Ice nucleating ability of black carbon in cirrus regime: effects of morphology, mobility size, mixing state, SOA coating and atmospheric aging
Bibliographic record
Abstract
Black carbon (BC), as potential ice nucleating particles (INPs) in troposphere, can affect cirrus formation and hence global climate. Yet, the IN ability of BC, internally-mixed BC, and BC-seeded secondary organic aerosol (SOA) remain highly uncertain. We have systematically examined the IN ability of (1) size-selected BC with different morphology; (2) BC internally mixed with inorganic salts; (3) BC-seeded SOA from aircraft exhaust (toluene and n-dodecane) and biogenic (β-caryophyllene) volatile organic compound in contrail-cirrus regime (-46 to -38°C). Several aerosolized BC proxies were selected to examine particle morphology at different atmospheric aging stages. Co-atomization of BC and salt solution generated internally-mixed BC particles. SOA coating was generated by a potential aerosol mass (PAM) oxidation flow reactor. IN activity was determined with the Spectrometer for Ice Nuclei (SPIN). Particle number concentration and chemical composition were monitored online by a Condensation Particle Counter (CPC) and Particle Analysis by Laser Mass Spectrometry (PALMS), respectively. SOA composition was also monitored by an Aerosol Mass Spectrometer (AMS). The preliminary results suggest that: (1) the more fractal BC particles don’t necessarily act as superior deposition INP over more spherical ones. The onset of some deposition nucleation, as opposed to purely homogeneous freezing, occurs for some BC types between 100-200 nm; (2) mixing with inorganic salts may partially form hygroscopic sites or salt layers on BC particles. Such particles may deliquesce and form a liquid film, leading to homogeneous rather than heterogeneous ice freezing; (3) n-dodecane and toluene derived SOA nucleate ice through homogeneous freezing only, while β-caryophyllene derived SOA can form ice through deposition ice nucleation. When the relative humidity approaches water saturation, the hygroscopic β-caryophyllene derived SOA may deliquesce and form liquid shells. Such difference in ice nucleation properties may be due to the difference of the chemical composition in SOA coating, highlighting the importance of understanding the aging process of atmospheric BC particles in order to better predict their ice nucleation behaviour and contribution to cirrus cloud formation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".