<title>Ultraviolet O<formula><inf><roman>2</roman></inf></formula> transmittance - AURIC implementation</title>

Abstract

The rich spectral structure of the UV Schumann-Runge bands of molecular oxygen have historicaliy been difficult to parameterize for rapid atmospheric photochemical modeling calculations. Stratospheric odd oxygen production and dissociation of trace compounds are particularly sensitive to the accuracy of the adopted algorithms. A new spectrally precise approach to Schumann-Runge synthesis has been devised, employing nine (9) different spectral arrays (at 0.5 cm1 spacing between 49,000 and 57,000 cm1) containing polynomial coefficients. The coefficients were fit to calculated cross sections obtained from a detailed Schumann-Runge model that incorporates the most recent high resolution spectroscopic data for a temperature range between 130 and 500K.This large (but straightforwardly implemented) data base is being used to reexamine the existing parameterizations of UV transmission and photolysis. In addition, it is now possible to extend atmospheric radiance codes (such as LOWTRAN 1,2 and its derivative MODTRAN3) further into the ultraviolet. Initial implementation has been accomplished for the MODTRAN code as part of the eventual development of AURIC, the Atmospheric Ultraviolet Radiance Integrated Code.