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Measurement of Aerosols Optical Thickness of the Atmosphere using the GLOBE Handheld Sun Photometer
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Aerosol-cloud-climate cooling overestimated by ship-track data.
Franziska Glassmeier1,2,3, Fabian Hoffmann3,4,5, Jill S Johnson6
1Department of Geoscience and Remote Sensing, Delft University of Technology, P.O. Box 5048, 2600 GA Delft, Netherlands. f.glassmeier@tudelft.nl.
Science (New York, N.Y.)
|January 29, 2021
Summary
Anthropogenic aerosols can alter cloud reflectivity, but ship-track studies overestimate their climate cooling effect. Accounting for reduced cloud amount is crucial for accurate climate projections of aerosol forcing.
Area of Science:
- Atmospheric Science
- Climate Science
- Cloud Physics
Background:
- Anthropogenic aerosols significantly impact climate by altering cloud properties, particularly stratocumulus cloud decks.
- Changes in cloud amount due to aerosol-induced mixing represent a key uncertainty in climate projections.
Purpose of the Study:
- To evaluate the reliability of ship-track studies for estimating the climatological forcing of anthropogenic aerosols on stratocumulus cloud amount.
- To quantify the overestimation of cooling effects derived from ship-track data and assess the impact of cloud amount changes.
Main Methods:
- Comparison of detailed numerical simulations with satellite observations of stratocumulus cloud decks.
- Analysis of aerosol-enhanced cloud-top mixing in nonprecipitating stratocumulus clouds.
Main Results:
- Ship-track studies significantly overestimate the cooling effect of anthropogenic aerosols on stratocumulus clouds by up to 200%.
- Aerosol-induced reduction in stratocumulus cloud amount can offset radiative cooling effects.
Conclusions:
- Ship-track studies are not representative of global, climatological aerosol forcing on stratocumulus.
- Accurate climate forcing assessments require incorporating the warming effect of aerosol-induced decreases in stratocumulus cloud amount.
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