New information on the role of insoluble dust particles in the cloud droplets form could improve the accuracy of regional climate models, particularly in regions of the world that have large amounts of mineral aerosols in the atmosphere. More accurate accounting for the role of these particles may also have implications for global climate models.
Properties of clouds can have a significant impact on climate, but the effects of aerosols and dust is one of the most uncertain climate models. Scientists have recognized the importance of soluble particles such as sea salt and sulphates, the creation of small droplets that form clouds and cause precipitation. But so far, the role of insoluble particles - especially the sweeping dust into the atmosphere from sources such as deserts - has not figured significantly in climate models.
Using a combination of physics-based theory and laboratory measurements are the heart, researchers at the Georgia Institute of Technology have developed a model that can be added to existing regional or global climate simulations. These activities affect cloud condensation nuclei enhancements (CCN), activity and kinetics of activation of the drops is still under investigation.
"Understand that the insoluble powder drops than we thought it might be, and the drops that form near the source of particles that could change our understanding of how precipitation formed in regions like the Mediterranean, Asia and other climate -stressed areas, "said Athanasios Nenes, professor of the Faculty of Earth and Atmospheric Sciences, Georgia Institute of Technology.
The research was supported by the National Science Foundation (NSF), National Oceanic and Atmospheric Administration (NOAA) and NASA. The results described in the 2011 autumn meeting of the American Chemical Society in Denver, and reported in journals Geophysical Research Letters, Journal of Geophysical Research and the Atmospheric Chemistry and Physics. New book on modeling the effects of the world has been accepted for publication in the Journal of Geophysical Research.
Soluble nuclear particles drop through the absorption of water under high humidity. Insoluble materials, as dust can not absorb water, so we thought we played a minor role in the formation of clouds and precipitation.
However, Nenes and partners, I realized that these dust particles would nucleate droplets in a different way - absorbing moisture on their surface, moisture condenses a lot of window glass during changes in temperature. Some of the insoluble particles of clay materials can also absorb moisture, even if they do not dissolve in it.
Work with Irina Sokolik, a professor in the School of Earth and Atmospheric Sciences, Nenes and graduate student Prashant Kumar studied the aerosol particles generated from desert soil samples from several regions, including Africa North East Asia / China and North America. In laboratory conditions simulating those of a saturated atmosphere, the insoluble particles formed cloud droplets, but the process was slower than the droplets produced from soluble materials.
laboratory materials found in the atmosphere, "said Nenes, who also has a professorship at the Georgia Tech School of Chemical and Biomolecular Engineering." These particles absorb water by using a mechanism that had not been previously considered in the models. It turns out that this process of adsorption of water absorbs enough to form cloud droplets. "
Laboratory work has shown that smaller particles are more likely than expected to generate drops, and its effectiveness as condensation nuclei of clouds is affected by the type of minerals present, their size, morphology and processes affecting the atmosphere. Dust particles ranging in size from 100 nanometers to several microns.
These mineral aerosols can consist of iron oxides, carbonates, quartz and clay. Mainly from arid and semi-arid and can remain airborne for as long as several weeks, allowing them to be transported long distances from their sources. In the atmosphere, dust particles tend to accumulate soluble materials as they age.
"We can simulate what happens to the particles as they slowly covered with more and more soluble materials," said Nenes. "As more and more soluble in the coating, they become more hygroscopic."
The researchers are now working with collaborators in Germany, to integrate their new theories in existing climate models to see how you can make predictions. We also hope to make a new field work to measure the activity of these insoluble aerosols in real conditions.
"Now we must study the cloud particles in the atmosphere and their ability to form droplets to verify our theory using data from real weather," said Nenes. "We also look at dust and clouds in most parts of the world to ensure that the theory works for everyone."
Clouds play an important role in the climate of Directors, to add new information about training can improve the accuracy of complex climate models.
"The reason we worry about the particle-cloud interactions is that they introduce many uncertainties in predictions of climate models," said Nenes. "Everything that can be done to improve these predictions by providing Specifically cloud data would be useful to predict climate change. "
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