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Bridging the Gap in Radiative Transfer Modelling using O2 A-Band Emissions in the Mesosphere

Date

2019-07-12

Journal Title

Journal ISSN

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Publisher

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Type

Thesis

Degree Level

Masters

Abstract

One of the brightest emission features in the spectral radiance of the atmosphere during the daytime is due to oxygen (O2) emission. The A-band photochemical emission is found between 758 and 770 nm and is strongly dependent on the temperature in the mesosphere and lower thermosphere (MLT). It begins contributing above 40 km altitude near the stratopause, and is visibly dominant above 60 km. Typically, the study of photochemical emissions at this altitude does not require consideration of extensive scattering processes due to low atmospheric density. As a result, atmospheric models are historically divided between those capable of simulating absorption and multiple scattering processes below the stratopause, and those which can model simple radiative transfer and photochemical emission in the MLT. The MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) mission is designed to study gravity waves in the MLT and their effect on the structure of polar mesospheric clouds (PMCs). Because of the desire to observe aerosols in the upper atmosphere, an atmospheric model capable of accurately simulating both scattering and emission is required. The original SASKTRAN radiative transfer model was designed in support of the OSIRIS (Optical Spectrograph and Infra-Red Imaging System) instrument on the Odin satellite, and is only capable of modelling absorption and multiple scattering processes, with no inclusion of photochemical emissions. The purpose of this thesis is to design a photochemical emission model of O2 in the A-band for integration into the original SASKTRAN framework to create an integrated model that handles emission and multiple scattering in a consistent fashion. The upgraded atmospheric model is capable of simulating radiance propagation through the MLT in the presence of PMCs, including absorption, scattering, and photochemical emission. As a result, radiance can be accurately simulated through the entire atmosphere, bridging the gap in atmospheric models that were previously divided between the lower and upper atmosphere. While the primary motivation for this work is in support of the MATS project, the newly designed model has wider applications in any area of study that requires a comprehensive model of atmospheric processes.

Description

Keywords

Photochemical emissions, atmospheric physics, airglow, polar mesospheric clouds, limb viewing, atmospheric modelling

Citation

Degree

Master of Science (M.Sc.)

Department

Physics and Engineering Physics

Program

Physics

Advisor

Degenstein, Doug
Bourassa, Adam

Committee

Hussey, Glen;Chang, Gap Soo;Evitts, Richard;Dick, Rainer

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DOI

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