Photolysis rates based on Schumann-Runge band approximations and irradiance measurements

Date

1985-10

Department

Program

Citation of Original Publication

Herman, Jay and J. E. Mentall. "Photolysis rates based on Schumann-Runge band approximations and irradiance measurements." Geophysical Research Letters 12, no. 10 (October 1985): 659-662. https://doi.org/10.1029/GL012i010p00659.

Rights

This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
Public Domain Mark 1.0

Subjects

Abstract

The photolysis rate (J₃) for CF₂Cℓ₂, (F-12) in the stratosphere has been computed for three altitudes using measured solar fluxes from a balloon borne spectrometer. The rate is compared with that obtained by computing the attenuated flux using effective cross sections appropriate for the Schumann-Runge bands (J₁) [Allen and Frederick, 1982]. The result shows that the error in the F-12 photolysis rate caused by using the Allen and Frederick approximation is about 10% (J₁ < J₃) for altitudes between 32 and 38 km with solar zenith angles less than about 62 degrees. For species other than O₂, this implies that the discrepancy in photolysis rates associated with the Schumann-Runge band approximations are not likely to be important. Within the Schumann-Runge band region the computed errors for F-12 photolysis are about 10.5% at 38.13 km and increase with decreasing altitude. If this error applies to O₂ photolysis, there may be the possibility of an incorrect calculation of net odd oxygen production in photochemical models.