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Updated: May 13, 2025
09:34
Extraction and Characterization of Surfactants from Atmospheric Aerosols
Published on: April 21, 2017
16.7K
High sensitivity of cloud formation to aerosol changes.
Annele Virtanen1, Jorma Joutsensaari1, Harri Kokkola1,2
1Department of Technical Physics, University of Eastern Finland, Kuopio, Finland.
Nature Geoscience
|April 14, 2025
Summary
Cloud droplet susceptibility to aerosol particles is higher in low-level clouds than previously thought. This finding impacts estimates of aerosol indirect radiative forcing and highlights model deficiencies.
Area of Science:
- Atmospheric Science
- Climate Science
- Aerosol Science
Background:
- Cloud droplet number concentration is sensitive to cloud condensation nuclei (CCN) number.
- This susceptibility influences aerosol-cloud interactions and radiative forcing, a key uncertainty in climate change projections.
- Low-level stratiform clouds are significant contributors to Earth's radiative balance.
Purpose of the Study:
- To investigate the susceptibility of cloud droplet number to CCN number in low-level stratiform clouds.
- To compare in situ observations with satellite-derived estimates and Earth system model simulations.
- To quantify aerosol indirect radiative forcing based on observational data.
Main Methods:
- Utilized long-term in situ observations (3-10 years) of aerosols and clouds at three high-latitude sites.
- Estimated aerosol indirect radiative forcing from observational data.
- Evaluated four Earth system models against the observational data for susceptibility and underlying physics.
Main Results:
- In situ observations revealed higher cloud droplet susceptibility in low-level stratiform clouds compared to satellite data.
- Estimated aerosol indirect radiative forcing of -1.16 W m⁻² based on observations, aligning with higher-end satellite estimates.
- Significant inter-model variability in susceptibility was found, with underlying physics often deviating from observations.
Conclusions:
- Observed cloud droplet susceptibility suggests a stronger aerosol-cloud interaction effect than often represented in models.
- The study provides a robust observational constraint for aerosol indirect radiative forcing.
- Discrepancies highlight the need to improve sub-grid-scale updraught velocities and aerosol size distribution representations in Earth system models.
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