Abstract
Abstract. The O2(a1Δg) emission near 1.27 µm is well-suited for remote sensing of global wind and temperature in near-space by limb-viewing observations to its bright signal and extended altitude coverage. However, vibrational–rotational emission lines of the OH dayglow produced by the hydrogen–ozone reaction (H+O3→OH•+O2) overlap the infrared atmospheric band emission (a1Δg→X3Σg) of O2. The main goal of this paper is to discuss the effect of OH emission on the wind and temperature measurements derived from the 1.27 µm O2 dayglow limb-viewing observations. The O2 dayglow and OH dayglow spectrum over the spectral region and altitude range of interest is calculated by using the line-by-line radiative transfer model and the most recent photochemical model. The method of four-point sampling of the interferogram and sample results of measurement simulations are provided for both O2 dayglow and OH dayglow. It is apparent from the simulations that the presence of OH dayglow as an interfering species decreases the wind and temperature accuracy at all altitudes, but this effect can be reduced considerably by improving OH dayglow knowledge.
Highlights
The infrared atmospheric band emission (a1 g → X3 g) of O2 observed near the wavelength of 1.27 μm has remarkable advantages in atmospheric remote sensing due to its bright signal and extended altitude coverage (Mlynczak et al, 2007)
We have simulated and discussed the effect of OH dayglow on the wind and temperature measurements derived from the 1.27 μm O2 dayglow limb-viewing observations
We first calculated the O2 and OH dayglow spectrum over the spectral region and altitude range of interest using the line-by-line radiative transfer model and the photochemical model incorporating the most recent spectroscopic parameters, rate constants and solar fluxes. They show that the OH lines RR2.5e and RR2.5f are too close to the third weak emission line of the O2 dayglow near 7823 cm−1, which will surely affect the spectral integral intensity of the O2 mission line
Summary
The infrared atmospheric band emission (a1 g → X3 g) of O2 observed near the wavelength of 1.27 μm has remarkable advantages in atmospheric remote sensing due to its bright signal and extended altitude coverage (Mlynczak et al, 2007). A similar instrument, MIMI, designed by York University, takes advantage of strong and weak emission lines for dynamics and thermodynamics measurement. Both WAMI and MIMI are imaging, fieldwidened Michelson interferometers and the same measurement technique, known as Doppler Michelson imaging interferometry, is employed successfully by the WINDII instrument on NASA’s UARS satellite (Shepherd et al, 2012). The observing strategy of using two sets of three emission lines (as shown in Fig. 1 of Ward et al, 2001) makes it a perfect approach for WAMI and MIMI to improve our knowledge of the wind and temperature of the lower thermosphere and middle atmosphere, as well as global distribution and transport of O3. To the best of our knowledge, the first consideration and discussion of the effect of OH dayglow on the temperature and wind measurements using the 1.27 μm O2 dayglow
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