Photodissociation of nitric oxide in the middle and upper atmosphere

Absorption of solar radiation at wavelengths between 175 to 205 nm plays a fundamental role in the photochemistry of the middle atmosphere. Nitric oxi de photodissociates in the delta (0-0) and delta (1-0) bands near 191 and 1 83 nm, respectively, initiating the primary mechanism for NO, removal in th e middle atmosphere. The spectrally rich Schumann-Runge (S-R) bands of O-2 are the main source of atmospheric opacity at these wavelengths. A re-evalu ation of O-2 absorption has been made based on recent advances in understan ding of S-R line shapes, leading to differences with conventional approache s assuming Voigt line profiles in line-by-line calculations of the O-2 cros s section. The new results are used to examine the impact of O-2 transmissi on on the photodissociation of NO in the delta (0,0) and delta (1,0) bands. (C) 2001 Elsevier Science Ltd. Ali rights reserved.