Ice-nucleating agents in sea spray aerosol identified and quantified with a holistic multimodal freezing model

Alpert, Peter A.; Kilthau, W.; O’Brien, Rachel E.; Moffet, Ryan C.; Gilles, Mary K.; Wang, Bingbing; Laskin, Alexander; Aller, Josephine Y.; Knopf, Daniel A.

doi:10.1126/sciadv.abq6842

Cited by 20 publications

(24 citation statements)

References 80 publications

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“…This closure approach will be applied also within the planned MOSAiC studies (to be presented in follow-up articles). In the first step, the ice-nucleation rate J het is computed as a function of SSA specific parameters k = 26.6132 and b = -3.9346 (Alpert et al, 2022) and for a given ice-nucleation temperature and ice supersaturation S ICE . The product of s dry × J het × ∆t then yields n INP .…”

Section: Arctic Aerosol Of Continental Originmentioning

confidence: 99%

“…These recent findings point to a strong role of biogenic INPs in Arctic ice nucleating processes in summer. Alpert et al (2022) present an INP parameterization to estimate INPs concentrations for sea spray aerosol, applicable to lidar observations. While soil dust particles most likely dominate ice nucleation in the lower troposphere (<2.5 km) in winter, when cloud top temperatures in mixed-phase clouds are usually far below −15 to −20°C, local INPs of biogenic origin seem to control ice nucleation in the boundary layer in summer when cloud top temperatures in mixed-phase clouds with typical top heights below 2.5 km are usually > −15°C (Griesche et al, 2021;Creamean et al, 2022).…”

mentioning

confidence: 99%

“…2.8.2 Sea spray aerosol (SSA) in the summer ABL Recently,Alpert et al (2022) introduced a parameterization that permits the estimation of SSA INP concentrations caused by biogenic aerosol components. These INPs may be responsible for the observed ice nucleation in the summer ABL at high temperatures > −10 to −15°C(Griesche et al, 2021), at which mineral dust particles are no longer efficient INPs.…”

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confidence: 99%

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Annual cycle of aerosol properties over the central Arctic during MOSAiC 2019–2020 — light-extinction, CCN, and INP levels from the boundary layer to the tropopause

Ansmann

Ohneiser

Engelmann

et al. 2023

Preprint

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Abstract. Continuous height-resolved observations of aerosol profiles over the central Arctic throughout a full year were performed for the first time. Such measurements covering aerosol layering features are required for an adequate modeling of Arctic climate conditions, especially with respect to a realistic consideration of cloud formation and here, in particular, of ice nucleation processes. MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) offered this favorable opportunity to monitor aerosol and clouds over the central Arctic over all four seasons, from October 2019 to September 2020. In this article, a summary of MOSAiC lidar observations aboard the icebreaker Polarstern of tropospheric aerosol products is presented. Particle optical properties, i.e., light-extinction profiles and aerosol optical thickness (AOT), and estimates of cloud-relevant aerosol properties (cloud condensation nucleus, CCN, and ice-nucleating particle concentrations, INPs) are discussed, separately for the lowest part of the troposphere (near the surface at 250 m height), within the lower free troposphere (2000 m height), and regarding INPs also near the tropopause (cirrus level, 8–10 km height). In situ observations of the particle number concentration and INPs aboard Polarstern are included in the study. Strong differences between summer and winter aerosol conditions were found. During the winter months (Arctic haze period) a strong decrease of the aerosol light extinction coefficient (532 nm) with height up to about 4–5 km height was found with values of 20–100 Mm-1 close to the surface and an order of magnitude less at 1500–2000 m height. Lofted aged wildfire smoke layers caused a re-increase of the aerosol concentration from the middle troposphere up to stratospheric heights and were continuously observable from October 2019 to May 2020. In summer (June to August 2020), much lower particle extinction coefficients, frequently as low as 1–5 Mm-1, were observed. Aerosol removal, controlled by cloud scavenging processes (widely suppressed in winter, very efficient in summer) in the lowermost 1–2 km of the atmosphere, seem to be the main reason for the strong differences between winter and summer aerosol conditions. In line with this pronounced annual cycle in the aerosol optical properties, CCN concentrations (0.2 % supersaturation level) ranged from 50–500 cm-3 in the atmospheric boundary layer (ABL) in winter and 1–40 cm-3 in summer. In the lower free troposphere, however, the CCN level was roughly constant throughout the year with values mostly from 30–100 cm-3. A strong contrast between winter to summer was also given in terms of ABL INPs which control ice production in low-level clouds. INP concentration of 0.01–0.2 L-1 prevailed in the ABL in winter at typical ice-nucleating cloud temperatures of -25 °C and assuming soil dust as the main INP type, and were roughly 2 orders of magnitude lower in the ABL in summer at typical cloud top temperatures of -10 °C. In the summer ABL, marine aerosol (biogenic components) is most probably the main INP type, continental INP contributions (e.g., soil dust INPs) are suppressed by efficient wet removal during long-range transport. A strong reduction in the INP population was also found in the lower free troposphere at 2000 m height from winter to summer (2 orders of magnitude), mostly due to the change in the prevailing ice-nucleation temperatures. Estimated INP concentration accumulated from 0.004–0.02 L-1 during the winter months. The highlight of the MOSAiC lidar studies was the detection of a persistent wildfire smoke layer in the upper troposphere and lower stratosphere from October 2019 to May 2020. The smoke particles (organic aerosol) triggered continuously cirrus formation at INP concentrations mostly from 1–20 L-1 close to the tropopause during the entire winter period.

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Section: Arctic Aerosol Of Continental Originmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Annual cycle of aerosol properties over the central Arctic during MOSAiC 2019–2020 — light-extinction, CCN, and INP levels from the boundary layer to the tropopause

Ansmann

Ohneiser

Engelmann

et al. 2023

Preprint

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“…Support for this consideration comes from studies that analyzed ambient particle populations and INPs micro-spectroscopically on an individual particle level (Knopf et al, 2018;Laskin et al, 2016). Those studies find that the INPs are chemically and morphologically not significantly different than particles that do not act as INPs (Alpert et al, 2022;China et al, 2017;Hiranuma et al, 2013;Knopf et al, 2014Knopf et al, , 2018Lata et al, 2021), consistent with a stochastic freezing process (i.e., one particle out of many same ones induced freezing). Consequently, in the ABIFM case, for each modeling time step, the number of activatable INPs is reassessed taking the entire activatable aerosol population into account (since special INPs are not assigned).…”

Section: Conceptual Approachmentioning

confidence: 99%

A 1D Model for Nucleation of Ice From Aerosol Particles: An Application to a Mixed‐Phase Arctic Stratus Cloud Layer

Knopf,

Silber,

Riemer

et al. 2023

J Adv Model Earth Syst

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Mixed‐phase clouds (MPCs) have been identified as significant contributors to uncertainties in climate projections, attributable to model representation of processes controlling the formation and loss of supercooled water droplets and ice particles from the atmosphere. Arctic MPCs are commonly widespread and long‐lived, with sustained ice crystal formation processes that challenge current understanding. This study examines the ice‐nucleating particle (INP) reservoir dynamics governing immersion‐mode heterogeneous freezing in an observed case of Arctic MPCs using a simplified 1D aerosol‐cloud model. The model setup includes prescribed dynamical forcings and thermodynamic profiles, and represents INPs as multicomponent and polydisperse particle size distributions. Diagnostic and prognostic approaches to immersion freezing parameterization are compared, including time‐independent (singular) number‐ and surface area‐based descriptions and a time‐dependent description following classical nucleation theory (CNT). The choice of freezing parameterization defines the size of the INP reservoir. The CNT‐based description yields an orders of magnitude larger INP reservoir than the singular parameterizations, which is the dominant factor for sustained ice crystal formation. The efficiency of the freezing process and cloud cooling are of secondary importance. A diagnostic treatment neglecting INP loss is only accurate when the INP reservoir size is large and INP depletion weak. Since a larger INP reservoir sustains ice crystal formation substantially longer, and ice water path scales with ice crystal concentrations for the conditions considered, resolving the source of differences in INP reservoir dynamics due to model implementation is a high priority for advancing climate model physics.

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“…For example, mineral dust particles with large emission rates of up to 5000 Tg yr –1 are recognized as the most important INP type because of their generally effective ice nucleation ability. − Previous studies have found that dust particles activate as ice crystals at temperatures above −15 °C in the immersion mode . Additionally, biological aerosols including bacteria, pollen, viruses, fungi, and phytoplankton can also act as effective INPs with freezing temperatures ranging from −3 °C for bacteria to below −38 °C for marine aerosols. − Furthermore, many studies have shown the pervasive presence of ammonium sulfate and sulfuric acid particles in the upper troposphere. These particles exhibit homogeneous freezing temperatures below −38 °C, playing a significant role in the formation of cirrus clouds. − …”

Section: Introductionmentioning

confidence: 99%

Effect of Acidity on Ice Nucleation by Inorganic–Organic Mixed Droplets

Lei,

Chen,

Brooks

2023

ACS Earth Space Chem.

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Aerosol acidity significantly influences heterogeneous chemical reactions and human health. Additionally, acidity may play a role in cloud formation by modifying the ice nucleation properties of inorganic and organic aerosols. In this work, we combined our well-established ice nucleation technique with Raman microspectroscopy to study ice nucleation in representative inorganic and organic aerosols across a range of pH conditions (pH −0.1 to 5.5). Homogeneous nucleation was observed in systems containing ammonium sulfate, sulfuric acid, and sucrose. In contrast, droplets containing ammonium sulfate mixed with diethyl sebacate, poly(ethylene glycol) 400, and 1,2,6-hexanetriol were found to undergo liquid–liquid phase separation, exhibiting core–shell morphologies with observed initiation of heterogeneous freezing in the cores. Our experimental findings demonstrate that an increased acidity reduces the ice nucleation ability of droplets. Changes in the ratio of bisulfate to sulfate coincided with shifts in ice nucleation temperatures, suggesting that the presence of bisulfate may decrease the ice nucleation efficiency. We also report on how the morphology and viscosity impact ice nucleation properties. This study aims to enhance our fundamental understanding of acidity’s effect on ice nucleation ability, providing context for the role of acidity in atmospheric ice cloud formation.

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Ice-nucleating agents in sea spray aerosol identified and quantified with a holistic multimodal freezing model

Cited by 20 publications

References 80 publications

Annual cycle of aerosol properties over the central Arctic during MOSAiC 2019–2020 — light-extinction, CCN, and INP levels from the boundary layer to the tropopause

Annual cycle of aerosol properties over the central Arctic during MOSAiC 2019–2020 — light-extinction, CCN, and INP levels from the boundary layer to the tropopause

A 1D Model for Nucleation of Ice From Aerosol Particles: An Application to a Mixed‐Phase Arctic Stratus Cloud Layer

Effect of Acidity on Ice Nucleation by Inorganic–Organic Mixed Droplets

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