Radiation Absorption by Droplets of Sulfuric Acid Water Solutions and by Ammonium Sulfate Particles

The absorption spectra of 49% 73% and 98% sulfuric acid water solutions for wavelengths of 0.3–6.5.μ and those of ammonium sulfate for 0.3–25 μ are either measured for the purposes of this study or quoted from the literature. Sulfuric acid water solutions have an absorption in the range 1.6–6.5μ. Absorption by 49% and 73% solutions is particularly strong. It is much stronger than absorption by liquid water over most of the range. Ammonium sulfate has no absorption of any significance from 0,3 to 2.85μ but has four absorption bands in the range 2.85-25μ, the largest absorption occurring at about 9.25μ in the terrestrial radiation “window.” The conclusions are as follows: 1) sulfuric acid water solution droplets will absorb solar radiation in the near IR, about 2μ 2) ammonium sulfate particles will not absorb solar radiation; and 3) both will, of course, scatter solar radiation. The above results are relevant to the absorption of solar radiation by droplets or by solid particles in the lower stratosphere as well as to a similar absorption in the lower atmosphere of industrially polluted areas.