CLOUD discovers new way by which aerosols rapidly form and grow at high altitude

Posted: May 19, 2022 by oldbrew in Agriculture, atmosphere, climate, Clouds, Emissions, modelling, research


Ammonia in the upper troposphere originates from livestock and fertiliser emissions, say the researchers. CERN says “anthropogenic ammonia has a major influence on atmospheric aerosol particles”. Implications for climate models are suggested.
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Aerosol particles can form and grow in Earth’s upper troposphere in an unexpected way, reports the CLOUD collaboration in a paper published today in Nature.

The new mechanism may represent a major source of cloud and ice seed particles in areas of the upper troposphere where ammonia is efficiently transported vertically, such as over the Asian monsoon regions.

Aerosol particles are known to generally cool the climate by reflecting sunlight back into space and by making clouds more reflective. However, how new aerosol particles form in the atmosphere remains relatively poorly known.

“Newly formed aerosol particles are ubiquitous throughout the upper troposphere, but the vapours and mechanisms that drive the formation of these particles are not well understood,” explains CLOUD spokesperson Jasper Kirkby. “With experiments performed under cold upper tropospheric conditions in CERN’s CLOUD chamber, we uncovered a new mechanism for extremely rapid particle formation and growth involving novel mixtures of vapours.”

Using mixtures of sulfuric acid, nitric acid and ammonia vapours in the chamber at atmospheric concentrations, the CLOUD team found that these three compounds form new particles synergistically at rates much faster than those for any combination of two of the compounds.

The CLOUD researchers found that the three vapours together form new particles 10–1000 times faster than a sulfuric acid–ammonia mixture, which, from previous CLOUD measurements, was previously considered to be the dominant source of upper tropospheric particles. Once the three-component particles form, they can grow rapidly from the condensation of nitric acid and ammonia alone to sizes where they seed clouds.

Moreover, the CLOUD measurements show that these particles are highly efficient at seeding ice crystals, comparable to desert dust particles, which are thought to be the most widespread and effective ice seeds in the atmosphere. When a supercooled cloud droplet freezes, the resulting ice particle will grow at the expense of any unfrozen droplets nearby, so ice has a major influence on cloud microphysical properties and precipitation.

The CLOUD researchers went on to feed their measurements into global aerosol models that include vertical transport of ammonia by deep convective clouds. The models showed that, although the particles form locally in ammonia-rich regions of the upper troposphere such as over the Asian monsoon regions, they travel from Asia to North America in just three days via the subtropical jet stream, potentially influencing Earth’s climate on an intercontinental scale.

“Our results will improve the reliability of global climate models in accounting for aerosol formation in the upper troposphere and in predicting how the climate will change in the future,” says Kirkby. “Once again, CLOUD is finding that anthropogenic ammonia has a major influence on atmospheric aerosol particles, and our studies are informing policies for future air pollution regulations.”

Atmospheric concentrations of sulfuric acid, nitric acid and ammonia were much lower in the pre-industrial era than they are now, and each is likely to follow different concentration trajectories under future air pollution controls.

Ammonia in the upper troposphere originates from livestock and fertiliser emissions – which are unregulated at present – and is carried aloft in convective cloud droplets, which release their ammonia upon freezing.

Full article here.
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Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation. Nature, doi:10.1038/s41586-022-04605-4 (2022).

Comments
  1. […] CLOUD discovers new way by which aerosols rapidly form and grow at high altitude […]

  2. Jaime Jessop says:

    I wonder if this might partly explain the apparent proliferation of persistent contrails which an increasingly vocal element of society insist are ‘chemtrails’?

  3. Gamecock says:

    “Once again, CLOUD is finding that anthropogenic ammonia has a major influence on atmospheric aerosol particles, and our studies are informing policies for future air pollution regulations.”

    No, you got some ammonia to form in your cloud chamber. Therefore, we have to end farming.

  4. gbaikie says:

    I thought we are living in Ice Age and we wanted cooling for some reason.

  5. Phoenix44 says:

    10-1000 times faster?

    That’s quite a range. Not the most convincing result.

  6. oldbrew says:

    From gov.uk
    Do contrails impact on climate change?

    Persistent contrail cirrus, formed by aircraft, can affect the reflection of solar radiation and therefore have an impact on the Earth’s climate.

    The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018 suggests that the present climate impact of contrail cirrus is larger than that from historical emissions of greenhouse gases emitted by aircraft.

    However, this research also notes that significant uncertainties remain in understanding the full impact of contrail cirrus due to the complexity of the physics of its formation and how it may cause climate change.

    https://www.gov.uk/government/publications/contrails-and-chemtrails-frequently-asked-questions/contrails

  7. Gamecock says:

    “and therefore have an impact on the Earth’s climate”

    Earth doesn’t have a climate. It has many climates. They parade their ignorance.

  8. oldbrew says:

    significant uncertainties remain

    UK gov’s third paragraph partly contradicts/undermines the other two.

  9. catweazle666 says:

    So, where does that leave the novel theory that liquid ammonia is going to replace kerosene as jet fuel?

    It seems that there are pilot schemes running now, courtesy of FLOP26.

    https://www.ammoniaenergy.org/articles/nasa-boeing-ucf-to-study-zero-carbon-ammonia-jet-fuel/#:~:text=Ammonia%20in%20jet%20engines&text=At%20COP26%20last%20year%2C%20a,aviation%20applications%20(amongst%20others).

  10. Scott says:

    Is there a link at all to mare’s tails and/or mackerel’s scales?

  11. oldbrew says:

    catweazle666 says: ‘where does that leave the novel theory that liquid ammonia is going to replace kerosene as jet fuel?’

    Good question.

  12. Gamecock says:

    Ammonia, when evaluated for powering ships, was determined to have 40% of the energy content of bunker crude. Yes, ammonia could be used, but you’d need 2.5X more. A serious problem in shipping. A show stopper for airplanes.

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