A large portion of the freshwater in western Canada originates as snowpack from the northern Rocky Mountains. The temperature and precipitation in these areas controls the amount of snow accumulated and stored throughout the winter, and the amount and timing of melt that occurs during the spring freshet. Therefore, a better understanding of past and future changes to the extent of snowpack and timing of melt can modify the timing of peak river flow on a continental scale. Trends in temperature, precipitation, snow accumulation, and snowmelt are examined using the Mann-Kendall non-parametric test on a high resolution gridded climate dataset over western Canada for the period 1950-2010. In addition, projected changes in temperature, precipitation, snow water equivalent, and snowmelt are examined through comparison of the current (1971-2000) and future (2041-2070) time periods incorporating several regional climate models. The temporal and spatial analyses of these key hydroclimatic variables indicate that changes vary greatly over space and time. Results reveal that while both maximum and minimum temperature have increased in the past 60 years, minimum temperature has increased more than maximum temperature and is likely to continue doing so in the future. This trend is particularly evident during the colder months of the year, and at higher elevations, contributing to earlier spring melt. Between 1950 and 2010, precipitation has decreased throughout the colder months of the year and increased in the warmer months, particularly in the northern half of the study area. Future projections show increased precipitation, specifically in the north. Throughout the historical period snow accumulation has experienced decreases across the study area and through all months of the year, except for increases at high elevations. In the coldest months of the year snow accumulation is projected to increase in high elevation and northern areas while decreasing across the rest of study area in the future. Snowmelt results indicate slight increases in mid-winter melt events and an earlier onset of the spring freshet; this change is expected to continue into the future period. This study provides a summary of detected trends and potential future changes in key hydroclimatic variables across western Canada with regard to the effects these changes can have on the spring freshet and streamflow, and thus water resources, throughout the study area. / Graduate / 0368

As the need to understand climate induced changes increases, so too does the need to understand the long-term spatial-temporal characteristics of snow cover and snow water equivalence (SWE). Snow cover and SWE are useful indicators of climate change. In this research, we combine methods from spatial statistics, geographic information systems (GIS), time-series analysis, ecosystems classification, cluster analysis, and remote sensing, to provide a unique perspective on the spatial-temporal interactions of SWE. We show that within the Canadian Prairies, extreme SWE are becoming more spatially constrained, and may cause some regions to be more prone to flooding. As well, we find that the temporal characteristics of SWE are not captured by current ecological management units, highlighting the need for Canadian ecological management units that consider winter conditions. We then address this need by developing methods designed to generate geographically distinct SWE regimes. These regimes are used to partition the landscape into winter-based management units, and compared with conventional summer based units. We find that regional variations in the ability of current ecological units to capture SWE characteristics exist, and suggest that SWE regimes generated as a result of this analysis should be used as guidelines for developing winter-based management units in conjunction with current ecological stratifications.

A large portion of the freshwater in western Canada originates as snowpack from the northern Rocky Mountains. The temperature and precipitation in these areas controls the amount of snow accumulated and stored throughout the winter, and the amount and timing of melt that occurs during the spring freshet. Therefore, a better understanding of past and future changes to the extent of snowpack and timing of melt can modify the timing of peak river flow on a continental scale. Trends in temperature, precipitation, snow accumulation, and snowmelt are examined using the Mann-Kendall non-parametric test on a high resolution gridded climate dataset over western Canada for the period 1950-2010. In addition, projected changes in temperature, precipitation, snow water equivalent, and snowmelt are examined through comparison of the current (1971-2000) and future (2041-2070) time periods incorporating several regional climate models. The temporal and spatial analyses of these key hydroclimatic variables indicate that changes vary greatly over space and time. Results reveal that while both maximum and minimum temperature have increased in the past 60 years, minimum temperature has increased more than maximum temperature and is likely to continue doing so in the future. This trend is particularly evident during the colder months of the year, and at higher elevations, contributing to earlier spring melt. Between 1950 and 2010, precipitation has decreased throughout the colder months of the year and increased in the warmer months, particularly in the northern half of the study area. Future projections show increased precipitation, specifically in the north. Throughout the historical period snow accumulation has experienced decreases across the study area and through all months of the year, except for increases at high elevations. In the coldest months of the year snow accumulation is projected to increase in high elevation and northern areas while decreasing across the rest of study area in the future. Snowmelt results indicate slight increases in mid-winter melt events and an earlier onset of the spring freshet; this change is expected to continue into the future period. This study provides a summary of detected trends and potential future changes in key hydroclimatic variables across western Canada with regard to the effects these changes can have on the spring freshet and streamflow, and thus water resources, throughout the study area. / Graduate / 0368

No description available.

This study aims to present and evaluate a new method for measuring the distribution of snow within built-up environments by differencing elevations collected by an Airborne Laser Scanner (ALS) before, and during peak snow accumulation. Few efforts have been made to study the distribution of snow within built-up environments due to the false assumption that high-intensity rainfall is the main contributor to peak yearly runoff rates. Traditional techniques for measuring snow are often difficult to replicate in built-up environments due to incompatibility of methods and barriers such as buildings, roads and private property. Light Detection and Ranging (LiDAR) technology, specifically ALSs, have previously been used to characterize the distribution of snow under forest canopy, and in remote mountain environments. This study investigates and assesses the utility of high resolution, non-intrusive ALS data for estimating the depth and distribution of snow within the town of Uxbridge, Ontario. ALS flights for this study were completed before the onset of snow accumulation, as well as near peak snow accumulation for the winters of 2010 and 2011. Pre and post snow accumulation ALS measured elevations were differenced to estimate the depth of the snowpack across the entire study area at a resolution of 0.5 m. Ground measurements of snow depth were also completed within 24 hours of each of the winter flights. The LiDAR-estimated and ground-measured snow depths were compared using Spearman's rank correlation coefficient as well as Mean Absolute Error (MAE) and Root Mean Squared Error (RMSE). Results from this thesis show that: 1) Snow depths estimated by differencing elevations from two ALS flights show a MAE of 3 cm and an RMSE of 10 cm when compared to ground-measured snow depths. (2) There is a strong, statistically significant relationship (ρ = 0:82, p < 0:001) between LiDAR-estimated and ground-measured snow depths. (3) An average bias of -3 cm was found for the entire dataset showing an underestimation in the LiDAR-estimated snow depths most likely caused by the effects of low lying vegetation on the fall ALS measurements. The results presented in this study demonstrate that ALSs are capable of providing high spatial resolution snow depth estimates within built-up environments. Furthermore, snow depth measurements made using an ALS can be used to increase the current body of knowledge on the distribution and re-distribution of snow within built-up environments. Snow distributions measured by an ALS could also be used for future development and verification of urban hydrological models.

In this work, wet deposition samples were collected at Middle East Technical University campus, Ankara, between December 2000 and May 2002. Snow samples were collected from 50 grids in January, 2001 in Ankara to investigate dry deposition of PAHs. The collected samples were preconcentrated by Solid Phase Extraction and ultrasonic extraction tecniques. Extraction methodologies were improved prior to analysis of samples. Extracted samples were analyzed by Gas Chromotography-Mass Spectrometry for 14 Polycyclic Aromatic Hydrocarbons. Selected Ion Monitoring mode was used throughout the analysis. Phenanthrene, fluoranthene, pyrene and benzo (b+k) fluoranthene were found to be dominant PAHs in wet deposition samples. Seasonal variation of PAHs were observed having higher concentrations in winter period. Meterological parameters were also examined together with PAH concentrations. Contribution of PAHs coming from North East and South West direction were found to be dominant. Wet deposition fluxes were calculated and compared with other urban sites. Wet deposition fluxes are lower than industrial sites and comparable with urban sites in Europe. PAH ratios and factor analysis results demostrated combustion and traffic emissions are major sources of pollutants in the city. Dry deposition of PAHs were invesigated using snow as a natural collecting surface. Dry deposition fluxes calculated using snow surface are compareble with other similar sites. Dry deposition pollution maps of PAHs were drawn by MapInfo software and it was observed that the major pollution regions are the localities where low income families live and low quality coal used for heating purpose. Ratio calculations showed that the central parts of the city is mostly affected from traffic emissions while coal emissions are dominating at the other parts of the city. Factor analysis applied to data set and 6 factors distinquished as coal, soil, traffic, oil combustion, mixed combustion and road dust.

Two versions of SNOW, which are word-oriented stream ciphers proposed by P. Ekdahl and T. Johansson in 2000 and 2002, are studied together with cryptanalytic attacks on the first version. The reported attacks on SNOW1.0 are the &ldquo / guess-and-determine attack&rdquo / s by Hawkes and Rose and the &ldquo / distinguishing attack&rdquo / by Coppersmith, Halevi and Jutla in 2002. A review of the distinguishing attack on SNOW1.0 is given using the approach made by the designers of SNOW in 2002 on another cipher, SOBER-t32. However, since the calculation methods for the complexities of the attack are different, the values found with the method of the designers of SNOW are higher than the ones found by Coppersmith, Halevi and Jutla. The correlations in the finite state machine that make the distinguishing attack possible and how these correlations are affected by the operations in the finite state machine are investigated. Since the substitution boxes (S-boxes) play an important role in destroying the correlation and linearity caused by Linear Feedback Shift Register, the s-boxes of the two versions of SNOW are examined for the criteria of Linear Approximation Table (LAT), Difference Distribution Table (DDT) and Auto-correlation Table distributions. The randomness tests are performed using NIST statistical test suite for both of the ciphers. The results of the tests are presented.

In this work, dry deposition of metals is investigated in an urban area / city of Ankara using snow as a surrogate surface. Two sampling campaigns were conducted to determine dry deposited amount of 13 species namely / H+, Na, K, Al, Mg, Fe, V, Cd, Cr, Cu, Pb, Zn, Ni. First sampling was performed after a major snow fall in Ankara in January 2001, from 4 points according to a predetermined sampling procedure in order to assess background composition of snow. After 12 days, snow samples were collected from 54 points. All samples are filtered, digested and divided into two aliquots in order to investigate soluble and insoluble fractions separately. Temporal changes of snow showed that snow is a good surrogate surface for dry deposition of metals and provide multifunctional informative data. Pollution maps of the city are drawn using Mapinfo software to investigate spatial pollution distributions. Factor analysis are applied and five main factors for these elements are found, indicating three main sources as traffic, soil and combustion. Enrichment factor calculations showed that Ni, Ca, Pb, Zn, Ni, Cu and Cd are highly enriched pointing out the anthropogenic sources affecting the city atmosphere drastically.

No description available.

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.