This thesis describes the comparison of time-lapse field observations of suncups on alpine snow with numerical simulations. The simulations consist of solutions to a nonlinear partial differential equation which exhibits spontaneous pattern formation from a low amplitude, random initial surface. Both the field observations and the numerical solutions are found to saturate at a characteristic height and fluctuate chaotically with time. The timescale of these fluctuations is found to be instrumental in determining the full set of parameters for the numerical model such that it mimics the nonlinear dynamics of suncups. These parameters in turn are related to the change in albedo of the snow surface caused by the presence of suncups. This suggests the more general importance of dynamical behaviour in gaining an understanding of pattern formation phenomena.

Precipitation phase is fundamental to a catchment’s hydrological response to precipitation events in cold regions and is especially variable over time and space in complex topography. Phase is controlled by the microphysics of the falling hydrometeor, but microphysical calculations require detailed atmospheric information that is often unavailable and lacking from hydrological analyses. In hydrology, there have been many methods developed to estimate phase, but most are regionally calibrated and many depend on air temperature (Ta) and use daily time steps. Phase is not only related to Ta, but to other meteorological variables such as humidity. In addition, precipitation events are dynamic, adding uncertainties to the use of daily indices to estimate phase. To better predict precipitation phase with respect to meteorological conditions, the combined mass and energy balance of a falling hydrometeor was calculated and used to develop a model to estimate precipitation phase. Precipitation phase and meteorological data were observed at multiple elevations in a small Canadian Rockies catchment, Marmot Creek Research Basin, at 15-minute intervals over several years to develop and test the model. The mass and energy balance model was compared to other methods over varying time scales, seasons, elevations and topographic exposures. The results indicate that the psychrometric energy balance model performs much better than Ta methods and that this improvement increases as the calculation time interval decreases. The uncertainty that differing phase methods introduce to hydrological process estimation was assessed with the Cold Regions Hydrological Model (CRHM). The rainfall/total precipitation ratio, runoff, discharge and snowpack accumulation were calculated using a single and a double Ta threshold method and the proposed physically based mass and energy balance model. Intercomparison of the hydrological responses of the methods highlighted differences between Ta based and psychrometric approaches. Uncertainty of hydrological processes, as established by simulating a wide range of Ta methods, reached up to 20% for rain ratio, 1.5 mm for mean daily runoff, 0.4 mm for mean daily discharge and 160 mm of peak snow water equivalent. The range of Ta methods showed that snowcover duration, snow free date and peak discharge date could vary by up to 36, 26 and 10 days respectively. The greatest hydrological uncertainty due to precipitation phase methods was found at sub-alpine and sub-arctic headwater basins and the least uncertainty was found at a small prairie basin.

A wide area assessment of forecast changes in wintertime synoptic conditions over western North America is combined with a meso-scale alpine hydrometeorology model to evaluate the joint impact(s) of forecast climate change on snowpack conditions in an alpine watershed in the southern Canadian Rockies. The synoptic analysis was used to generate long-term climate time series scenarios using the CCCma CGCM1. An alpine hydrometerology model is used to predict changes in wintertime precipitation at the watershed scale. A mass balance snow model is utilized to predict the overall snow accumulation throughout a watershed. A vapour transfer model has been incorporated in the snow model to estimate snow volumes more accurately. The synoptic analysis and GCM output forecasts a modest increase in both winter precipitation and temperatures in the study area, resulting in a decline of winter snow accumulations, and hence an expected decline in spring runoff. / ix, 87 leaves : ill. ; 28 cm.

Forest disturbances significantly affect snowmelt dominated watersheds. Given that snowmelt from mountain regions provides up to 80% of the annual stream ow in the North American west, disturbances in these watersheds will impact water availability for downstream users. This study used eld data from stand-scale studies to represent forest disturbances in a hydrological model in order to quantify the potential snow hydrology response to varying spatial extent of disturbance. The sensitivity of snow accumulation and ablation response increased with disturbance severity and extent of disturbance. Results may provide water resource management with a greater understanding of the potential impact on post-disturbance snowmelt runo ff. / xii, 135 leaves : ill. ; 29 cm

Electric mobility scooters are increasing in popularity and are used extensively by individuals with mobility impairments to conduct activities of daily living. Scientific literature on the safety and efficacy of scooters in winter conditions is sparse and the current technical standards for scooters do not mandate testing in these conditions. This study paves the way for more rigorous standard testing by: 1) Describing a novel, motion-capture based method to quantify the tractive performance of scooters; 2) Describing methods to create a wide variety of simulated winter conditions; 3) Presenting pilot-test results of a scooter driven in these winter conditions. The outcomes of this study are significant because it is the first study to evaluate the performance of a scooter in winter conditions. Furthermore, it constitutes the first phase of a broader initiative to develop a rigorous, new winter test method for scooters and drive improvements in safety, performance and design.

Climate change has coincided with expansion of deciduous shrub species in the Arctic. Increased deciduous vegetation in the tundra could have profound implications on regional climate, carbon balance, and biogeochemical cycling of nutrients. Winter biological processes may be a mechanism explaining shrub expansion in the Arctic. Tall shrubs accumulate relatively deep snowcover, raising winter soil temperature minima, enhancing microbial activity and promoting nitrogen mobilization that may then be taken up by shrubs. However, it has yet to be determined if shrubs can acquire winter-mobilized nitrogen, and if so, whether they acquire it early in the spring, or over the growing season. The purpose of this study was to test if increased snow alone or the combination of vegetation-type and snow depth affect nitrogen cycling and plant uptake. To test this, inorganic 15nitrogen tracer was added to control and experimentally deepened snow plots (using snowfences) in low birch hummock tundra, and to tall birch-dominated plots near Daring Lake, N.W.T. in the Canadian low Arctic. The first study (Chapter 2) characterizes soil 15nitrogen cycling over a single winter to investigate if experimentally deepened snow in low birch hummock ecosystems enhances nutrient availability to plants in the early spring. In addition, 15nitrogen cycling in low birch hummock and tall birch ecosystems were compared to characterize the combined impacts of vegetation-type and snow depth on nutrient availability to plants by early spring. The second study (Chapter 3) investigated the longer term fate of added 15nitrogen to determine if 15nitrogen acquisition and allocation differs among plant species over a two year period. Together, the results indicate that nitrogen cycling in the low birch hummock tundra was not significantly affected by deeper snow over short (after one winter) or longer terms (two years). By contrast, nitrogen availability in early spring, and birch shrub 15nitrogen uptake after two years were enhanced in the tall birch as compared to the low birch hummock ecosystem. These results suggest that the combination of vegetation-type and snow depth effects in the tall birch ecosystem could be a mechanism contributing to tundra to shrubland transitions across the Arctic. / Thesis (Master, Biology) -- Queen's University, 2009-09-18 13:36:29.401

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