Revealing the chemical characteristics of Arctic low-level cloud residuals – in situ observations from a mountain site

Gramlich, Yvette; Siegel, Karolina; Haslett, Sophie L.; Freitas, Gabriel; Krejci, Radovan; Zieger, Paul; Mohr, Claudia

doi:10.5194/egusphere-2022-1395

Cited by 2 publications

(4 citation statements)

References 31 publications

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“…where only particles larger than around 100 nm are generally able to activate to cloud droplets. Gramlich et al (2022) came to the same conclusion by performing chemical analyses of aerosol particles and gases before, during and after cloud, without noting strong variations in chemical composition. CCN are typically associated with accumulation mode particles; however, much smaller particles can activate to cloud droplets if the supersaturations developed in clouds are high enough.…”

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confidence: 56%

Aerosol and dynamical contributions to cloud droplet formation in Arctic low-level clouds

Motos¹,

Freitas

Georgakaki³

et al. 2023

Preprint

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Abstract. The Arctic is one of the most rapidly warming regions of the globe. Low-level clouds and fog modify the energy transfer from and to space and play a key role in the observed strong Arctic surface warming, a phenomenon commonly termed "Arctic amplification". The response of low-level clouds to changing aerosol characteristics throughout the year is therefore an important driver of Arctic change that currently lacks sufficient constraints. As such, during the NASCENT campaign (Ny-Ålesund AeroSol Cloud ExperimeNT) extending over a full year from October 2019 to October 2020, microphysical properties of aerosols and clouds were studied at the Zeppelin station (475 m a.s.l.), Ny-Ålesund, Svalbard, Norway. Particle number size distributions obtained from differential mobility particle sizers as well as chemical composition derived from filter samples and an aerosol chemical speciation monitor were analyzed together with meteorological data, in particular vertical wind velocity. The results were used as input to a state-of-the-art cloud droplet formation parameterization to investigate the particle sizes that can activate to cloud droplets, the levels of supersaturation that can develop, the droplet susceptibility to aerosol and the role of vertical velocity. We evaluate the parameterization and the droplet numbers calculated through a droplet closure with in situ measurements. A remarkable finding is that, for the clouds sampled in situ, closure is successful in mixed-phase cloud conditions regardless of the cloud glaciation fraction. This suggests that secondary ice production through ice-ice collisions or droplet-shattering may explain the high ice fraction, as opposed to rime-splintering that would significantly reduce the cloud droplet number below levels predicted by warm cloud activation theory. We also show that pristine-like conditions during fall led to clouds that formed over an aerosol-limited regime, with high levels of supersaturation (generally around 1 %, although highly variable) that activate particles smaller than 20 nm in diameter. Clouds formed in the same regime in late spring and summer, but aerosol activation diameters were much larger due to lower cloud supersaturations (c.a. 0.5 %) that develop because of higher aerosol concentrations and lower vertical velocities. The contribution of new particle formation to cloud formation was therefore strongly limited, at least until these newly formed particles started growing. However, clouds forming during the Arctic haze period (winter and early spring) can be limited by updraft velocity, although rarely, with supersaturation levels dropping below 0.1 % and generally activating larger particles (20 to 200 nm), including pollution transported over a long range. The relationship between updraft velocity and the limiting cloud droplet number agrees with previous observations of various types of clouds worldwide, which tends to confirm the universality of this relationship.

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confidence: 56%

Aerosol and dynamical contributions to cloud droplet formation in Arctic low-level clouds

Motos¹,

Freitas

Georgakaki³

et al. 2023

Preprint

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“…These cloudy periods also correspond to the time with the highest RH values, hence, this demonstrates that cloudy and wet conditions do reduce HPMTF (g) levels in the atmosphere in Svalbard during summer. However, we did not detect HPMTF nor any of its possible reaction products (e.g., C2H4SO2, C2H6SO2) (Jernigan et al, 2022) in significant amounts in any of the cloud residual samples (data not shown) (Gramlich et al, 2022). Therefore, we cannot make a conclusive statement about the fate of HPMTF in the particle phase with our dataset.…”

Section: Correlation Of Hpmtf (G) With Visibility and Relative Humiditymentioning

confidence: 55%

“…Hence, it is difficult to conclude whether the RH or air mass origin is the main reason for the lower HPMTF (g) concentration at high RH. However, during the cloud events studied in Gramlich et al (2022), HPMTF (g) levels were lower compared to right before and right after the cloudy period (Fig. 5c).…”

Section: Correlation Of Hpmtf (G) With Visibility and Relative Humiditymentioning

confidence: 86%

“…Since the particle-phase data was time-integrated and normalized to the sampled volume, the unit is therefore [number of detected ions per liter of sampled air], and the data can be used in the same way as the gas-phase data (qualitative analysis and for relative quantification between measured particulate compounds). More details on the processing of the particle-phase data is given by Gramlich et al (2022).…”

Section: Data Processingmentioning

confidence: 99%

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Arctic observations of Hydroperoxymethyl Thioformate (HPMTF) – seasonal behavior and relationship to other oxidation products from Dimethyl Sulfide at the Zeppelin Observatory, Svalbard

Siegel

Gramlich

Haslett

et al. 2023

Preprint

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Abstract. Dimethyl sulfide (DMS), a gas produced by phytoplankton, is the largest source of atmospheric sulfur over marine areas. DMS undergoes oxidation in the atmosphere to form a range of oxidation products, out of which methanesulfonic acid (MSA) and sulfuric acid (SA) are well-known for participating in the formation and growth of atmospheric aerosol particles. Recently, a new oxidation product of DMS, hydroperoxymethyl thioformate (HPMTF) was discovered and later also measured in the atmosphere. Little is still known about the fate of this compound and its potential to partition to the particle phase. In this study, we present a full year (2020) of concurrent gas- and particle-phase observations of HPMTF, MSA, SA and other DMS oxidation products at the Zeppelin Observatory (Ny-Ålesund, Svalbard) located in the Arctic. This is the first time HPMTF has been measured in Svalbard and attempted to be observed in atmospheric particles. The results show that gas-phase HPMTF concentrations largely follow the same pattern as MSA during the sunlit months (April–September), indicating production of HPMTF around Svalbard. However, HPMTF was not observed in significant amounts in the particle phase, despite high gas-phase levels. Particulate MSA and SA were observed during the sunlit months, although the highest median levels of particulate SA were measured in February, coinciding with the highest gaseous SA levels with assumed anthropogenic origin. We further show that gas- and particle-phase MSA and SA are coupled in May–July, whereas HPMTF lies outside of this correlation due to the low particulate concentrations. These results provide more information about the relationship between HPMTF and other DMS oxidation products in a part of the world where these have not been explored yet, and about HPMTF’s ability to contribute to particle growth and cloud formation.

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Revealing the chemical characteristics of Arctic low-level cloud residuals – in situ observations from a mountain site

Cited by 2 publications

References 31 publications

Aerosol and dynamical contributions to cloud droplet formation in Arctic low-level clouds

Aerosol and dynamical contributions to cloud droplet formation in Arctic low-level clouds

Arctic observations of Hydroperoxymethyl Thioformate (HPMTF) – seasonal behavior and relationship to other oxidation products from Dimethyl Sulfide at the Zeppelin Observatory, Svalbard

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