mineral dust particles by Ullrich et al. (2017). By specifically enabling aerosol-radiation and aerosol-cloud interactions seperately the direct and indirect impact of the eruption on the radiation balance will be quantified.
How to cite: Sebisch, M., Zarei, F., Bruckert, J., and Hoose, C.: How do volcanic eruptions effect cloud hydrometeor properties?A case study of the Raikoke eruption 2019, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4346, https://doi.org/10.5194/egusphere-egu25-4346, 2025.
In the Southwest of Germany and the North of Switzerland, there is a wind known as Bise, roughly blowing from Northeast. Associated with this wind, an extensive and long-living stratiform cloud deck can form in the winter months.
For this study, measurements were done at two different locations, both protruding above the surrounding landscape: Hohenpeißenberg (47.801°N,11.009°E, elevation 950m, station of the German Weather Service DWD, ~ 50km southwest of Munich) and Eriswil (47.071°N,7.873°E, elevation 920m, ~ 60 km southwest of Zurich). During a Bise situation, there is typically a stratus cloud at and between both locations, with winds blowing roughly from Hohenpeißenberg to Eriswil. During two Bise periods in January and February 2024, we collected aerosol particles onto polycarbonate filters at both sites. Sampling was conducted with a Digitel low-volume sampler. Sampling time was 12 hours for each filter, with a flow rate of 25 l/min. Collected filters were examined for their INP (Ice Nucleating Particle) concentrations with well-established offline methods at TROPOS.
When the Bise cloud was present at both Hohenpeißenberg and Eriswil, INP spectra at both locations were very similar. In January (Bise-1), temperatures in the boundary layer were below 0°C, and INP spectra did not show a high fraction of INPs with biogenic origin. In February (Bise-2), temperatures in the boundary layer had already risen to be constantly above 0°C. Much higher INP concentrations were observed for the whole INP spectra during Bise-2. This increase was particularly strong for freezing temperatures above -12°C, caused by additional heat labile INPs of biogenic origin. The difference in INP concentrations between the two Bise situations may at least partially originate in INP removal through ice nucleation with subsequent precipitation formation during Bise-1 which did not occur during Bise-2.
During Bise-1, there was a phase when at Hohenpeißenberg the inversion decreased in altitude by a few hundred meters. With this, the measurement site protruded above the Bise cloud, while at the same time the temperature at the ground in Hohenpeißenberg increased from -10°C to just below 0°C. Meanwhile, the Bise cloud was still present at Eriswil. While INP spectra had been similar at Hohenpeißenberg and Eriswil when both sites were in the Bise cloud, during this phase of more than a day, INP spectra at Hohenpeißenberg showed much higher concentrations and additional heat labile INPs. The changed conditions reflect the situation in the free troposphere, and we suggest the free troposphere as a source for INPs for the Bise clouds.
How to cite: Wex, H., Ohneiser, K., Hartmann, M., Hardt, A., Miller, A. J., Kanji, Z. A., Henneberger, J., Baudrexl, K., and Seifert, P.: Comparing ice-nucleating particles in extensive stratiform clouds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4383, https://doi.org/10.5194/egusphere-egu25-4383, 2025.
Biomass burning aerosols (BBA) significantly contribute to the global aerosol burden, thereby influencing air quality and global climate. The chemical properties and ice nucleation activity of BBA remain poorly constrained due to the heterogeneity of biomass sources and the complexity of atmospheric aging processes. This study comprehensively investigates the chemical composition and ice nucleation of BBA generated from laboratory-controlled burns using various biomass types and burning conditions. Both freshly emitted and photochemically aged BBA exhibit distinct and reproducible chemical compositions. However, the ice nucleation activity of BBA shows substantial variability at mixed-phase cloud temperatures and cannot be predicted by the chemical variability of the organic and inroganic carbon content. This indicates that the carbonaceous components of BBA are not a predictor for ice nucleation activity of BBA. Using laboratory data, we further evaluate the impact of BBA on atmospheric ice nucleation based on particulate matter mass concentration and equivalent spherical diameter. The estimated ice nucleating particle concentrations from laboratory-produced BBA are lower than those observed during BBA pollution in field studies. We hypothesize that the discrepancy likely arises from the co-lofting of mineral particles during real-world biomass burning events, such as ash or soil particles. These particles, which are absent in our experiments but abundant in field observations, may be an important source of atmospheric INPs, rather than carbonaceous-rich particles from combustion. The role of mineral particles in the INP concentrations of BBA is not quantified in this study, further research to address co-lofting of mineral particles with BBA is encouraged.
How to cite: Chen, J., Martin Othmar Jakob, F., Voliotis, A., Wu, H., Aisyah Syafira, S., Oghama, O., Shardt, N., Fauré, N., Kong, X., Mcfiggans, G., and A. Kanji, Z.: Ice Nucleation Abilities and Chemical Characteristics of Laboratory-Generated and Aged Biomass Burning Aerosol, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6935, https://doi.org/10.5194/egusphere-egu25-6935, 2025.
Oceans cover more than 70% of the Earth’s surface and are a critical component of global climate system. Sea spray aerosols (SSAs), derived from ocean surfaces, represent a unique and significant source of ice nucleating particles (INPs) and cloud condensation nuclei (CCN), yet their contribution to cloud processes remains poorly understood, with substantial uncertainties surrounding their role in climate systems. To address this gap, we investigate the atmospheric photochemical effects on marine aerosols and their implications for ice nucleation and droplet activation through controlled laboratory experiments.
Our study utilizes two key experimental systems: the AIDAd (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber and PINE (Portable Ice Nucleation Experiment). AIDAd, with its temperature-controlled walls capable of simulating temperature range from +30 °C to −55 °C and tropospheric cooling rates up to 10 °C min⁻¹, allows for precise investigations of aerosol-cloud interactions. PINE measures INP concentrations under mixed-phase cloud conditions at temperatures ranging from −10 °C to −38 °C.
For our experiments, marine aerosols were generated from three distinct seawater samples collected from diverse oceanic regions: the Indian Ocean, the South China Sea, and Jangmok Port (Korea). These samples capture the variability of natural marine environments and provide a comprehensive basis for understanding the effects of geographical and biological diversity on aerosol properties. These samples underwent photochemical treatment using a custom-built solar radiation simulator to replicate atmospheric conditions. The irradiated aerosols are subsequently analyzed using the AIDAd chamber and PINE, and further chemical analysis are done to evaluate changes in composition and ice nucleation potential.
This study provides critical insights into the interplay between marine aerosol sources, photochemistry, and cloud formation. By integrating data from AIDAd and PINE, we aim to unravel the mechanisms underlying ice nucleation and droplet activation of marine aerosols under simulated atmospheric conditions. Our findings will contribute to reducing uncertainties in the representation of marine aerosol-cloud interactions in climate models, enhancing our understanding of their role in the Earth's climate system.
How to cite: Kim, N., Abdelmonem, A., Umo, N. S., Wagner, R., Lacher, L., Möhler, O., Li, H., Saathoff, H., Kim, K. H., Park, D.-H., Ahn, C., Kim, D. H., Yim, U. H., Yum, S. S., and Choi, S.: The Impact of Atmospheric Photochemistry on Marine Aerosols: Ice Nucleation and Droplet Activation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8753, https://doi.org/10.5194/egusphere-egu25-8753, 2025.
The challenges of global warming and climate change demand climate models with accurate projections to effectively plan adaptation and mitigation strategies. However, significant uncertainties persist in current climate models. One key uncertainty involves the behavior of mixed-phase clouds, which consist of supercooled droplets and ice crystals. The dynamics between the phases within these clouds are critical to understanding precipitation and cloud albedo, both of which influence the regulation of global warming [1].
Aerosol particles capable of nucleating ice, known as ice-nucleating particles (INPs), play a vital role in these mixed-phase dynamics. Numerous studies have examined how materials' surface properties modify water structure at the interface, modifying their ice nucleation activity [2]. Among the various INPs present in the atmosphere, feldspars have garnered substantial attention over the past decade due to their high nucleation efficiency. This efficiency has been shown to be affected by felspar surface properties such as surface chemistry, structure or morphology [3]
In this presentation, we will share our analysis of feldspar samples collected from various mines in Europe and Africa, focusing on the evolution of their ice-nucleation efficiency after prolonged immersion in water. Using droplet-freezing assay experiments, we identified different categories of ice-nucleation sites, utilizing an analytical method developed by our team [4]. We investigated the evolution of these site families over time in water, finding that some sites disappeared while others remained stable.X-ray diffraction studies show that the feldspar samples used in the previous tests undergo weathering and evolve to stable mineral and/or amphipathic phases under new conditions. Our results demonstrate that feldspar particles within clouds can undergo transformations when immersed in water droplets, altering their ice-nucleation efficiency over timescales of just a few weeks.
[1]“Ice-Nucleating Particles That Impact Clouds and Climate: Observational and Modeling Research Needs” S. M. Burrows et al. Rev. Geophys. 60 (2) e2021RG000745 (2022)
[2]” Water at surfaces and interfaces: From molecules to ice and bulk liquid.” T.K. Shimizu, S. Mayer, A. Verdaguer, J.J. Velasco-Velez, M. Salmeron. Progress in Surface Science 4, 87(2018).
[3]“Pores Dominate Ice Nucleation on Feldspars” E. Pach and A. Verdaguer J. Phys. Chem. C 123, 34, 20998–21004, (2019)
[4] “HUB: A method to model and extract the distribution of ice nucleation temperatures from drop-freezing experiments” I. de Almeida Ribeiro, K. Meister, V. Molinero, Atmospheric Chemistry and Physics, 23 (10), 5623-5639, (2023)
How to cite: Verdaguer, A., Canet, J., Rodríguez, L., Garcia-Valles, M., Renzer, G., Bonn, M., and Meister, K.: Aging of feldspar ice nucleation particles immersed in water: the loss of ice-nucleation efficiency of mineral particles in clouds., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9444, https://doi.org/10.5194/egusphere-egu25-9444, 2025.
A minor and strongly temperature-dependent fraction of atmospheric aerosols, called Ice Nucleating Particles (INPs), is known to impact the weather and climate systems by inducing the formation of ice in mixed-phase and cirrus clouds. There is increasing evidence that INPs not only induce the formation of precipitation in particular over continental areas, but also have an important impact on the radiative properties of a number of cloud types throughout the troposphere. For cirrus formation, the abundance and types of INPs play important roles in the interplay between heterogeneous and homogeneous ice nucleation pathways, leading to either net cooling or heating of cirrus clouds in the global climate system.
During the previous years, the new instrument PINEair was developed for measuring INPs at cirrus formation temperatures between -40°C and -65°C and ice supersaturations of up to about 100%. The new instrument can be operated both onboard research aircrafts or at high altitude mountain stations. It is based on the PINE (Portable Ice Nucleation Experiment) instrument, which was developed for laboratory experiments on ice nucleation processes and for automated operation during longer-term INP monitoring activities in the field. PINEair is developed and optimized for direct sampling in the free troposphere.
This contribution will explain the working principle of the new instrument, describe the development and setup of the prototype version, discuss the results of first INP measurements both in the laboratory and at a high-altitude mountain station, and outlines the next steps for building the final aircraft-based version of PINEair.
How to cite: Möhler, O., Bogert, P., Böhmländer, A., Büttner, N., Curtius, J., Lacher, L., Schrod, J., and Ullrich, R.: A new instrument for measuring ice-nucleating particles in the free troposphere and at temperatures relevant for cirrus formation: development and first applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13737, https://doi.org/10.5194/egusphere-egu25-13737, 2025.
Ice formation in clouds occurs over a wide temperature range (-5°C to -40°C) during primary and secondary ice formation. In most clouds, primary ice formation (PIP) is generated by ice-forming aerosol particles (INP) through heterogeneous nucleation. Observations show that the concentration of ice crystals often exceeds the concentration of available active ice nuclei. This suggests that ice crystals can be generated by secondary processes (SIP). In contrast to PIP, the range of possible processes for SIP is not yet fully understood.
The aim of this study is to identify what are the dominant SIP mechanisms at different environmental conditions, such as temperature, liquid water content, primary ice formation and different CCN and INP concentrations.
At the current state of the research we have performed numerical experiments to study the impact of the different ice splintering mechanisms (due the freezing of the water drops; ice – ice collision and Hallett-Mossop process) at different environmental conditions. A detailed microphysics scheme (University of Pécs-NCAR Bin scheme) implemented in a 2D kinematic framework were used to perform the numerical experiments.
How to cite: Sarkadi, N. and Geresdi, I.: Sensitivity studies on secondary ice processes using detailed microphysics scheme, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16405, https://doi.org/10.5194/egusphere-egu25-16405, 2025.
Secondary ice production (SIP) is believed to be responsible for the majority of ice particles observed in precipitating clouds with temperatures above −36°C, based on various field observations from both aircraft and ground-based studies worldwide. One known mechanism of SIP is the fragmentation of ice particles during collisions. This process has been explored using a theoretical model, which has been incorporated into the microphysical schemes of some atmospheric models, where it has been shown to significantly influence cloud glaciation and radiative properties. However, there has been a lack of experimental field studies, particularly those involving naturally falling snowflakes, to better understand this specific SIP mechanism. This study presents the first field measurements of fragmentation during collisions between naturally falling snowflakes and graupel/hail particles, using a newly designed portable chamber deployed outdoors in northern Sweden. Based on these field observations, we refined the existing model for predicting the number of fragments produced by collisions between snow and graupel/hail. The data revealed that, on average, dendritic snowflakes (3–12 mm) produced about 12 fragments per collision, while nondendritic snowflakes (1–3 mm) produced around 1 fragment. This represents an increase in predicted fragment numbers compared to our original model published in 2017. The updated fragmentation model for ice–ice collisions can now be integrated into atmospheric models’ microphysical schemes.
How to cite: Gautam, M., Waman, D., Patade, S., Deshmukh, A., Paul, F., Smith, P., Bansemer, A., Jackowicz-Korczynski, M., and Phillips, V.: Fragmentation in Collisions of Snow with Graupel/Hail: New Formulation fromField Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16421, https://doi.org/10.5194/egusphere-egu25-16421, 2025.
Mineral dust is one of the most abundant types of aerosol particles in the atmosphere, playing a crucial role in various atmospheric processes. A key interaction within clouds is its ability to produce ice-nucleating particles (INPs), influencing cloud properties such as phase, lifetime, and water content. The efficiency of mineral dust as INPs depends on factors such as mineralogy, composition, and particle size. This study investigates the role of particle size and mineralogy in INP efficiency, contrasting Morocco and Iceland, i.e. a mid- and a high-latitude dust sources by using developed parameterizations in ICON-ART.
For this purpose, we used experimental results obtained with the AIDA chamber and the INSEKT freezing assay. The experiments tested ice production in immersion freezing mode for samples from Morocco and Iceland with different size distributions including large particles (greater than 10 µm in diameter). Our analysis revealed notable differences in INP efficiency for the two source locations. The ice nucleation active surface site (INAS) density indicated no significant size dependence for Moroccan samples. In contrast, Icelandic samples exhibited a subtle size dependence, with larger particles showing slightly reduced activity. This behavior was linked to the dust mineralogical composition, specifically the presence of pyroxene. For Icelandic samples, the pyroxene relative volume fraction decreases with increasing particle size, which correlates with the observed reduction in INP activity.
Based on these insights, we developed a new INAS density parameterization for Icelandic dust and proposed a modification to the equation used to compute INAS density to represent the variation in the efficiency of ice nucleation activity at different diameters. We then used this new parameterization in the ICON-ART model to test the impact of a different ice nucleation efficiency of Icelandic dust on a regional scale. By using ICON-ART global dust distributions were simulated and surface dust was used as input for the new parameterizations at different temperatures, recreating typical field experiments on ice nucleation.
This study underscores the importance of characterizing both mineralogical composition and its size dependence when developing parameterizations for INP activity. Our results challenge the assumption that larger particles are always more efficient INPs in immersion freezing mode, as their efficiency is linked not only to their large surface areas but also to their mineralogical composition, which can vary for different sizes. Additionally, size distribution shapes should be considered as another factor influencing INP concentration as the abundance of particles at different diameters might determine the efficiency of the sample.
How to cite: Vergara Palacio, S., Panta, A., Baer, A., González-Romero, A., Querol, X., Kandler, K., Pérez García-Pando, C., Hoose, C., and Klose, M.: Dependence of ice nucleation activity on mineralogy and particle size of surface dust from Morocco and Iceland in immersion freezing mode., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16438, https://doi.org/10.5194/egusphere-egu25-16438, 2025.
Mixed-phase clouds play a key role in weather and climate and are a major challenge to model accurately in models. Nevertheless, considerable progress on modeling microphysical processes in mixed-phase clouds, such as primary and Secondary Ice Production (SIP) has led to systematic improvements in model performance.
Here, we use the Weather Research and Forecasting (WRF) model with the EPFL/FORTH cloud microphysical scheme improvements (Georgakaki et al., 2024) to simulate weather, cloud formation and precipitation events sampled during the Cleancloud Helmos OrograPhic sIte experimeNt (CHOPIN) campaign during the Fall of 2024 to Spring of 2025. CHOPIN takes place at Mount Helmos in the Peloponnese, Greece, an ideal location for studying aerosol-cloud interactions in orographic mixed-phase clouds.
The performance of SIP parameterizations in WRF are evaluated by (i) comparing model outputs to meteorological data from both a fixed weather station and radiosondes, (ii) comparing the model's ability to capture boundary layer dynamics using atmospheric trace gasses as a proxy, and (iii) the model's ability to capture cloud formation using reflectivity from a Ka-band (35 GHz) radar, by comparing the output of a forward operator (radar simulation) from the modeled cloud fields. Through the modelling of various days between October 2024 and December 2024, as well as a clustering analysis of the radar reflectivities, the capabilities of using SIP parameterizations in WRF are assessed with respect to particular cloud regimes. We see that distinct improvements are seen in the simulated fields, particularly for the clusters associated with cloud fields that are developed and regional in nature.
How to cite: Waseem, A., Georgakaki, P., Clerx, N., Foskinis, R., Molina, C., Gini, M., Billault-Roux, A.-C., Zieger, P., Eleftheriadis, K., Berne, A., and Nenes, A.: An Investigation of the Validity of Secondary Ice Production Parameterizations in WRF in an Orographic Environment with Preliminary Data From CHOPIN, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18611, https://doi.org/10.5194/egusphere-egu25-18611, 2025.
Posters virtual: Wed, 30 Apr, 14:00–15:45 | vPoster spot 5
EGU25-3841 | ECS | Posters virtual | VPS3
SeParation of Ice Nuclei via Density Layers (SPINDL): A new method for characterizing ice nuclei using density gradient centrifugationWed, 30 Apr, 14:00–15:45 (CEST) vPoster spot 5 | vP5.1
Atmospheric ice nucleating substances (INSs) play a crucial role in ice cloud formation above -35°C, impacting cloud radiative properties, cloud lifetime, and the hydrological cycle. Characterizing inorganic (e.g., mineral dusts, volcanic ash, metals) and organic (e.g., bacterial cells, fungal spores, pollen, and various biomacromolecules) INSs has typically involved: 1) single-particle analyses, which offer high resolution but require specialized equipment, and 2) bulk sample treatment (e.g., heat, H2O2, (NH₄)₂SO₄) analyses, which are more accessible but may overestimate or underestimate INS concentrations due to non-target effects. There is a need for additional methods to quantify inorganic and organic INSs concentrations in the atmosphere to test and improve climate models.
Here we show a new density gradient centrifugation method to differentiate and quantify inorganic (densities ≥ 2.1 g cm-3) and organic INSs (densities ≤ 1.6 g cm-3). Density gradient centrifugation was used to separate the INSs suspension into their respective density isolate. This was followed by a wash procedure consisting of sequential differential centrifugation and ultrafiltration. Lastly, the INSs were quantified using a droplet freezing assay.
Our method successfully recovered organic water-soluble INSs (lignin, birch pollen washing water and filtered Fusarium acuminatum) and organic water-insoluble INSs (Snomax and Pseudomonas syringae) in the low-density isolate. We recovered inorganic water-insoluble INSs (K-feldspar) in the high-density isolate. In an INS mixed suspension, we recovered K-feldspar in the high-density isolate and lignin in the low-density isolate both at concentrations similar to the isolated K-feldspar or lignin tests.
This work demonstrates the broad applicability of density gradient centrifugation for characterizing a wide range of inorganic and organic atmospheric INSs.
How to cite: Uppal, G. K., Worthy, S. E., Chen, L., Yeung, C., McConville, O., and Bertram, A. K.: SeParation of Ice Nuclei via Density Layers (SPINDL): A new method for characterizing ice nuclei using density gradient centrifugation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3841, https://doi.org/10.5194/egusphere-egu25-3841, 2025.
