Stratospheric aerosol properties and their effects on infrared radiation

Abstract

This paper presents a stratospheric aerosol model and infers its effects on terrestrial radiation. Composition of the aerosol is assumed to be concentrated sulfuric acid. An appropriate size distribution has been determined from available size distribution measurements of other investigators. Aerosols composed of concentrated sulfuric acid emit energy in the atmospheric window region of the infrared spectrum, 8–13 μm. Laboratory measurements of optical constant data obtained at room temperature are presented for 75 and 90% aqueous sulfuric acid. Calculations of an aerosol extinction coefficient βext(λ) in km−1 are then performed by using the above data. Peaks in βext(λ) occur at 11.0, 10.3, and 9.6 μm for sulfuric acid aerosol composed mainly of Aitken size particles. Effects of changes in aerosol phase and temperature are discussed but not resolved.

Stratospheric aerosol size distribution.

“…These mass densities are 2 to 5 times as large as those observed by LAZRUs et al (1971) using aircraft sampling, but are 2 orders of magnitude as small as those required to account for downward directed infrared irradiance observed by PILIPOWSKYJ et al (1968).…”

“…(17), with Aitken nuclei in the range 0.03-0.05 pm, of which log radius-number distribution is constant. REMSBERG (1973) presents similar bimodal aerosol model and infers its effects on terrestial radiation.…”

“…PILIPOWSKYJ et al (1968) investigated stratospheric aerosol size distributions by laser radar backscattering and downward directed infrared measurements. Aerosol size distributions for particles larger than 0.1 pm, which were employed for the analysis of other optical measurements, yield results which are consistent with laser radar observations.…”

An Estimation of the Radiative Effect in the Stratosphere due to the Pinatubo Aerosol

“…BCKGD aerosol is composed of a 75% solution of sulfuric acid in water (Rosen, 1971;Toon and Pollack, 1973) and its complex refractive index is based on the measurements of Remsberg (1973), and Palmer and Williams (1975). The size distribution is chosen to be consistent with the concentrations of particles with diameters greater than 0.3 and 0.5am Rosen and Hofmann, 1975) and the concentration of condensation nuclei, i.e., radius smaller than 0.1um, (Rosen et al, 1974;Kaselau et al, 1974).…”

Venus cloud properties: Infrared opacity and mass mixing ratio

“…Young and Young (1973), Sill (1972]. The complex refractive index of H 2 SO 4 has been obtained in the laboratory by Remsberg (1973) over the wavenumber interval 747 to 1570 cm -1 for two concentrations, 75% and 90%. Only the 75% solution shall be considerdd because, as Young (1974) has pointed out, the 90% solution quite clearly shows a qualitatively incorrect wavenumber dependence of the opacity.…”