Measuring tropospheric water vapour and surface emissivity using far-infrared radiances
- Resource Type
- Electronic Thesis or Dissertation
- Authors
- Warwick, Laura Rachel
- Source
- Subject
- Language
- English
This thesis describes two strands of work relating to the gathering of far-infrared (wavenumbers 10-667 cm−1 wavelengths 15-1000µm) radiance measurements, exploring the capabilities of the instruments involved and examining the data generated in the context of the relevant models. The first strand of the thesis explores the role of atmospheric water vapour which absorbs strongly in the far-infrared. The work described makes use of spectrally resolved far-infrared radiance measurements taken during the PIKNMIX-F airborne field campaign. On this field campaign co-incident upwelling mid- and far-infrared spectra were recorded in clear sky and overflying cirrus. The clear sky spectra from one flight are used to investigate the sensitivity of the far-infrared to the atmospheric water profile. Forward modelling is used to explore the changes to the expected radiance caused by changes in the surface properties and water vapour spectroscopy. Retrievals of water vapour and temperature profiles are also carried out. These show that the far-infrared radiance measurements contain more information about the atmospheric water vapour profile than the co-incident mid-infrared radiance measurements for this set of instruments. The second strand of the thesis describes the new FINESSE instrument and its first measurements of far-infrared surface emissivity. FINESSE combines a commercial Fourier transform spectrometer with a spectral range of 400-1600 cm−1 and a custom pointing and calibration system. The main purpose of FINESSE is to make in-situ measurements of surface emissivity extending into the far-infrared. As part of the development of FINESSE, a simulator is produced that allows for the emissivity retrieval to be tested under different environmental conditions. This thesis describes the first measurements of emissivity made by FINESSE. The emissivity of deionised water is retrieved using radiance measurements made from the rooftop of Imperial College London during summer and winter conditions. The measurements compare favourably to theoretical calculations and previous mid-infrared measurements.