Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [150]-166).

Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 2001. / "Figures, tables and the appendices appear in the volume II". Bibliography: leaves 130-152.

Trace gases can have a significant impact on the Earth's climate, and the analysis of changes in these gases and an understanding of how much of these changes are a result of human activity is important for understanding global climate change. Methane (CH4) is the second only to CO2 in radiative forcing over the last 200 years, and its concentration in the atmosphere has more than doubled since 1750. Sources and sinks of CH4 have characteristic isotopic effects, which shift the relative concentration of the methane isotopologues. Spectroscopic techniques for of analysis the isotopic composition of methane have been evolving since the early 1990's, and promise real-time, in-situ measurements that would provide unprecedented information on the methane atmospheric cycle. Here we present our development and results of a new optical spectroscopic isotope ratio instrument using cavity ringdown spectroscopy in the near IR region using the ν2+2ν3 overtone band. This region has limited interference from other molecules, and an advantageous juxtaposition of a 13CH4 triplet, and a single 12CH4 peak, allowing near-simultaneous measurement of both isotopologues. We present the results of two datasets showing high linearity over a wide range of isotope ratios, which achieved a precision of ±4 /. We present analysis of the data and consider the effects of temperature and molecular interference.

No description available.

Two approaches, one using an atmospheric diffusion model and the other an atmospheric tracer, were used to predict the source strength of trace gases from observations of the downwind concentration field. Both approaches do not disturb the prevailing environmental and physical conditions nor the existing biogenic processes. An analytical solution to the advection-diffusion equation was used to back-calculate the source strength from the downwind concentration measurements of (i) single and multipoint (4 and 16 points) trace gas (sulphur hexafluoride (SF6) and methane (CH4)) release experiments conducted over microplots over an open field, and (ii) single point source SF6 release experiments conducted over a forested terrain. Best predictions of the source strength (to within +/-20%) were obtained from concentration observations made along the centreline of the diffusing plumes with the predictions improving when observations at the mean plume height were used. The diffusion model was then used to compute footprint estimates for neutral and unstable conditions, for tower and aircraft based observation platforms above the forest. They showed spatially constrained footprints in the surface layer, due to effective vertical coupling, so that observations from towers and low flying aircraft must be expected to be very site specific, and scaling up to larger areas will have to be done with careful consideration of surface mosaics. Above-canopy sampling of trace gases to determine volatile organic compound emissions were then interpreted in terms of footprint considerations. This was accomplished by defining the upwind canopy areas effectively sampled under the given wind and stability conditions. The analysis demonstrated, for example, that the variability observed in measured isoprene fluxes could be accounted for by varying numbers of randomly distributed clumps of emitter species within a varying footprint. It suggested that heterogeneity of the forest canopy, in ter / Sulphur hexafluoride was also used as an atmospheric tracer in order to estimate CH4 emissions from manure slurry and cattle housed in barns and feedlots. (Abstract shortened by UMI.)

Spectroscopic measurements in the infrared have proven to be a valuable source of information about the Jovian atmosphere. However, numerous questions remain, many of which will be addressed by the Galileo μission, due to arrive at Jupiter in December, 1995. One of the instruments on Galileo is the Near-Infrared Mapping Spectrometer (NIMS), which will measure temperature structure, cheμical composition, and cloud properties. The objective of the work described in this thesis was to investigate the transmittance properties of the Jovian atmosphere and, in particular, to obtain transmittance functions of CH₄ for future use in the planning and interpretation of NIMS measurements. This thesis begins with a review of our current understanding of the Jovian atmosphere (Chapter 1), and a description of the Galileo μission and the design and objectives of NIMS (Chapter 2). It is then shown (Chapter 3) that absorption bands of CH₄ doμinate the nearinfrared spectrum of Jupiter, but that line data for CH₄ are currently inadequate over much of the NIMS spectral range (0.7-5.2 /μi). For the purposes of NIMS, which has a low resolution of 0.25 /μi, the spectrum of CH₄ can be characterised using band models of transmittance as a function of temperature, pressure, and abundance. The theory of band modelling is presented, and previous band-modelling studies of CH₄ are reviewed and are also shown to be inadequate for NIMS (Chapter 4). An experimental investigation was therefore undertaken to record CH₄ spectra under Jovian conditions of low temperature, large abundance, and H₂-broadening. The experimental resources used to obtain these spectra are described (Chapter 5), the generation of the transmittance spectra is discussed, and their quality is assessed (Chapter 6). The range of frequencies and laboratory conditions covered by these spectra (listed in Appendix A) makes them one of the most comprehensive data sets of this kind yet published. These spectra were subsequently used to derive transmittance functions for CH₄ (Chapter 7). A variety of models were fitted to the self-broadened CH₄ spectra, and the Goody and Malkmus random band models, using the Voigt lineshape, are shown to provide the best fits. These two models were then fitted to the combined set of self- and H₂-broadened CH₄ spectra. The parameters fitted with the Goody-Voigt model are included in this thesis (Appendices B and C). Finally, the application of these new band model fits to the problem of Jovian remote sounding is addressed (Chapter 8). This includes an assessment of the reliability of extrapolation to Jovian conditions, a calculation of the level in the Jovian atmosphere that will be sounded by observations of CH₄ absorption, and a calculation of how the uncertainties in the fitted band model will affect the retrieval of atmospheric parameters from NIMS spectra. This thesis concludes with a detailed summary, and with suggestions for future investigations which will help to maximise the return of information from NIMS.

Thesis (M. Sc)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 85-90). Also available via the World Wide Web.

A soil climate parameterization is designed for peatland environments in the Canadian Land Surface Scheme (CLASS). Three wetland soil classes account for the variation in the hydraulic characteristics of organic soils. Saturated hydraulic conductivity varies from a median of 1.0 x 10-7 m/s in deeply humidified sapric peat to 2.8 x 10-4 m/s in relatively undecomposed fibric peat. Average pore volume fraction ranges from 0.83 to 0.93. Parameters are derived for the soil moisture characteristic curves of fibric, hemic and sapric peat, using the Campbell (1974) equation employed in CLASS, and the van Genuchten (1980) formulation. Validation of modelled water table depth and peat temperature is performed for a fen in northern Quebec and a bog in north-central Minnesota. The new parameterization results in more realistic simulation than the previous version of CLASS, which was constrained to using mineral soil properties to approximate those of organic soils. / Two approaches are used to model methane emissions from northern peatlands using the new soil climate parameterization in CLASS. In the first module, the multiple regression equation of Dise et al. (1993) is used to simulate daily methane emissions from water table depth and peat temperature. In the process-based module, methane flux is divided into its component parts: plant transport, diffusion and ebullition. Each of these transport mechanisms is determined by methane concentrations, which are calculated from a series of processes related to peat temperature, water table level and rooting depth. The daily methane emissions predicted by the two models are similar and correlate reasonably with observations from a bog in north-central Minnesota.

No description available.

No description available.