Physical and Chemical Properties of Cloud Droplet Residuals and Aerosol Particles During the Arctic Ocean 2018 Expedition

Abstract

The Arctic is warming faster than any other environment on the planet (Manabe & Wetherald, 1975;Serreze & Barry, 2011). The accelerated warming-Arctic amplification-leads to other changes, such as sea ice decline, glacier melt, permafrost thaw, and changes in the composition of the biological communities in the Arctic Ocean (e.g., AMAP, 2015). Aerosol particles can affect Arctic climate directly, through interactions with radiation (e.g., AMAP, 2015), and indirectly, through interactions with clouds (Albrecht, 1989;Mauritsen et al., 2011;Twomey, 1977). Our limited understanding of the feedback mechanisms and local processes related to clouds and aerosol-cloud interactions in the Arctic contributes significantly to the uncertainty in projections of future Arctic climate (IPCC, 2013). The large differences between polar night and day in terms of, for example, radiation, sea ice, cloud type and phase (liquid, mixed-phase, or ice), and atmospheric circulation result in large seasonal variations not only in aerosol particle abundance and composition but also in their impact on clouds (e.g., Willis et al., 2018). These conditions make the Arctic environment particularly challenging to represent in large-scale climate models (e.g.,

Vertical Gradient of Size-Resolved Aerosol Compositions over the Arctic Reveals Cloud Processed Aerosol in-Cloud and above Cloud

“…We observed a link between this minimum and the presence of sulfate and carbonaceous particles. Specifically, we found that the carbonaceous particles were more prevalent in the smaller modal diameters of the accumulation mode, while sulfate particles dominated in the larger modal diameters of the accumulation mode . This bimodal size distribution is typically observed in nonprecipitating clouds. , It is well recognized that aqueous-phase chemistry in cloud droplets can play a substantial role in generating sulfate aerosol. , Moreover, previous studies also observed various sulfate-containing organic particles during summertime Arctic and sulfate-enriched particles in cloud residuals during spring which is in agreement with our observation.…”

“…Specifically, we found that the carbonaceous particles were more prevalent in the smaller modal diameters of the accumulation mode, while sulfate particles dominated in the larger modal diameters of the accumulation mode. 51 This bimodal size distribution is typically observed in nonprecipitating clouds. 16,52 It is well recognized that aqueous-phase chemistry in cloud droplets can play a substantial role in generating sulfate aerosol.…”

Highly Hygroscopic Aerosols Facilitate Summer and Early‐Autumn Cloud Formation at Extremely Low Concentrations Over the Central Arctic Ocean

“…Since the Aitken mode is still present in the droplet residuals and therefore must have activated prior to sampling, possible explanations are that either (1) the peak SS at the onset of the cloud formation was often higher than 1%, which is within the possible range from model simulations presented in Bulatovic et al (2021), or, more likely, (2) the water uptake on those particles is generally too slow for droplet activation to occur in the short residence time of the particles in the CCNC cloud chamber, as previously suggested by Leck and Svensson (2015), or (3) that the drying process evaporated not only water, but also a fraction of the solute, which would affect the residuals ability to reactivate into a droplet, as suggested by Rissler et al (2023). The presence of an Aitken mode in the residuals is unlikely due to sampling artifacts by the GCVI, such as droplet break up, particle capture by wake effect, or ice crystal shattering, which start occurring at larger crystal diameters than those sampled in these events, as extensively discussed in Karlsson et al (2021Karlsson et al ( , 2022.…”

“…Past studies have shown that when accumulation mode particles are too scarce to take up the excess water vapor, Aitken mode particles can activate and maintain the cloud (Bigg & Leck, 2001;Bulatovic et al, 2021;Karlsson et al, 2021;Korhonen et al, 2008;Leck et al, 2002;Lohmann & Leck, 2005), which can lead to high peak supersaturation during the cloud formation potentially exceeding 1% (Bulatovic et al, 2021). A parcel model simulation using aerosol distributions from this expedition was also presented by Karlsson et al (2022) who showed that, given high but not unheard of cooling rates, particles as small as 25 nm in diameter can be activated. Since the highest SS setting of the CCNC was 0.96% during our measurements, it is possible that it was simply not high enough to activate a fraction of the smallest residuals sampled.…”

Microphysics of liquid water in sub-10 nm ultrafine aerosol particles

“…Water is a predominant component of atmospheric aerosol, with mass fraction typically larger than 70% at moderate to high relative humidities (RH > 40%), and plays crucial roles in the formation and growth of aerosol particles (Pierce et al, 2012;Karlsson et al, 2022). For example, aerosol liquid water facilitates the partitioning of gas-phase These results suggest that water in sub-10 nm ultrafine aerosol particles may have properties distinct from those of bulk liquid water.…”