Sea-spray regulates sulfate cloud droplet activation over oceans
This work found that sea-salt controls the activity of sulphate nuclei leading to deviations from monotonicity and are likely to have a greater impact and control of marine clouds on climate, which has significant implications for both basic climate-air pollution and geoengineering communities. The availability of cloud nuclei is thought to monotonically increase cloud top reflectance in marine stratiform clouds. The cloud nuclei are thought to be dominated by sulphate nuclei; however, while this may be the case, we found that sea-salt actually controls the activity of sulphate nuclei leading to deviations from monotonicity and are likely to have a greater impact and control of marine clouds on climate.
Sulfate aerosols are typically the dominant source of cloud condensation nuclei (CCN) over remote oceans and their abundance is thought to be the dominating factor in determining oceanic cloud brightness. Their activation into cloud droplets depends on dynamics (i.e. vertical updrafts) and competition with other potential CCN sources for the condensing water. We present new experimental results from the remote Southern Ocean illustrating that, for a given updraft, the peak supersaturation reached in cloud, and consequently the number of droplets activated on sulfate nuclei, is strongly but inversely proportional to the concentration of sea-salt activated despite a 10-fold lower abundance. Greater sea-spray nuclei availability mostly suppresses sulfate aerosol activation leading to an overall decrease in cloud droplet concentrations; however, for high vertical updrafts and low sulfate aerosol availability, increased sea-spray can augment cloud droplet concentrations. This newly identified effect where sea-salt nuclei indirectly controls sulfate nuclei activation into cloud droplets could potentially lead to changes in the albedo of marine boundary layer clouds by as much as 30%.
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Breakthrough
Sea-Spray Regulates Sulphate Cloud Droplet Activation Over Oceans: This work found that sea-salt controls the activity of sulphate nuclei leading to deviations from monotonicity and are likely to have a greater impact and control of marine clouds on climate, which has significant implications for both basic climate-air pollution and geoengineering communities.
Importance
The availability of cloud nuclei is thought to monotonically increase cloud top reflectance in marine stratiform clouds. The cloud nuclei are thought to be dominated by sulphate nuclei; however, while this may be the case, we found that sea-salt actually controls the activity of sulphate nuclei leading to deviations from monotonicity and are likely to have a greater impact and control of marine clouds on climate. Moreover, the results had a large impact on the potential Marine Cloud Brightening geoengineering initiative.
Translation
Fossum, K.N., Ovadnevaite, J., Ceburnis, D. et al. ‘Sea-spray regulates sulfate cloud droplet activation over oceans’, ‘Climate and Atmospheric Science’: 44 tweets, 11 news articles, Mendeley score of 14, Altmetric score of 98, and 2021 views. The paper is ranked in the 96th percentile of same-age articles across all journals, and the 1st percentile (ranked 1st) for ‘Climate and Atmospheric Science’.
Beneficiaries
This has significant implications for both basic climate-air pollution and geoengineering communities.
To read the full report follow the link: Here
