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Wednesday, October 18, 2017

Physicists have described the birth of a cloud droplet


Physics of National laboratory of Lawrence in Berkeley (USA) have discovered a new mechanism that explains the birth of cloud droplets and can affect the construction of modern climate models of the Earth. Scientists also have elucidated the role of organic aerosols in the process. The study authors published in the journal Science.

Water droplets formed during condensation of steam on aerosol particles at low pressure (at high altitudes). The condensates form drops or ice crystals, which together subsequently form clouds. Aerosols act as centers of condensation of steam, and the dynamics of the process is determined by surface tension.

Physics conducted an experiment the results of which created a model describing the birth of cloud droplets in the atmosphere. The experiments included conditions that occur in air layers of the Earth in the formation of droplets and clouds (aerosol particles, cold air and sunlight).

Physics has defined the scope of the parameters at which begins the formation of drops, in particular, a critical value of the amount of water vapor required for condensation water. The main conclusion of scientists is to elucidate the role of organic and inorganic aerosols in the formation of droplets (in the experience of dicarboxylic acids and ammonium sulfate, respectively).

Scientists have shown that the formation of a large droplet (marked in red in the figure) occurs when organic aerosols are present on the surface of the drop and does not dissolve in it. During the experiments, scientists have observed the birth of straw that were 50-60% larger than predicted by the standard models.

The droplet size influences the brightness: a large number of small drop reflects the sunlight stronger (and, consequently, does not allow to warm the Earth), than the same number of larger drops. As organic aerosols are favored by many anthropogenic compounds, in particular, the products of the combustion of oil. Research scientists need to better predict climate changes on the planet.

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