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While most micrometeorological measurement techniques are only suitable for windy conditions, the Nocturnal Boundary Layer Technique can be used to measure trace gas flux during calm, clear nights as the nighttime stability enables gas emitted at the ground to accumulate. The difference between two measurements over the whole depth of this layer is believed to integrate emissions from a large area representative of, in this study, an agricultural farm. A tethersonde and infrared gas analyzer attached to a blimp carrying a bag sampling system monitored atmospheric variables for each ascent during two summer field campaigns. A mini-SODAR was installed in the field to obtain the wind flowfield. Strong accumulation was observed under low level jets suggesting that this feature acts as a good lid for trace gases. An average background vertical motion different from zero seemed to have more influence on gas propagation than did intermittent turbulence. On at least one night, a density current created by the nearby St-Lawrence River was observed to influence measurements.

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As the demand for global renewable energy grows, so does the demand for more efficient energy conversion machines and better wind resource assessment. The need to convert as much energy as possible with little cost remains the biggest challenge. In the wind energy sector, the quantity of the resource “wind” is not hard to locate, as with current ground and space based remote sensing technologies, and climate reanalysis techniques, the mapping of average wind speeds across the globe is achievable. The difficulty lies in identifying the “quality” of the wind resource. “Quality” is the measure of the time variant properties of the wind, and time scale here does not represent seasonal, monthly, or the daily variability, but rather the changes within hours, minutes, seconds, and sub‐second periods. Wind possesses a highly unpredictable, and non‐universal character, which is referred to as turbulence. These intermittencies in the wind speed create variable mechanical loads on the structure of wind turbines leading to fatigue, and ultimately failure. Identifying site specific qualities of the wind resource is very crucial in the design and selection process of the wind turbine. Physical theories explaining wind turbulence phenomena over flat terrain have been critiqued and tested by observations, and in general, have achieved reasonable success in explaining surface layer wind dynamics that can be applied universally. This universality, and the extrapolation of flat terrain theories to complex terrain applications, breaks down most of the time due to the newly recognized spatial and temporal spectrum of interaction modes, mechanically and thermodynamically, with the surrounding complex terrain. In terrain as found in New Zealand, most of the wind farm development is carried out over complex terrain, with ridge top and mountainous installations. In this study, an experimental campaign was carried out over a coastal ridge top, proposed for wind farming, to investigate mean and turbulent wind flow features significant for wind turbine selection and placement across the ridge. The steep sloped faces of the ridge, high wind speeds and its proximity to the sea made this location ideal for a benchmark investigation site. Ultra‐sonic ii anemometers, a sodar (sound detection and ranging) wind profiler, and high resolution LES (large eddy simulation) numerical modelling were all utilized separately and in an interconnected way to provide a comprehensive analysis of the wind dynamics over the ridge top. The three principal components of the investigation were: the effect of the upstream topography and the thermal circulation associated with the proximity to the sea on the observed and modelled wind shear vertical profile; the role that the near upwind terrain plays in shaping the turbulence energy spectrum and influencing the predicted spectrum, ultimately affecting isotropy in the flow field and turbulence length scales; turbulence advection from far topography, and the role that far upwind terrain plays in altering the wind turbulence in a measurement area or at a single point. Results showed that the thermal wind circulations and upstream steep topography could dictate the wind shear profile, and consequently have a large impact on wind turbine height selection and placement. The sodar proved to be a very useful tool in identifying vertical shear zones associated with effects of steep upstream terrain, vertical mixing of horizontal momentum, and thermal circulation from the local sea breeze. In complex terrain, the added multi‐directional perturbations from the underlying roughness redistribute the statistical variations (measured by variances) in the three spatial dimensions. Isotropy, based on measured variances, was attained for both sites on the ridge. Isotropy also held true for the energy spectrum via Fourier analysis of the high temporal resolution data, but not for both sites. In general, local isotropy can be attained in cases of higher wind speeds and increased terrain relief. Measured spectral ratios did not converge to the limit suggested by the local isotropy hypothesis. These results identify contradictions in assessing the turbulence isotropy in both real space (statistically through variances) and Fourier space (through power spectrum analysis), which suggests caution in deriving or interpreting turbulence information for wind turbine design and selection. iii 2D‐LES experiments showed that turbulent kinetic energy (TKE) can attain long range memory of underlying terrain, which can then react accordingly with upcoming terrain. Under the high wind speed scenarios, which are suitable for wind farming, and over relatively complex terrain, the flow retained some aspects of terrain information at least 30H (H is the terrain height) upstream and downstream of the terrain. In general, as the turbulence field travels over new terrain it tends to increase in intensity downstream of that feature. The newly modified TKE field acquires geometric features from the underlying terrain; mainly these features register as amplifications in the wave structure of the field at wavelengths comparable to the height of the underlying terrain. The 2D‐LES sensitivity experiments identified key areas of high mean wind speed and turbulence in relation to terrain effects, all of which should be taken into consideration when thinking of locating a wind farm in such areas.

Traditionally, agricultural nitrous oxide (N₂O) emission of New Zealand has been measured using chambers or lysimeters, and micrometeorological flux measurement experiments have been very few. Since micrometerological flux measurement systems have the advantage of measuring spatially integrated flux values for longer time periods compared to measurements made using chambers, development and verification of such a system was needed for New Zealand's agro-meteorological conditions. In this study, efficacy of such a combined flux gradient (FG) - eddy covariance (EC) micrometeorological flux measurement system is verified by continuously measuring N₂O fluxes from some control and mitigated agricultural plots of New Zealand. The control fields had natural N₂O emission, whereas, the mitigated plots were treated with chemicals to reduce N₂O emission. In this combined FG-EC method, the turbulent eddy diffusivities were estimated using the Monin-Obukhov (M-O) similarity theory based parameterization (where diffusion velocity `dhp' was used) and a thermal approach (where eddy diffusivity `kht' was used) from the EC measurements. These transfer coefficients (kht and dhp) along with the measured N₂O concentration differences were then fitted to the traditional FG equation to compute final flux values. As the primary objective of this study, measured fluxes from two different seasons and from two approaches were compared for consistency and then verified against published results. Under this wider objective of verification of the FG-EC micrometeorological method of N₂O flux estimation, this research thesis addresses three key issues: (i) assessment of error propagation in the measured flux through the eddy diffusivity - to understand the random error dynamics of the system and to estimate precision of the overall method, (ii) quantification and separation of N₂O source area emission rates from adjacent plots - to identify the contribution of an individual plot to the measured flux when multi-plot fluxes were measured from sources with different biogenic characters, and (iii) quantification of the effect of animal grazing and mitigation on the measured flux and actual emission rate of N₂O - to assess robustness of the FG-EC micrometeorological system. As a fourth objective of this study, (iv) new scaling properties of a turbulence surface layer model of a convective atmosphere is investigated as an alternative to the standard M-O similarity theory, as significant questioning of the M-O theory has been reported in some recent publications. Results from the verification experiment showed that the daily measured flux values obtained from this combined micrometeorlogical system for control plots varied between 0-191.9 and 0-491.8 gN₂O-N.ha⁻¹.day⁻¹ for autumn and spring experiments, respectively, for the parameterization method. Similarly, the daily mean flux values were found to be 10.9 ± 0.98 and 11.7 ± 0.57 gN₂O-N.ha⁻¹.day⁻¹ for the autumn and spring seasons, respectively. All these values were found to be of the same order of previously reported values in the literature and found to verifying that this FG-EC system works well under a range of meteorological conditions within a defined error range. Therefore, when the propagated random error was computed in the final flux value using kht and dhp, the mean relative error in kht was found to be higher than the mean relative error in dhp, irrespective of stability. From a Monte-Carlo type simulation of the random error, it was found that the maximum error can be up to 80% for kht irrespective of stability, and 49% and 35% for dhp respectively for stable (1/L ≥ 0, where L is Obukhov length) and unstable (1/L < 0) atmosphere. Errors in the concentration differences were estimated based on the minimum resolvable estimates from the gas analyzer and the associated random errors were found to be 6% and 8% for unstable and stable conditions. Finally, the total mean random error in the N2Oflux values was found to be approximately of the order of 9% and 12% for the parameterization method for unstable and stable conditions, respectively, and 16.5% for the thermal method, irrespective of stability. Objective (ii) of this research was addressed by developing a `footprint fraction' based inverse footprint method. Results of the footprint analysis method were assessed, first, by comparing footprint fractions obtained from both an analytical footprint model and a `forward' simulation of a backward Lagrangian stochastic (bLs) model; and second, by comparing the source area emission rates of a control plot obtained from the footprint analysis method and from the `backward' simulation of the bLs model. It was observed that the analytical footprint fractions were realistic as they compared well with the values obtain from the bLs model. The actual emission rates were found to be on average 2.1% higher than the measured flux values for the control plots. On average 4.3% of the measured fluxes were found to be contributed by source areas outside of the field domain. Again, the proposed footprint method of emission rate estimation was found to work well under a wider range of atmospheric stability, as the inverse footprint model and bLs model based emission rates were found to correlate well (0.70 and 0.61 for autumn and spring, respectively) with a 99% statistical significance. Similarly when the effect of grazing on the N₂O fluxes was considered, a 90% enhancement in the flux values was observed after grazing, followed by a decreasing trend in fluxes. However, contrary to existing knowledge of mitigation of N₂O flux by an inhibitor, this study found no statistically significant effect of mitigation in the pastoral emission of N₂O. Error accumulation, lesser soil N₂O production potential and/or inefficiency of the FG-EC method was conjectured to be reason/s for such discrepancy and some alternative convective boundary layer turbulence scaling was tested. Separate field measurement data, including the vertical profile measurements of the convective boundary layer and sonic anemometer measurements within the surface layer were used for this purpose. The spectral analysis of the vertical wind component, temperature and heat flux revealed that this new model of the convective boundary layer, which explains atmospheric boundary layer turbulence in terms of some nonlocal parameters, is more suitable than the traditional Monin-Obukhov similarity theory based model of atmospheric turbulence where the atmospheric flow properties are local. Therefore, it can be concluded that this new model of turbulence might provide the framework for a newer model of flux estimation in future. Overall, the FG-EC model of N₂O flux estimation method seems to work well within a certain error range. However, more field applications of this FG-EC method are needed for different agro-meteorological conditions of New Zealand before this method is accepted as a standard method of flux estimation, particularly, inefficiency in detecting the effect of mitigation should be tested. Development of an alternative flux gradient model which includes nonlocal atmospheric surface parameters might also be considered as a future research objective.

This thesis describes the preparation of surface-attached monolayer tethers from electroreduction of aryldiazonium ions using a protection-deprotection strategy. Monolayers of ethynylphenyl, carboxyphenyl, aminophenyl and aminomethylphenyl were prepared. Glassy carbon (GC) and pyrolysed photoresist film (PPF) surfaces were modified electrochemically and characterised by redox probe voltammetry. The monolayer tethers were coupled with electro-active ferrocenyl (Fc) and nitrophenyl (NP) groups for the indirect electrochemical estimation of the surface concentration. Film thickness measurement was carried out using an atomic force microscopy (AFM) depth profiling technique. The surface concentration and film thickness measurement results were consistent with the formation of monolayer films after removal of the protecting groups. Preparation of mixed monolayers was studied using three different modification strategies: i) grafting from a solution containing two different protected aryldiazonium ions, ii) sequential grafting of two different protected aryldiazonium ions, and iii) grafting of protected aryldiazonium ions followed by removal of the protecting group and reaction of an amine or carboxylic acid derivative directly with the GC surface. The composition of the mixed layer prepared using the first method is difficult to control, whereas the possibility of multilayer formation cannot be discounted using the second method. Multilayer formation is unlikely using the third method. The electrocatalysis of oxygen reduction at mixed monolayer films was investigated briefly. The origin of the two reduction peaks frequently observed for electroreduction of aryldiazonium ions at carbon surfaces was studied. Electroreduction was carried out at GC and HOPG surfaces. The reduction peak at the more positive potential is surface sensitive, while the peak at the more negative potential is not. However, both reduction peaks lead to deposition of films and it is tentatively proposed that the more positive peak corresponds to reduction at a ‘clean’ GC electrode, and the more negative peak corresponds to reduction at the already grafted layer.