Impact of ambient O₂(a¹Δ_g) on satellite-based laser remote sensing of O₂columns using absorption lines in the 1.27 µm region

Abstract

Determination of CO 2 mixing ratio columns from space using Laser Absorption Spectroscopy (LAS) requires simultaneous measurements of CO 2 number density columns and knowledge of the dry atmospheric surface pressure. One approach to determining the surface pressure is to make an LAS column measurement of O 2 number density in the 7857.3-7921.7 cm À1 (1.27 μm) region of the O 2 ( 1 Δ) state. A complicating factor in the LAS O 2 measurement is the presence of a permanent but spatially variable natural source of airglow from the O 2 ( 1 Δ) state. In addition, the laser radiation can induce stimulated emission from the ambient O 2 ( 1 Δ) state and also cause stimulated absorption and emission from the ground state O 2 molecules as the laser beam passes through the atmosphere. Finally, the upwelling surface-reflected solar radiation is an additional source of background radiation. The effects of these additional radiation sources on the LAS measurement of O 2 are examined. The surface-reflected solar radiation produces the largest background at 3 orders of magnitude more intense than the laser backscatter signal, while the airglow is of the same order of magnitude as the laser backscatter. The stimulated emission from ambient O 2 (a 1 Δ g ) is found to be about the same order of magnitude as the laser radiation. These effects are evaluated under noon, twilight, and midnight conditions at midlatitudes, the equator, and the pole. The stimulated emission is in the same direction and in phase with the laser signal, its contamination of the LAS O 2 measurement prevents a full sunlight determination of surface pressure.

Photochemical modeling of molecular and atomic oxygen based on multiple <i>in-situ</i> emissions measured during the Energy Transfer in the Oxygen Nightglow rocket campaign

“…A photochemical model taking O 2 (b, a, X) states and O( 1 D, 3 P ) states into account was developed by Mlynczak et al (1993) with the use of the basic daytime O 2 (a) kinetic model employed by Thomas (1990). The model of Mlynczak et al (1993) was extended by Sharp et al (2014) by including the three-body recombination reaction producing O 2 (a) during night time, see the R a1.1−2 reactions provided in Table 3. The model of Sharp et al (2014) also included processes related to the laser excitation, but these processes are not relevant for the present study and are excluded.…”

“…The model of Mlynczak et al (1993) was extended by Sharp et al (2014) by including the three-body recombination reaction producing O 2 (a) during night time, see the R a1.1−2 reactions provided in Table 3. The model of Sharp et al (2014) also included processes related to the laser excitation, but these processes are not relevant for the present study and are excluded.…”

“…All other processes of the model proposed by Sharp et al (2014) are shown in Table 3. The modified kinetic model with these processes is hereafter referred to as the M-model in short according to the surname of the first author in Mlynczak et al (1993).…”

“…The following processes were adopted in the MAC model from the M-model of Mlynczak et al (1993) and Sharp et al (2014), see Table 3 in Section 3.2.1. These processes are related to:…”

The Radiative Transfer Characteristics of the O2 Infrared Atmospheric Band in Limb-Viewing Geometry

“…The absorption and emission spectral features also interact with each other in atmospheric remote sensing. Sharp et al reported the impact of ambient O 2 (a 1 ∆ g ) on O 2 column remote sensing with satellite-based laser using absorption lines in the 1.27 µm band [11]. Bertaux et al evaluated the contribution of O 2 (a 1 ∆ g ) airglow to the retrieval accuracy of CO 2 mixing ratio columns in the MicroCarb optical concept [12].…”