Abstract
Abstract. Based on the zero-dimensional box model Module Efficiently Calculating the Chemistry of the Atmosphere/Chemistry As A Box model Application (CAABA/MECCA-3.72f), an OH airglow model was developed to derive night-time number densities of atomic oxygen ([O(3P)]) and atomic hydrogen ([H]) in the mesopause region (∼75–100 km). The profiles of [O(3P)] and [H] were calculated from OH airglow emissions measured at 2.0 µm by the Sounding of the Atmosphere using Broadband Emission Radiography (SABER) instrument on board NASA's Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. The two target species were used to initialize the OH airglow model, which was empirically adjusted to fit four different OH airglow emissions observed by the satellite/instrument configuration TIMED/SABER at 2.0 µm and at 1.6 µm as well as measurements by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument on board the Environmental Satellite (ENVISAT) of the transitions OH(6-2) and OH(3-1). Comparisons between the “best-fit model” obtained here and the satellite measurements suggest that deactivation of vibrationally excited OH(ν) via OH(ν≥7)+O2 might favour relaxation to OH(ν′≤5)+O2 by multi-quantum quenching. It is further indicated that the deactivation pathway to OH(ν′=ν-5)+O2 dominates. The results also provide general support of the recently proposed mechanism OH(ν)+O(3P)→OH(0≤ν′≤ν-5)+O(1D) but suggest slower rates of OH(ν=8,7,6,5)+O(3P), partly disagreeing with laboratory experiments. Additionally, deactivation to OH(ν′=ν-5)+O(1D) might be preferred. The profiles of [O(3P)] and [H] derived here are plausible between 80 and 95 km but should be regarded as an upper limit. The values of [O(3P)] obtained in this study agree with the corresponding TIMED/SABER values between 80 and 85 km but are larger from 85 to 95 km due to different relaxation assumptions of OH(ν)+O(3P). The [H] profile found here is generally larger than TIMED/SABER [H] by about 50 % from 80 to 95 km, which is primarily attributed to our faster OH(ν=8)+O2 rate.
Highlights
Atomic oxygen in its ground state (O(3P)) and atomic hydrogen (H) strongly influence the energy budget in the mesopause region (∼ 75–100 km) during the day and at night (Mlynczak and Solomo, 1993), and affect atmospheric air temperature, wind, and wave propagation (Andrews et al, 1987)
In order to minimize uncertainties between SABER and SCIAMACHY due to different measurement characteristics, we focused on the latitude range from 0 to 10◦ N, which was covered by both instruments throughout the entire year
The model results of the OH(6-2) volume emission rates (VERs) and OH(3-1) VER are a 4 km running average in order to take the averaging kernels of SCIAMACHY measurements into account
Summary
Atomic oxygen in its ground state (O(3P)) and atomic hydrogen (H) strongly influence the energy budget in the mesopause region (∼ 75–100 km) during the day and at night (Mlynczak and Solomo, 1993), and affect atmospheric air temperature, wind, and wave propagation (Andrews et al, 1987). T. Fytterer et al.: Model results of OH airglow considering four different wavelength regions role in the mesopause region due to the destruction of ozone (O3), which is accompanied by the release of a considerable amount of heat (Mlynczak and Solomon, 1993). Fytterer et al.: Model results of OH airglow considering four different wavelength regions role in the mesopause region due to the destruction of ozone (O3), which is accompanied by the release of a considerable amount of heat (Mlynczak and Solomon, 1993) This chemical reaction leads to the production of vibrationally excited hydroxyl radicals (OH(ν>0)) up to the vibrational level ν = 9, causing the formation of OH emission layers in the atmosphere (Meinel bands; Meinel, 1950)
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