Abstract
A previous analysis of the energy balance of small particles in the earth's atmosphere is extended to substances that have special significance in the stratospheric aerosol layer, such as sulphuric acid and volcanic ash. The analysis is based on establishing a balance between the power absorbed by the particles from solar and planetary radiation fields, the power emitted by the particles as thermal radiation and the power exchanged through collisions with the ambient gas. The planetary radiation field is calculated as a function of altitude and includes radiation from the surface as well as emission and absorption by the infrared bands of carbon dioxide, ozone and water vapour. The various terms in the energy balance equation change as a function of the composition, radius and altitude of the aerosol particles, and of the latitude, season, time of day and albedo of the underlying earth‐atmosphere system; aerosols may heat or cool the atmosphere and their temperature may differ from the ambient gas temperature. Average values for rates of heating induced in the ambient gas by monodisperse and polydisperse aerosol particles are computed for various substances. The rates of heating induced by volcanic ash particles and sulphuric acid droplets are calculated for equatorial, mid‐latitude summer and mid‐latitude winter conditions for altitudes to 40 km.
Our results illustrate the effects on atmospheric heating rates of changing the size distribution of the particles and the particle composition. We also show that heating rates of at least 0.25 K day^−1^ were induced by the stratospheric aerosol layer after the 1963 eruption of the Gunung Agung volcano in Bali.