Photodissociation of molecular oxygen in the terrestrial atmosphere: Simplified numerical relations for the spectral range of the Schumann‐Runge bands

A numerical method is presented for modeling the photodissociation of molecular oxygen in the spectral range 175–200 nm of the Schumann-Runge bands (19–0) to (2–0) in the terrestrial atmosphere. It is possible to obtain realistic photodissociation rates that are in good agreement with detailed and complete calculations by using the following simple formulae: In the thermosphere, JSRB = 1.1 × 10−7 exp [−1.97 × 10−10N0.522] s−1 for N ≤1×1019 O2 molecules cm−2 with a precision better than ±10%, and in the mesosphere, JSRB = 1.45 × 108N−0.83s−1 for N≥15×1019 O2 molecules cm−2 with a precision better than ±15%. The lower boundary conditions can be introduced near the stratopause level with the same precision at 50 km and 45 km as a result of the ozone absorption effect. The upper limit for the formula corresponds to N(O2) = 1022cm−2 with a precision of ±15%. If the solar activity action is characterized by increases of 20%, 15%, 10%, and 5% for the four groups of bands (19–0) to (15–0), (14–0) to (10–0), (9–0) to (6–0), and (5–0) to (2–0), respectively, the photodissociation frequency increases by a factor of 1.15 in the thermosphere and 1.11±0.04 in the mesosphere. The accuracy of the formulae depends on the experimental accuracy of the solar irradiance between 175 and 200 nm and on the parameters (oscillator strengths and line widths) of each Schumann-Runge band.

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