Stratospheric determination of O2 cross sections and photodissociation rate coefficients: 191–215 nm

Abstract

Measurements of the transmittance and deposition of solar ultraviolet energy into the middle stratosphere have been made using a balloon‐borne, solar‐pointing spectrometer with both 0.012‐ and 0.10‐nm resolution. The full spectral range (185–311 nm) includes much of the molecular oxygen Schumann‐Runge [B‐X] absorption and the underlying Herzberg [A‐X] continuum, allowing the derivation of atmospherically appropriate effective absorption cross sections for these bands. In addition to verifying the recent laboratory measurements of the Herzberg continuum cross section, an analysis of the O2 transmittance suggests that window regions within the Schumann‐Runge bands (λ≤200 nm) may also allow deeper penetration of solar energy than predicted by current photochemical modeling schemes.