Article

Review
2022. V. 60. № 4. P. 536–569
Smirnov B.M., Son E.E.
Electric processes in atmospheric air
Annotation
The article presents a physical picture of electrical processes in the atmosphere, based on atmospheric measurements and physical laws. Some processes of atmospheric electricity associated with water microdroplets in the atmosphere are analyzed. It is shown that microdroplets acquire a charge in their growth process, and the loss of charge by microdroplets, which occurs at the lower boundary of a cumulus cloud, leads to breakdown in the form of lightning, accompanied by rapid (within minutes) aggregation of cumulus cloud microdroplets into raindrops. Representing the electrical processes in the atmosphere as secondary with respect to water circulation through the atmosphere, we find that water condensation in the atmosphere results from the mixing of moist the near-surface air layers with cold air at altitudes of several kilometers under vertical wind action. The dominant droplet growth mechanisms are coalescence for small droplets and gravitational fall for large droplets. In this case, equilibrium between cumulus cloud water microdroplets and saturated vapor of free molecules is established in a fraction of a second; i.e., this equilibrium is maintained during the evolution of the cumulus cloud. This means that the water vapor inside the cumulus cloud is saturated. The droplet charging mechanism is similar to this process in plasma and is governed by the varying mobility of positive and negative ions in atmospheric air, while the ions themselves in it form under the action of cosmic rays. Atmospheric water microdroplets are also a greenhouse component of the atmosphere. Analysis of the thermal radiation of atmospheric water microdroplets, in addition to the energy balance of the Earth and atmosphere, makes it possible to estimate the fraction of condensed water in the atmosphere, the mass of which is a fraction of a percent of the mass of atmospheric water vapor in the form of free water molecules. At the same time, clouds are a heterogeneous medium, so that areas in the atmosphere containing water microdroplets exist in the atmosphere as separate clusters. Although analysis of the water microdroplet behavior in cumulus clouds allows us to answer certain questions on the physics of atmospheric electricity, other aspects of this problem retain a schematic character and require further study.
Article reference:
Smirnov B.M., Son E.E. Electric processes in atmospheric air, High Temp., 2022. V. 60. № 4. P. 536