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Title: Active and passive remote sensing of the troposphere : broadband lidar measurements of NO2 and studies of anomalous atmospheric absorption
Author: Hill, C.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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Ground-based, passive remote sensing techniques are well established and routinely used for measuring the concentrations of important trace constituents in the troposphere. DOAS (differential optical absorption spectroscopy) is a sensitive technique for measuring low concentrations of atmospheric species. However, such measurements generally represent averages over long path-lengths, which may be poorly defined, and little spatially-resolved information is attainable. Active remote sensing by lidar (light detection and ranging) enables vertical profiles of constituents to be obtained using the DIAL (differential absorption lidar) technique, but this approach is susceptible to large errors due to wavelength-dependent aerosol scattering and interfering absorption from other species. DOAS and DIAL can be combined by the use of a broadband (˜10 nm) pulsed laser light source coupled with a range-gated, spectrally-resolving CCD detector. The broadband lidar has already been demonstrated in its application to the measurement of water vapour profiles; this thesis assesses the feasibility of measuring NO2 profiles by the technique and reports tropospheric NO2 column amounts obtained under polluted conditions. While NO2 was detectable, no vertical profile information was attainable at the current signal-to-noise levels. Modifications to the instrument made since 1996 are reported, with recommendations for future improvements to enable high-resolution altitude profiles of NO2 to be retrieved. The application of the broadband lidar instrument to the measurement of boundary layer height is described, with emphasis on its deployment during the PUMA (Pollution of the Urban Midlands Atmosphere) field campaign during January-February 2000.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available