Abstract
The O2(a1Δg) emission near 1.27 μm provides an important means to remotely sense the thermal characteristics, dynamical features, and compositional structures of the upper atmosphere because of its photochemistry and spectroscopic properties. In this work, an emission–absorption transfer model for limb measurements was developed to calculate the radiation and scattering spectral brightness by means of a line-by-line approach. The nonlocal thermal equilibrium (non-LTE) model was taken into account for accurate calculation of the O2(a1Δg) emission by incorporating the latest rate constants and spectral parameters. The spherical adding and doubling methods were used in the multiple scattering model. Representative emission and absorption line shapes of the O 2 ( a 1 Δ g , υ ′ = 0 ) → O 2 ( X Σ g 3 , υ ″ = 0 ) band and their spectral behavior varying with altitude were examined. The effects of solar zenith angle, surface albedo, and aerosol loading on the line shapes were also studied. This paper emphasizes the advantage of using infrared atmospheric band for remote sensing of the atmosphere from 20 up to 120 km, a significant region where the strongest coupling between the lower and upper atmosphere occurs.
Highlights
Measurements of radiation of electronically excited molecular oxygen in the atmospheric band O2 ( b1Σg, υ = 0 → X3Σg, υ = 0 ) at 762 nm and in the infrared atmospheric band O2 ( a1∆g, υ = 0 → X3Σg, υ = 0 ) at 1.27 μm provide fundamental probes into energy transfer, compositional structures, and thermodynamic and dynamic features of the upper stratosphere, mesosphere, and lower thermosphere
We have presented simulations of the radiative transfer characteristics of the O2 infrared atmospheric band in limb-viewing geometry
Both the nonlocal thermal equilibrium (non-local thermodynamic equilibrium (LTE)) effect and multiple scattering were taken into account for developing the radiative transfer model
Summary
Wu et al reported the application of O2(a1∆g) dayglow for wind observation with a Doppler Asymmetric Spatial Heterodyne (DASH) type instrument from a limb-viewing satellite by measuring Doppler shifts of the emission line O19P18, which were detectable due to their weak self-absorption, bright radiation intensity, and large spectral separation range [7]. Dobler et al discussed the feasibility of determining surface pressure by measuring atmospheric O2 near the 1.27 μm band for determination of CO2 mixing ratio columns with a laser absorption spectrometer [10]. Sharp et al reported the impact of ambient O2(a1∆g) on O2 column remote sensing with satellite-based laser using absorption lines in the 1.27 μm band [11].
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