Effects of PSC (Polar Stratospheric Clouds) on the Photodissociation Processes of Atmospheric Trace Gases

Abstract

Photodissociation rate of atmospheric minor constituents in antarctic winter was studied on the numerical model including spherical atmosphere effect and taking it into consideration that the scattering effect of PSC (Polar Stratospheric Clouds) on photodissociation. Diffusion of solar radiation into the lower stratosphere was suggested during antarctic winter period. Therefore significant photodissociation is expected even in winter time. For example, the ratio of the photodissociation rate at solar zenith angle θ₀ = 90 ° to that at θ₀ = 60 ° for Chappius band of ozone is 59.2 %. Within the value for PSC, 8 % increase of flux was found at wavelength λ =755 nm comparing the value for PSC free condition for θ₀ = 80 °, and photodissociation rates of ozone (Chappius band), ClONO₂, and HOCl showed a 2 % increase. However, a 2 % decrease in the rate was found for O₂. Summarizing the results of calculation, the effect of PSC on the photo- dissociation process can advance even in antarctic winter.