Low-temperature high precision measurements of line mixing and collisional induced absorption in the oxygen A-band

Adkins, Erin M.

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https://hdl.handle.net/2142/100770 Copy

Description

Title

Low-temperature high precision measurements of line mixing and collisional induced absorption in the oxygen A-band

Author(s)

Adkins, Erin M.

Contributor(s)

• Hodges, Joseph T.
• Long, David A.
• Ghysels, Mélanie

Issue Date

2018-06-18

Keyword(s)

Linelists, Lineshapes, Collisions

Abstract

Because of the constant mixing ratio of molecular oxygen (O2) within the Earth’s atmosphere, the O2 A-band is commonly used in satellite and remote sensing measurements as a measure of the airmass. A recent collaborative effort has produced a self-consistent integrated spectroscopic model for the O2 A-Band that simultaneously accounts for highorder line-shapes, line mixing (LM), and collisional induced absorption (CIA).a This model has improved OCO-2 mission retrievals of dry air CO2, however, limitations in existing spectroscopic models still lead to airmass dependent biases. Currently, model development is limited by a lack of high resolution experimental data at low temperatures and in the Rbranch. To address this, measurements of the entire O2 A-band were recently made with a variable-temperature cavity ringdown spectrometer (CRDS) over a range of temperatures, pressures, and molar fractions. Because of the limited dynamic range of the CRDS system, at high molar fractions of O2 saturation can occur at the line cores of strong transitions. Therefore, a range of molar fraction O2 samples were employed. Low mole fraction data, which was unaffected by saturation provided information on the temperature dependence of high-order line-shape parameters. Conversely, high molar fraction data provided information on LM and CIA effects that dominate absorption in the troughs between saturated transitions. By combining this high-resolution experimental data, that covers both the entire O2 A-Band as well as a range of temperatures, with existing datasets, these results aim to improve on LM and CIA models for the next iteration of the global O2 A-Band model.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/100770

DOI

10.15278/isms.2018.MI05

Copyright and License Information

Copyright 2018 Erin M. Adkins

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